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![Thadeu Lima de Souza Cascardo](/assets/img/avatar_default.png)
When reading blkio.throttle.io_serviced in a recently created blkio cgroup, it's possible to race against the creation of a throttle policy, which delays the allocation of stats_cpu. Like other functions in the throttle code, just checking for a NULL stats_cpu prevents the following oops caused by that race. [ 1117.285199] Unable to handle kernel paging request for data at address 0x7fb4d0020 [ 1117.285252] Faulting instruction address: 0xc0000000003efa2c [ 1137.733921] Oops: Kernel access of bad area, sig: 11 [#1] [ 1137.733945] SMP NR_CPUS=2048 NUMA PowerNV [ 1137.734025] Modules linked in: bridge stp llc kvm_hv kvm binfmt_misc autofs4 [ 1137.734102] CPU: 3 PID: 5302 Comm: blkcgroup Not tainted 3.19.0 #5 [ 1137.734132] task: c000000f1d188b00 ti: c000000f1d210000 task.ti: c000000f1d210000 [ 1137.734167] NIP: c0000000003efa2c LR: c0000000003ef9f0 CTR: c0000000003ef980 [ 1137.734202] REGS: c000000f1d213500 TRAP: 0300 Not tainted (3.19.0) [ 1137.734230] MSR: 9000000000009032 <SF,HV,EE,ME,IR,DR,RI> CR: 42008884 XER: 20000000 [ 1137.734325] CFAR: 0000000000008458 DAR: 00000007fb4d0020 DSISR: 40000000 SOFTE: 0 GPR00: c0000000003ed3a0 c000000f1d213780 c000000000c59538 0000000000000000 GPR04: 0000000000000800 0000000000000000 0000000000000000 0000000000000000 GPR08: ffffffffffffffff 00000007fb4d0020 00000007fb4d0000 c000000000780808 GPR12: 0000000022000888 c00000000fdc0d80 0000000000000000 0000000000000000 GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 GPR20: 000001003e120200 c000000f1d5b0cc0 0000000000000200 0000000000000000 GPR24: 0000000000000001 c000000000c269e0 0000000000000020 c000000f1d5b0c80 GPR28: c000000000ca3a08 c000000000ca3dec c000000f1c667e00 c000000f1d213850 [ 1137.734886] NIP [c0000000003efa2c] .tg_prfill_cpu_rwstat+0xac/0x180 [ 1137.734915] LR [c0000000003ef9f0] .tg_prfill_cpu_rwstat+0x70/0x180 [ 1137.734943] Call Trace: [ 1137.734952] [c000000f1d213780] [d000000005560520] 0xd000000005560520 (unreliable) [ 1137.734996] [c000000f1d2138a0] [c0000000003ed3a0] .blkcg_print_blkgs+0xe0/0x1a0 [ 1137.735039] [c000000f1d213960] [c0000000003efb50] .tg_print_cpu_rwstat+0x50/0x70 [ 1137.735082] [c000000f1d2139e0] [c000000000104b48] .cgroup_seqfile_show+0x58/0x150 [ 1137.735125] [c000000f1d213a70] [c0000000002749dc] .kernfs_seq_show+0x3c/0x50 [ 1137.735161] [c000000f1d213ae0] [c000000000218630] .seq_read+0xe0/0x510 [ 1137.735197] [c000000f1d213bd0] [c000000000275b04] .kernfs_fop_read+0x164/0x200 [ 1137.735240] [c000000f1d213c80] [c0000000001eb8e0] .__vfs_read+0x30/0x80 [ 1137.735276] [c000000f1d213cf0] [c0000000001eb9c4] .vfs_read+0x94/0x1b0 [ 1137.735312] [c000000f1d213d90] [c0000000001ebb38] .SyS_read+0x58/0x100 [ 1137.735349] [c000000f1d213e30] [c000000000009218] syscall_exit+0x0/0x98 [ 1137.735383] Instruction dump: [ 1137.735405] 7c6307b4 7f891800 409d00b8 60000000 60420000 3d420004 392a63b0 786a1f24 [ 1137.735471] 7d49502a e93e01c8 7d495214 7d2ad214 <7cead02a> e9090008 e9490010 e9290018 And here is one code that allows to easily reproduce this, although this has first been found by running docker. void run(pid_t pid) { int n; int status; int fd; char *buffer; buffer = memalign(BUFFER_ALIGN, BUFFER_SIZE); n = snprintf(buffer, BUFFER_SIZE, "%d\n", pid); fd = open(CGPATH "/test/tasks", O_WRONLY); write(fd, buffer, n); close(fd); if (fork() > 0) { fd = open("/dev/sda", O_RDONLY | O_DIRECT); read(fd, buffer, 512); close(fd); wait(&status); } else { fd = open(CGPATH "/test/blkio.throttle.io_serviced", O_RDONLY); n = read(fd, buffer, BUFFER_SIZE); close(fd); } free(buffer); exit(0); } void test(void) { int status; mkdir(CGPATH "/test", 0666); if (fork() > 0) wait(&status); else run(getpid()); rmdir(CGPATH "/test"); } int main(int argc, char **argv) { int i; for (i = 0; i < NR_TESTS; i++) test(); return 0; } Reported-by: Ricardo Marin Matinata <rmm@br.ibm.com> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com> Cc: stable@vger.kernel.org Signed-off-by: Jens Axboe <axboe@fb.com>
1699 lines
46 KiB
C
1699 lines
46 KiB
C
/*
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* Interface for controlling IO bandwidth on a request queue
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*
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* Copyright (C) 2010 Vivek Goyal <vgoyal@redhat.com>
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*/
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/blkdev.h>
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#include <linux/bio.h>
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#include <linux/blktrace_api.h>
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#include "blk-cgroup.h"
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#include "blk.h"
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/* Max dispatch from a group in 1 round */
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static int throtl_grp_quantum = 8;
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/* Total max dispatch from all groups in one round */
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static int throtl_quantum = 32;
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/* Throttling is performed over 100ms slice and after that slice is renewed */
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static unsigned long throtl_slice = HZ/10; /* 100 ms */
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static struct blkcg_policy blkcg_policy_throtl;
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/* A workqueue to queue throttle related work */
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static struct workqueue_struct *kthrotld_workqueue;
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/*
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* To implement hierarchical throttling, throtl_grps form a tree and bios
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* are dispatched upwards level by level until they reach the top and get
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* issued. When dispatching bios from the children and local group at each
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* level, if the bios are dispatched into a single bio_list, there's a risk
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* of a local or child group which can queue many bios at once filling up
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* the list starving others.
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*
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* To avoid such starvation, dispatched bios are queued separately
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* according to where they came from. When they are again dispatched to
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* the parent, they're popped in round-robin order so that no single source
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* hogs the dispatch window.
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*
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* throtl_qnode is used to keep the queued bios separated by their sources.
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* Bios are queued to throtl_qnode which in turn is queued to
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* throtl_service_queue and then dispatched in round-robin order.
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*
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* It's also used to track the reference counts on blkg's. A qnode always
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* belongs to a throtl_grp and gets queued on itself or the parent, so
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* incrementing the reference of the associated throtl_grp when a qnode is
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* queued and decrementing when dequeued is enough to keep the whole blkg
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* tree pinned while bios are in flight.
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*/
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struct throtl_qnode {
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struct list_head node; /* service_queue->queued[] */
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struct bio_list bios; /* queued bios */
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struct throtl_grp *tg; /* tg this qnode belongs to */
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};
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struct throtl_service_queue {
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struct throtl_service_queue *parent_sq; /* the parent service_queue */
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/*
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* Bios queued directly to this service_queue or dispatched from
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* children throtl_grp's.
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*/
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struct list_head queued[2]; /* throtl_qnode [READ/WRITE] */
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unsigned int nr_queued[2]; /* number of queued bios */
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/*
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* RB tree of active children throtl_grp's, which are sorted by
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* their ->disptime.
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*/
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struct rb_root pending_tree; /* RB tree of active tgs */
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struct rb_node *first_pending; /* first node in the tree */
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unsigned int nr_pending; /* # queued in the tree */
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unsigned long first_pending_disptime; /* disptime of the first tg */
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struct timer_list pending_timer; /* fires on first_pending_disptime */
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};
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enum tg_state_flags {
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THROTL_TG_PENDING = 1 << 0, /* on parent's pending tree */
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THROTL_TG_WAS_EMPTY = 1 << 1, /* bio_lists[] became non-empty */
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};
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#define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
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/* Per-cpu group stats */
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struct tg_stats_cpu {
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/* total bytes transferred */
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struct blkg_rwstat service_bytes;
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/* total IOs serviced, post merge */
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struct blkg_rwstat serviced;
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};
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struct throtl_grp {
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/* must be the first member */
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struct blkg_policy_data pd;
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/* active throtl group service_queue member */
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struct rb_node rb_node;
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/* throtl_data this group belongs to */
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struct throtl_data *td;
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/* this group's service queue */
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struct throtl_service_queue service_queue;
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/*
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* qnode_on_self is used when bios are directly queued to this
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* throtl_grp so that local bios compete fairly with bios
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* dispatched from children. qnode_on_parent is used when bios are
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* dispatched from this throtl_grp into its parent and will compete
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* with the sibling qnode_on_parents and the parent's
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* qnode_on_self.
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*/
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struct throtl_qnode qnode_on_self[2];
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struct throtl_qnode qnode_on_parent[2];
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/*
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* Dispatch time in jiffies. This is the estimated time when group
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* will unthrottle and is ready to dispatch more bio. It is used as
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* key to sort active groups in service tree.
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*/
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unsigned long disptime;
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unsigned int flags;
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/* are there any throtl rules between this group and td? */
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bool has_rules[2];
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/* bytes per second rate limits */
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uint64_t bps[2];
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/* IOPS limits */
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unsigned int iops[2];
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/* Number of bytes disptached in current slice */
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uint64_t bytes_disp[2];
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/* Number of bio's dispatched in current slice */
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unsigned int io_disp[2];
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/* When did we start a new slice */
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unsigned long slice_start[2];
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unsigned long slice_end[2];
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/* Per cpu stats pointer */
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struct tg_stats_cpu __percpu *stats_cpu;
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/* List of tgs waiting for per cpu stats memory to be allocated */
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struct list_head stats_alloc_node;
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};
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struct throtl_data
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{
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/* service tree for active throtl groups */
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struct throtl_service_queue service_queue;
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struct request_queue *queue;
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/* Total Number of queued bios on READ and WRITE lists */
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unsigned int nr_queued[2];
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/*
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* number of total undestroyed groups
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*/
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unsigned int nr_undestroyed_grps;
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/* Work for dispatching throttled bios */
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struct work_struct dispatch_work;
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};
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/* list and work item to allocate percpu group stats */
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static DEFINE_SPINLOCK(tg_stats_alloc_lock);
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static LIST_HEAD(tg_stats_alloc_list);
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static void tg_stats_alloc_fn(struct work_struct *);
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static DECLARE_DELAYED_WORK(tg_stats_alloc_work, tg_stats_alloc_fn);
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static void throtl_pending_timer_fn(unsigned long arg);
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static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
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{
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return pd ? container_of(pd, struct throtl_grp, pd) : NULL;
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}
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static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg)
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{
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return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl));
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}
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static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg)
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{
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return pd_to_blkg(&tg->pd);
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}
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static inline struct throtl_grp *td_root_tg(struct throtl_data *td)
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{
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return blkg_to_tg(td->queue->root_blkg);
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}
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/**
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* sq_to_tg - return the throl_grp the specified service queue belongs to
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* @sq: the throtl_service_queue of interest
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*
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* Return the throtl_grp @sq belongs to. If @sq is the top-level one
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* embedded in throtl_data, %NULL is returned.
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*/
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static struct throtl_grp *sq_to_tg(struct throtl_service_queue *sq)
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{
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if (sq && sq->parent_sq)
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return container_of(sq, struct throtl_grp, service_queue);
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else
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return NULL;
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}
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/**
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* sq_to_td - return throtl_data the specified service queue belongs to
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* @sq: the throtl_service_queue of interest
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*
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* A service_queue can be embeded in either a throtl_grp or throtl_data.
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* Determine the associated throtl_data accordingly and return it.
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*/
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static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
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{
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struct throtl_grp *tg = sq_to_tg(sq);
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if (tg)
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return tg->td;
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else
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return container_of(sq, struct throtl_data, service_queue);
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}
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/**
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* throtl_log - log debug message via blktrace
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* @sq: the service_queue being reported
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* @fmt: printf format string
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* @args: printf args
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*
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* The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a
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* throtl_grp; otherwise, just "throtl".
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*
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* TODO: this should be made a function and name formatting should happen
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* after testing whether blktrace is enabled.
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*/
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#define throtl_log(sq, fmt, args...) do { \
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struct throtl_grp *__tg = sq_to_tg((sq)); \
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struct throtl_data *__td = sq_to_td((sq)); \
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\
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(void)__td; \
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if ((__tg)) { \
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char __pbuf[128]; \
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\
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blkg_path(tg_to_blkg(__tg), __pbuf, sizeof(__pbuf)); \
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blk_add_trace_msg(__td->queue, "throtl %s " fmt, __pbuf, ##args); \
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} else { \
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blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \
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} \
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} while (0)
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static void tg_stats_init(struct tg_stats_cpu *tg_stats)
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{
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blkg_rwstat_init(&tg_stats->service_bytes);
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blkg_rwstat_init(&tg_stats->serviced);
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}
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/*
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* Worker for allocating per cpu stat for tgs. This is scheduled on the
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* system_wq once there are some groups on the alloc_list waiting for
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* allocation.
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*/
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static void tg_stats_alloc_fn(struct work_struct *work)
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{
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static struct tg_stats_cpu *stats_cpu; /* this fn is non-reentrant */
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struct delayed_work *dwork = to_delayed_work(work);
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bool empty = false;
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alloc_stats:
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if (!stats_cpu) {
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int cpu;
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stats_cpu = alloc_percpu(struct tg_stats_cpu);
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if (!stats_cpu) {
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/* allocation failed, try again after some time */
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schedule_delayed_work(dwork, msecs_to_jiffies(10));
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return;
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}
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for_each_possible_cpu(cpu)
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tg_stats_init(per_cpu_ptr(stats_cpu, cpu));
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}
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spin_lock_irq(&tg_stats_alloc_lock);
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if (!list_empty(&tg_stats_alloc_list)) {
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struct throtl_grp *tg = list_first_entry(&tg_stats_alloc_list,
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struct throtl_grp,
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stats_alloc_node);
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swap(tg->stats_cpu, stats_cpu);
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list_del_init(&tg->stats_alloc_node);
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}
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empty = list_empty(&tg_stats_alloc_list);
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spin_unlock_irq(&tg_stats_alloc_lock);
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if (!empty)
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goto alloc_stats;
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}
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static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg)
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{
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INIT_LIST_HEAD(&qn->node);
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bio_list_init(&qn->bios);
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qn->tg = tg;
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}
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/**
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* throtl_qnode_add_bio - add a bio to a throtl_qnode and activate it
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* @bio: bio being added
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* @qn: qnode to add bio to
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* @queued: the service_queue->queued[] list @qn belongs to
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*
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* Add @bio to @qn and put @qn on @queued if it's not already on.
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* @qn->tg's reference count is bumped when @qn is activated. See the
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* comment on top of throtl_qnode definition for details.
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*/
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static void throtl_qnode_add_bio(struct bio *bio, struct throtl_qnode *qn,
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struct list_head *queued)
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{
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bio_list_add(&qn->bios, bio);
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if (list_empty(&qn->node)) {
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list_add_tail(&qn->node, queued);
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blkg_get(tg_to_blkg(qn->tg));
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}
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}
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/**
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* throtl_peek_queued - peek the first bio on a qnode list
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* @queued: the qnode list to peek
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*/
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static struct bio *throtl_peek_queued(struct list_head *queued)
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{
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struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node);
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struct bio *bio;
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if (list_empty(queued))
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return NULL;
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bio = bio_list_peek(&qn->bios);
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WARN_ON_ONCE(!bio);
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return bio;
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}
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/**
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* throtl_pop_queued - pop the first bio form a qnode list
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* @queued: the qnode list to pop a bio from
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* @tg_to_put: optional out argument for throtl_grp to put
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*
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* Pop the first bio from the qnode list @queued. After popping, the first
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* qnode is removed from @queued if empty or moved to the end of @queued so
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* that the popping order is round-robin.
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*
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* When the first qnode is removed, its associated throtl_grp should be put
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* too. If @tg_to_put is NULL, this function automatically puts it;
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* otherwise, *@tg_to_put is set to the throtl_grp to put and the caller is
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* responsible for putting it.
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*/
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static struct bio *throtl_pop_queued(struct list_head *queued,
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struct throtl_grp **tg_to_put)
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{
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struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node);
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struct bio *bio;
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if (list_empty(queued))
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return NULL;
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bio = bio_list_pop(&qn->bios);
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WARN_ON_ONCE(!bio);
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if (bio_list_empty(&qn->bios)) {
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list_del_init(&qn->node);
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if (tg_to_put)
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*tg_to_put = qn->tg;
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else
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blkg_put(tg_to_blkg(qn->tg));
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} else {
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list_move_tail(&qn->node, queued);
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}
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return bio;
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}
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/* init a service_queue, assumes the caller zeroed it */
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static void throtl_service_queue_init(struct throtl_service_queue *sq,
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struct throtl_service_queue *parent_sq)
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{
|
|
INIT_LIST_HEAD(&sq->queued[0]);
|
|
INIT_LIST_HEAD(&sq->queued[1]);
|
|
sq->pending_tree = RB_ROOT;
|
|
sq->parent_sq = parent_sq;
|
|
setup_timer(&sq->pending_timer, throtl_pending_timer_fn,
|
|
(unsigned long)sq);
|
|
}
|
|
|
|
static void throtl_service_queue_exit(struct throtl_service_queue *sq)
|
|
{
|
|
del_timer_sync(&sq->pending_timer);
|
|
}
|
|
|
|
static void throtl_pd_init(struct blkcg_gq *blkg)
|
|
{
|
|
struct throtl_grp *tg = blkg_to_tg(blkg);
|
|
struct throtl_data *td = blkg->q->td;
|
|
struct throtl_service_queue *parent_sq;
|
|
unsigned long flags;
|
|
int rw;
|
|
|
|
/*
|
|
* If on the default hierarchy, we switch to properly hierarchical
|
|
* behavior where limits on a given throtl_grp are applied to the
|
|
* whole subtree rather than just the group itself. e.g. If 16M
|
|
* read_bps limit is set on the root group, the whole system can't
|
|
* exceed 16M for the device.
|
|
*
|
|
* If not on the default hierarchy, the broken flat hierarchy
|
|
* behavior is retained where all throtl_grps are treated as if
|
|
* they're all separate root groups right below throtl_data.
|
|
* Limits of a group don't interact with limits of other groups
|
|
* regardless of the position of the group in the hierarchy.
|
|
*/
|
|
parent_sq = &td->service_queue;
|
|
|
|
if (cgroup_on_dfl(blkg->blkcg->css.cgroup) && blkg->parent)
|
|
parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
|
|
|
|
throtl_service_queue_init(&tg->service_queue, parent_sq);
|
|
|
|
for (rw = READ; rw <= WRITE; rw++) {
|
|
throtl_qnode_init(&tg->qnode_on_self[rw], tg);
|
|
throtl_qnode_init(&tg->qnode_on_parent[rw], tg);
|
|
}
|
|
|
|
RB_CLEAR_NODE(&tg->rb_node);
|
|
tg->td = td;
|
|
|
|
tg->bps[READ] = -1;
|
|
tg->bps[WRITE] = -1;
|
|
tg->iops[READ] = -1;
|
|
tg->iops[WRITE] = -1;
|
|
|
|
/*
|
|
* Ugh... We need to perform per-cpu allocation for tg->stats_cpu
|
|
* but percpu allocator can't be called from IO path. Queue tg on
|
|
* tg_stats_alloc_list and allocate from work item.
|
|
*/
|
|
spin_lock_irqsave(&tg_stats_alloc_lock, flags);
|
|
list_add(&tg->stats_alloc_node, &tg_stats_alloc_list);
|
|
schedule_delayed_work(&tg_stats_alloc_work, 0);
|
|
spin_unlock_irqrestore(&tg_stats_alloc_lock, flags);
|
|
}
|
|
|
|
/*
|
|
* Set has_rules[] if @tg or any of its parents have limits configured.
|
|
* This doesn't require walking up to the top of the hierarchy as the
|
|
* parent's has_rules[] is guaranteed to be correct.
|
|
*/
|
|
static void tg_update_has_rules(struct throtl_grp *tg)
|
|
{
|
|
struct throtl_grp *parent_tg = sq_to_tg(tg->service_queue.parent_sq);
|
|
int rw;
|
|
|
|
for (rw = READ; rw <= WRITE; rw++)
|
|
tg->has_rules[rw] = (parent_tg && parent_tg->has_rules[rw]) ||
|
|
(tg->bps[rw] != -1 || tg->iops[rw] != -1);
|
|
}
|
|
|
|
static void throtl_pd_online(struct blkcg_gq *blkg)
|
|
{
|
|
/*
|
|
* We don't want new groups to escape the limits of its ancestors.
|
|
* Update has_rules[] after a new group is brought online.
|
|
*/
|
|
tg_update_has_rules(blkg_to_tg(blkg));
|
|
}
|
|
|
|
static void throtl_pd_exit(struct blkcg_gq *blkg)
|
|
{
|
|
struct throtl_grp *tg = blkg_to_tg(blkg);
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&tg_stats_alloc_lock, flags);
|
|
list_del_init(&tg->stats_alloc_node);
|
|
spin_unlock_irqrestore(&tg_stats_alloc_lock, flags);
|
|
|
|
free_percpu(tg->stats_cpu);
|
|
|
|
throtl_service_queue_exit(&tg->service_queue);
|
|
}
|
|
|
|
static void throtl_pd_reset_stats(struct blkcg_gq *blkg)
|
|
{
|
|
struct throtl_grp *tg = blkg_to_tg(blkg);
|
|
int cpu;
|
|
|
|
if (tg->stats_cpu == NULL)
|
|
return;
|
|
|
|
for_each_possible_cpu(cpu) {
|
|
struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu);
|
|
|
|
blkg_rwstat_reset(&sc->service_bytes);
|
|
blkg_rwstat_reset(&sc->serviced);
|
|
}
|
|
}
|
|
|
|
static struct throtl_grp *throtl_lookup_tg(struct throtl_data *td,
|
|
struct blkcg *blkcg)
|
|
{
|
|
/*
|
|
* This is the common case when there are no blkcgs. Avoid lookup
|
|
* in this case
|
|
*/
|
|
if (blkcg == &blkcg_root)
|
|
return td_root_tg(td);
|
|
|
|
return blkg_to_tg(blkg_lookup(blkcg, td->queue));
|
|
}
|
|
|
|
static struct throtl_grp *throtl_lookup_create_tg(struct throtl_data *td,
|
|
struct blkcg *blkcg)
|
|
{
|
|
struct request_queue *q = td->queue;
|
|
struct throtl_grp *tg = NULL;
|
|
|
|
/*
|
|
* This is the common case when there are no blkcgs. Avoid lookup
|
|
* in this case
|
|
*/
|
|
if (blkcg == &blkcg_root) {
|
|
tg = td_root_tg(td);
|
|
} else {
|
|
struct blkcg_gq *blkg;
|
|
|
|
blkg = blkg_lookup_create(blkcg, q);
|
|
|
|
/* if %NULL and @q is alive, fall back to root_tg */
|
|
if (!IS_ERR(blkg))
|
|
tg = blkg_to_tg(blkg);
|
|
else if (!blk_queue_dying(q))
|
|
tg = td_root_tg(td);
|
|
}
|
|
|
|
return tg;
|
|
}
|
|
|
|
static struct throtl_grp *
|
|
throtl_rb_first(struct throtl_service_queue *parent_sq)
|
|
{
|
|
/* Service tree is empty */
|
|
if (!parent_sq->nr_pending)
|
|
return NULL;
|
|
|
|
if (!parent_sq->first_pending)
|
|
parent_sq->first_pending = rb_first(&parent_sq->pending_tree);
|
|
|
|
if (parent_sq->first_pending)
|
|
return rb_entry_tg(parent_sq->first_pending);
|
|
|
|
return NULL;
|
|
}
|
|
|
|
static void rb_erase_init(struct rb_node *n, struct rb_root *root)
|
|
{
|
|
rb_erase(n, root);
|
|
RB_CLEAR_NODE(n);
|
|
}
|
|
|
|
static void throtl_rb_erase(struct rb_node *n,
|
|
struct throtl_service_queue *parent_sq)
|
|
{
|
|
if (parent_sq->first_pending == n)
|
|
parent_sq->first_pending = NULL;
|
|
rb_erase_init(n, &parent_sq->pending_tree);
|
|
--parent_sq->nr_pending;
|
|
}
|
|
|
|
static void update_min_dispatch_time(struct throtl_service_queue *parent_sq)
|
|
{
|
|
struct throtl_grp *tg;
|
|
|
|
tg = throtl_rb_first(parent_sq);
|
|
if (!tg)
|
|
return;
|
|
|
|
parent_sq->first_pending_disptime = tg->disptime;
|
|
}
|
|
|
|
static void tg_service_queue_add(struct throtl_grp *tg)
|
|
{
|
|
struct throtl_service_queue *parent_sq = tg->service_queue.parent_sq;
|
|
struct rb_node **node = &parent_sq->pending_tree.rb_node;
|
|
struct rb_node *parent = NULL;
|
|
struct throtl_grp *__tg;
|
|
unsigned long key = tg->disptime;
|
|
int left = 1;
|
|
|
|
while (*node != NULL) {
|
|
parent = *node;
|
|
__tg = rb_entry_tg(parent);
|
|
|
|
if (time_before(key, __tg->disptime))
|
|
node = &parent->rb_left;
|
|
else {
|
|
node = &parent->rb_right;
|
|
left = 0;
|
|
}
|
|
}
|
|
|
|
if (left)
|
|
parent_sq->first_pending = &tg->rb_node;
|
|
|
|
rb_link_node(&tg->rb_node, parent, node);
|
|
rb_insert_color(&tg->rb_node, &parent_sq->pending_tree);
|
|
}
|
|
|
|
static void __throtl_enqueue_tg(struct throtl_grp *tg)
|
|
{
|
|
tg_service_queue_add(tg);
|
|
tg->flags |= THROTL_TG_PENDING;
|
|
tg->service_queue.parent_sq->nr_pending++;
|
|
}
|
|
|
|
static void throtl_enqueue_tg(struct throtl_grp *tg)
|
|
{
|
|
if (!(tg->flags & THROTL_TG_PENDING))
|
|
__throtl_enqueue_tg(tg);
|
|
}
|
|
|
|
static void __throtl_dequeue_tg(struct throtl_grp *tg)
|
|
{
|
|
throtl_rb_erase(&tg->rb_node, tg->service_queue.parent_sq);
|
|
tg->flags &= ~THROTL_TG_PENDING;
|
|
}
|
|
|
|
static void throtl_dequeue_tg(struct throtl_grp *tg)
|
|
{
|
|
if (tg->flags & THROTL_TG_PENDING)
|
|
__throtl_dequeue_tg(tg);
|
|
}
|
|
|
|
/* Call with queue lock held */
|
|
static void throtl_schedule_pending_timer(struct throtl_service_queue *sq,
|
|
unsigned long expires)
|
|
{
|
|
mod_timer(&sq->pending_timer, expires);
|
|
throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu",
|
|
expires - jiffies, jiffies);
|
|
}
|
|
|
|
/**
|
|
* throtl_schedule_next_dispatch - schedule the next dispatch cycle
|
|
* @sq: the service_queue to schedule dispatch for
|
|
* @force: force scheduling
|
|
*
|
|
* Arm @sq->pending_timer so that the next dispatch cycle starts on the
|
|
* dispatch time of the first pending child. Returns %true if either timer
|
|
* is armed or there's no pending child left. %false if the current
|
|
* dispatch window is still open and the caller should continue
|
|
* dispatching.
|
|
*
|
|
* If @force is %true, the dispatch timer is always scheduled and this
|
|
* function is guaranteed to return %true. This is to be used when the
|
|
* caller can't dispatch itself and needs to invoke pending_timer
|
|
* unconditionally. Note that forced scheduling is likely to induce short
|
|
* delay before dispatch starts even if @sq->first_pending_disptime is not
|
|
* in the future and thus shouldn't be used in hot paths.
|
|
*/
|
|
static bool throtl_schedule_next_dispatch(struct throtl_service_queue *sq,
|
|
bool force)
|
|
{
|
|
/* any pending children left? */
|
|
if (!sq->nr_pending)
|
|
return true;
|
|
|
|
update_min_dispatch_time(sq);
|
|
|
|
/* is the next dispatch time in the future? */
|
|
if (force || time_after(sq->first_pending_disptime, jiffies)) {
|
|
throtl_schedule_pending_timer(sq, sq->first_pending_disptime);
|
|
return true;
|
|
}
|
|
|
|
/* tell the caller to continue dispatching */
|
|
return false;
|
|
}
|
|
|
|
static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg,
|
|
bool rw, unsigned long start)
|
|
{
|
|
tg->bytes_disp[rw] = 0;
|
|
tg->io_disp[rw] = 0;
|
|
|
|
/*
|
|
* Previous slice has expired. We must have trimmed it after last
|
|
* bio dispatch. That means since start of last slice, we never used
|
|
* that bandwidth. Do try to make use of that bandwidth while giving
|
|
* credit.
|
|
*/
|
|
if (time_after_eq(start, tg->slice_start[rw]))
|
|
tg->slice_start[rw] = start;
|
|
|
|
tg->slice_end[rw] = jiffies + throtl_slice;
|
|
throtl_log(&tg->service_queue,
|
|
"[%c] new slice with credit start=%lu end=%lu jiffies=%lu",
|
|
rw == READ ? 'R' : 'W', tg->slice_start[rw],
|
|
tg->slice_end[rw], jiffies);
|
|
}
|
|
|
|
static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw)
|
|
{
|
|
tg->bytes_disp[rw] = 0;
|
|
tg->io_disp[rw] = 0;
|
|
tg->slice_start[rw] = jiffies;
|
|
tg->slice_end[rw] = jiffies + throtl_slice;
|
|
throtl_log(&tg->service_queue,
|
|
"[%c] new slice start=%lu end=%lu jiffies=%lu",
|
|
rw == READ ? 'R' : 'W', tg->slice_start[rw],
|
|
tg->slice_end[rw], jiffies);
|
|
}
|
|
|
|
static inline void throtl_set_slice_end(struct throtl_grp *tg, bool rw,
|
|
unsigned long jiffy_end)
|
|
{
|
|
tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
|
|
}
|
|
|
|
static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw,
|
|
unsigned long jiffy_end)
|
|
{
|
|
tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
|
|
throtl_log(&tg->service_queue,
|
|
"[%c] extend slice start=%lu end=%lu jiffies=%lu",
|
|
rw == READ ? 'R' : 'W', tg->slice_start[rw],
|
|
tg->slice_end[rw], jiffies);
|
|
}
|
|
|
|
/* Determine if previously allocated or extended slice is complete or not */
|
|
static bool throtl_slice_used(struct throtl_grp *tg, bool rw)
|
|
{
|
|
if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
|
|
return false;
|
|
|
|
return 1;
|
|
}
|
|
|
|
/* Trim the used slices and adjust slice start accordingly */
|
|
static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
|
|
{
|
|
unsigned long nr_slices, time_elapsed, io_trim;
|
|
u64 bytes_trim, tmp;
|
|
|
|
BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
|
|
|
|
/*
|
|
* If bps are unlimited (-1), then time slice don't get
|
|
* renewed. Don't try to trim the slice if slice is used. A new
|
|
* slice will start when appropriate.
|
|
*/
|
|
if (throtl_slice_used(tg, rw))
|
|
return;
|
|
|
|
/*
|
|
* A bio has been dispatched. Also adjust slice_end. It might happen
|
|
* that initially cgroup limit was very low resulting in high
|
|
* slice_end, but later limit was bumped up and bio was dispached
|
|
* sooner, then we need to reduce slice_end. A high bogus slice_end
|
|
* is bad because it does not allow new slice to start.
|
|
*/
|
|
|
|
throtl_set_slice_end(tg, rw, jiffies + throtl_slice);
|
|
|
|
time_elapsed = jiffies - tg->slice_start[rw];
|
|
|
|
nr_slices = time_elapsed / throtl_slice;
|
|
|
|
if (!nr_slices)
|
|
return;
|
|
tmp = tg->bps[rw] * throtl_slice * nr_slices;
|
|
do_div(tmp, HZ);
|
|
bytes_trim = tmp;
|
|
|
|
io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ;
|
|
|
|
if (!bytes_trim && !io_trim)
|
|
return;
|
|
|
|
if (tg->bytes_disp[rw] >= bytes_trim)
|
|
tg->bytes_disp[rw] -= bytes_trim;
|
|
else
|
|
tg->bytes_disp[rw] = 0;
|
|
|
|
if (tg->io_disp[rw] >= io_trim)
|
|
tg->io_disp[rw] -= io_trim;
|
|
else
|
|
tg->io_disp[rw] = 0;
|
|
|
|
tg->slice_start[rw] += nr_slices * throtl_slice;
|
|
|
|
throtl_log(&tg->service_queue,
|
|
"[%c] trim slice nr=%lu bytes=%llu io=%lu start=%lu end=%lu jiffies=%lu",
|
|
rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
|
|
tg->slice_start[rw], tg->slice_end[rw], jiffies);
|
|
}
|
|
|
|
static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio,
|
|
unsigned long *wait)
|
|
{
|
|
bool rw = bio_data_dir(bio);
|
|
unsigned int io_allowed;
|
|
unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
|
|
u64 tmp;
|
|
|
|
jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
|
|
|
|
/* Slice has just started. Consider one slice interval */
|
|
if (!jiffy_elapsed)
|
|
jiffy_elapsed_rnd = throtl_slice;
|
|
|
|
jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
|
|
|
|
/*
|
|
* jiffy_elapsed_rnd should not be a big value as minimum iops can be
|
|
* 1 then at max jiffy elapsed should be equivalent of 1 second as we
|
|
* will allow dispatch after 1 second and after that slice should
|
|
* have been trimmed.
|
|
*/
|
|
|
|
tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd;
|
|
do_div(tmp, HZ);
|
|
|
|
if (tmp > UINT_MAX)
|
|
io_allowed = UINT_MAX;
|
|
else
|
|
io_allowed = tmp;
|
|
|
|
if (tg->io_disp[rw] + 1 <= io_allowed) {
|
|
if (wait)
|
|
*wait = 0;
|
|
return true;
|
|
}
|
|
|
|
/* Calc approx time to dispatch */
|
|
jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1;
|
|
|
|
if (jiffy_wait > jiffy_elapsed)
|
|
jiffy_wait = jiffy_wait - jiffy_elapsed;
|
|
else
|
|
jiffy_wait = 1;
|
|
|
|
if (wait)
|
|
*wait = jiffy_wait;
|
|
return 0;
|
|
}
|
|
|
|
static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio,
|
|
unsigned long *wait)
|
|
{
|
|
bool rw = bio_data_dir(bio);
|
|
u64 bytes_allowed, extra_bytes, tmp;
|
|
unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
|
|
|
|
jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
|
|
|
|
/* Slice has just started. Consider one slice interval */
|
|
if (!jiffy_elapsed)
|
|
jiffy_elapsed_rnd = throtl_slice;
|
|
|
|
jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
|
|
|
|
tmp = tg->bps[rw] * jiffy_elapsed_rnd;
|
|
do_div(tmp, HZ);
|
|
bytes_allowed = tmp;
|
|
|
|
if (tg->bytes_disp[rw] + bio->bi_iter.bi_size <= bytes_allowed) {
|
|
if (wait)
|
|
*wait = 0;
|
|
return true;
|
|
}
|
|
|
|
/* Calc approx time to dispatch */
|
|
extra_bytes = tg->bytes_disp[rw] + bio->bi_iter.bi_size - bytes_allowed;
|
|
jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]);
|
|
|
|
if (!jiffy_wait)
|
|
jiffy_wait = 1;
|
|
|
|
/*
|
|
* This wait time is without taking into consideration the rounding
|
|
* up we did. Add that time also.
|
|
*/
|
|
jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
|
|
if (wait)
|
|
*wait = jiffy_wait;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Returns whether one can dispatch a bio or not. Also returns approx number
|
|
* of jiffies to wait before this bio is with-in IO rate and can be dispatched
|
|
*/
|
|
static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
|
|
unsigned long *wait)
|
|
{
|
|
bool rw = bio_data_dir(bio);
|
|
unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
|
|
|
|
/*
|
|
* Currently whole state machine of group depends on first bio
|
|
* queued in the group bio list. So one should not be calling
|
|
* this function with a different bio if there are other bios
|
|
* queued.
|
|
*/
|
|
BUG_ON(tg->service_queue.nr_queued[rw] &&
|
|
bio != throtl_peek_queued(&tg->service_queue.queued[rw]));
|
|
|
|
/* If tg->bps = -1, then BW is unlimited */
|
|
if (tg->bps[rw] == -1 && tg->iops[rw] == -1) {
|
|
if (wait)
|
|
*wait = 0;
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* If previous slice expired, start a new one otherwise renew/extend
|
|
* existing slice to make sure it is at least throtl_slice interval
|
|
* long since now.
|
|
*/
|
|
if (throtl_slice_used(tg, rw))
|
|
throtl_start_new_slice(tg, rw);
|
|
else {
|
|
if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
|
|
throtl_extend_slice(tg, rw, jiffies + throtl_slice);
|
|
}
|
|
|
|
if (tg_with_in_bps_limit(tg, bio, &bps_wait) &&
|
|
tg_with_in_iops_limit(tg, bio, &iops_wait)) {
|
|
if (wait)
|
|
*wait = 0;
|
|
return 1;
|
|
}
|
|
|
|
max_wait = max(bps_wait, iops_wait);
|
|
|
|
if (wait)
|
|
*wait = max_wait;
|
|
|
|
if (time_before(tg->slice_end[rw], jiffies + max_wait))
|
|
throtl_extend_slice(tg, rw, jiffies + max_wait);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void throtl_update_dispatch_stats(struct blkcg_gq *blkg, u64 bytes,
|
|
int rw)
|
|
{
|
|
struct throtl_grp *tg = blkg_to_tg(blkg);
|
|
struct tg_stats_cpu *stats_cpu;
|
|
unsigned long flags;
|
|
|
|
/* If per cpu stats are not allocated yet, don't do any accounting. */
|
|
if (tg->stats_cpu == NULL)
|
|
return;
|
|
|
|
/*
|
|
* Disabling interrupts to provide mutual exclusion between two
|
|
* writes on same cpu. It probably is not needed for 64bit. Not
|
|
* optimizing that case yet.
|
|
*/
|
|
local_irq_save(flags);
|
|
|
|
stats_cpu = this_cpu_ptr(tg->stats_cpu);
|
|
|
|
blkg_rwstat_add(&stats_cpu->serviced, rw, 1);
|
|
blkg_rwstat_add(&stats_cpu->service_bytes, rw, bytes);
|
|
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
|
|
{
|
|
bool rw = bio_data_dir(bio);
|
|
|
|
/* Charge the bio to the group */
|
|
tg->bytes_disp[rw] += bio->bi_iter.bi_size;
|
|
tg->io_disp[rw]++;
|
|
|
|
/*
|
|
* REQ_THROTTLED is used to prevent the same bio to be throttled
|
|
* more than once as a throttled bio will go through blk-throtl the
|
|
* second time when it eventually gets issued. Set it when a bio
|
|
* is being charged to a tg.
|
|
*
|
|
* Dispatch stats aren't recursive and each @bio should only be
|
|
* accounted by the @tg it was originally associated with. Let's
|
|
* update the stats when setting REQ_THROTTLED for the first time
|
|
* which is guaranteed to be for the @bio's original tg.
|
|
*/
|
|
if (!(bio->bi_rw & REQ_THROTTLED)) {
|
|
bio->bi_rw |= REQ_THROTTLED;
|
|
throtl_update_dispatch_stats(tg_to_blkg(tg),
|
|
bio->bi_iter.bi_size, bio->bi_rw);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* throtl_add_bio_tg - add a bio to the specified throtl_grp
|
|
* @bio: bio to add
|
|
* @qn: qnode to use
|
|
* @tg: the target throtl_grp
|
|
*
|
|
* Add @bio to @tg's service_queue using @qn. If @qn is not specified,
|
|
* tg->qnode_on_self[] is used.
|
|
*/
|
|
static void throtl_add_bio_tg(struct bio *bio, struct throtl_qnode *qn,
|
|
struct throtl_grp *tg)
|
|
{
|
|
struct throtl_service_queue *sq = &tg->service_queue;
|
|
bool rw = bio_data_dir(bio);
|
|
|
|
if (!qn)
|
|
qn = &tg->qnode_on_self[rw];
|
|
|
|
/*
|
|
* If @tg doesn't currently have any bios queued in the same
|
|
* direction, queueing @bio can change when @tg should be
|
|
* dispatched. Mark that @tg was empty. This is automatically
|
|
* cleaered on the next tg_update_disptime().
|
|
*/
|
|
if (!sq->nr_queued[rw])
|
|
tg->flags |= THROTL_TG_WAS_EMPTY;
|
|
|
|
throtl_qnode_add_bio(bio, qn, &sq->queued[rw]);
|
|
|
|
sq->nr_queued[rw]++;
|
|
throtl_enqueue_tg(tg);
|
|
}
|
|
|
|
static void tg_update_disptime(struct throtl_grp *tg)
|
|
{
|
|
struct throtl_service_queue *sq = &tg->service_queue;
|
|
unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
|
|
struct bio *bio;
|
|
|
|
if ((bio = throtl_peek_queued(&sq->queued[READ])))
|
|
tg_may_dispatch(tg, bio, &read_wait);
|
|
|
|
if ((bio = throtl_peek_queued(&sq->queued[WRITE])))
|
|
tg_may_dispatch(tg, bio, &write_wait);
|
|
|
|
min_wait = min(read_wait, write_wait);
|
|
disptime = jiffies + min_wait;
|
|
|
|
/* Update dispatch time */
|
|
throtl_dequeue_tg(tg);
|
|
tg->disptime = disptime;
|
|
throtl_enqueue_tg(tg);
|
|
|
|
/* see throtl_add_bio_tg() */
|
|
tg->flags &= ~THROTL_TG_WAS_EMPTY;
|
|
}
|
|
|
|
static void start_parent_slice_with_credit(struct throtl_grp *child_tg,
|
|
struct throtl_grp *parent_tg, bool rw)
|
|
{
|
|
if (throtl_slice_used(parent_tg, rw)) {
|
|
throtl_start_new_slice_with_credit(parent_tg, rw,
|
|
child_tg->slice_start[rw]);
|
|
}
|
|
|
|
}
|
|
|
|
static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw)
|
|
{
|
|
struct throtl_service_queue *sq = &tg->service_queue;
|
|
struct throtl_service_queue *parent_sq = sq->parent_sq;
|
|
struct throtl_grp *parent_tg = sq_to_tg(parent_sq);
|
|
struct throtl_grp *tg_to_put = NULL;
|
|
struct bio *bio;
|
|
|
|
/*
|
|
* @bio is being transferred from @tg to @parent_sq. Popping a bio
|
|
* from @tg may put its reference and @parent_sq might end up
|
|
* getting released prematurely. Remember the tg to put and put it
|
|
* after @bio is transferred to @parent_sq.
|
|
*/
|
|
bio = throtl_pop_queued(&sq->queued[rw], &tg_to_put);
|
|
sq->nr_queued[rw]--;
|
|
|
|
throtl_charge_bio(tg, bio);
|
|
|
|
/*
|
|
* If our parent is another tg, we just need to transfer @bio to
|
|
* the parent using throtl_add_bio_tg(). If our parent is
|
|
* @td->service_queue, @bio is ready to be issued. Put it on its
|
|
* bio_lists[] and decrease total number queued. The caller is
|
|
* responsible for issuing these bios.
|
|
*/
|
|
if (parent_tg) {
|
|
throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg);
|
|
start_parent_slice_with_credit(tg, parent_tg, rw);
|
|
} else {
|
|
throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw],
|
|
&parent_sq->queued[rw]);
|
|
BUG_ON(tg->td->nr_queued[rw] <= 0);
|
|
tg->td->nr_queued[rw]--;
|
|
}
|
|
|
|
throtl_trim_slice(tg, rw);
|
|
|
|
if (tg_to_put)
|
|
blkg_put(tg_to_blkg(tg_to_put));
|
|
}
|
|
|
|
static int throtl_dispatch_tg(struct throtl_grp *tg)
|
|
{
|
|
struct throtl_service_queue *sq = &tg->service_queue;
|
|
unsigned int nr_reads = 0, nr_writes = 0;
|
|
unsigned int max_nr_reads = throtl_grp_quantum*3/4;
|
|
unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads;
|
|
struct bio *bio;
|
|
|
|
/* Try to dispatch 75% READS and 25% WRITES */
|
|
|
|
while ((bio = throtl_peek_queued(&sq->queued[READ])) &&
|
|
tg_may_dispatch(tg, bio, NULL)) {
|
|
|
|
tg_dispatch_one_bio(tg, bio_data_dir(bio));
|
|
nr_reads++;
|
|
|
|
if (nr_reads >= max_nr_reads)
|
|
break;
|
|
}
|
|
|
|
while ((bio = throtl_peek_queued(&sq->queued[WRITE])) &&
|
|
tg_may_dispatch(tg, bio, NULL)) {
|
|
|
|
tg_dispatch_one_bio(tg, bio_data_dir(bio));
|
|
nr_writes++;
|
|
|
|
if (nr_writes >= max_nr_writes)
|
|
break;
|
|
}
|
|
|
|
return nr_reads + nr_writes;
|
|
}
|
|
|
|
static int throtl_select_dispatch(struct throtl_service_queue *parent_sq)
|
|
{
|
|
unsigned int nr_disp = 0;
|
|
|
|
while (1) {
|
|
struct throtl_grp *tg = throtl_rb_first(parent_sq);
|
|
struct throtl_service_queue *sq = &tg->service_queue;
|
|
|
|
if (!tg)
|
|
break;
|
|
|
|
if (time_before(jiffies, tg->disptime))
|
|
break;
|
|
|
|
throtl_dequeue_tg(tg);
|
|
|
|
nr_disp += throtl_dispatch_tg(tg);
|
|
|
|
if (sq->nr_queued[0] || sq->nr_queued[1])
|
|
tg_update_disptime(tg);
|
|
|
|
if (nr_disp >= throtl_quantum)
|
|
break;
|
|
}
|
|
|
|
return nr_disp;
|
|
}
|
|
|
|
/**
|
|
* throtl_pending_timer_fn - timer function for service_queue->pending_timer
|
|
* @arg: the throtl_service_queue being serviced
|
|
*
|
|
* This timer is armed when a child throtl_grp with active bio's become
|
|
* pending and queued on the service_queue's pending_tree and expires when
|
|
* the first child throtl_grp should be dispatched. This function
|
|
* dispatches bio's from the children throtl_grps to the parent
|
|
* service_queue.
|
|
*
|
|
* If the parent's parent is another throtl_grp, dispatching is propagated
|
|
* by either arming its pending_timer or repeating dispatch directly. If
|
|
* the top-level service_tree is reached, throtl_data->dispatch_work is
|
|
* kicked so that the ready bio's are issued.
|
|
*/
|
|
static void throtl_pending_timer_fn(unsigned long arg)
|
|
{
|
|
struct throtl_service_queue *sq = (void *)arg;
|
|
struct throtl_grp *tg = sq_to_tg(sq);
|
|
struct throtl_data *td = sq_to_td(sq);
|
|
struct request_queue *q = td->queue;
|
|
struct throtl_service_queue *parent_sq;
|
|
bool dispatched;
|
|
int ret;
|
|
|
|
spin_lock_irq(q->queue_lock);
|
|
again:
|
|
parent_sq = sq->parent_sq;
|
|
dispatched = false;
|
|
|
|
while (true) {
|
|
throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u",
|
|
sq->nr_queued[READ] + sq->nr_queued[WRITE],
|
|
sq->nr_queued[READ], sq->nr_queued[WRITE]);
|
|
|
|
ret = throtl_select_dispatch(sq);
|
|
if (ret) {
|
|
throtl_log(sq, "bios disp=%u", ret);
|
|
dispatched = true;
|
|
}
|
|
|
|
if (throtl_schedule_next_dispatch(sq, false))
|
|
break;
|
|
|
|
/* this dispatch windows is still open, relax and repeat */
|
|
spin_unlock_irq(q->queue_lock);
|
|
cpu_relax();
|
|
spin_lock_irq(q->queue_lock);
|
|
}
|
|
|
|
if (!dispatched)
|
|
goto out_unlock;
|
|
|
|
if (parent_sq) {
|
|
/* @parent_sq is another throl_grp, propagate dispatch */
|
|
if (tg->flags & THROTL_TG_WAS_EMPTY) {
|
|
tg_update_disptime(tg);
|
|
if (!throtl_schedule_next_dispatch(parent_sq, false)) {
|
|
/* window is already open, repeat dispatching */
|
|
sq = parent_sq;
|
|
tg = sq_to_tg(sq);
|
|
goto again;
|
|
}
|
|
}
|
|
} else {
|
|
/* reached the top-level, queue issueing */
|
|
queue_work(kthrotld_workqueue, &td->dispatch_work);
|
|
}
|
|
out_unlock:
|
|
spin_unlock_irq(q->queue_lock);
|
|
}
|
|
|
|
/**
|
|
* blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work
|
|
* @work: work item being executed
|
|
*
|
|
* This function is queued for execution when bio's reach the bio_lists[]
|
|
* of throtl_data->service_queue. Those bio's are ready and issued by this
|
|
* function.
|
|
*/
|
|
static void blk_throtl_dispatch_work_fn(struct work_struct *work)
|
|
{
|
|
struct throtl_data *td = container_of(work, struct throtl_data,
|
|
dispatch_work);
|
|
struct throtl_service_queue *td_sq = &td->service_queue;
|
|
struct request_queue *q = td->queue;
|
|
struct bio_list bio_list_on_stack;
|
|
struct bio *bio;
|
|
struct blk_plug plug;
|
|
int rw;
|
|
|
|
bio_list_init(&bio_list_on_stack);
|
|
|
|
spin_lock_irq(q->queue_lock);
|
|
for (rw = READ; rw <= WRITE; rw++)
|
|
while ((bio = throtl_pop_queued(&td_sq->queued[rw], NULL)))
|
|
bio_list_add(&bio_list_on_stack, bio);
|
|
spin_unlock_irq(q->queue_lock);
|
|
|
|
if (!bio_list_empty(&bio_list_on_stack)) {
|
|
blk_start_plug(&plug);
|
|
while((bio = bio_list_pop(&bio_list_on_stack)))
|
|
generic_make_request(bio);
|
|
blk_finish_plug(&plug);
|
|
}
|
|
}
|
|
|
|
static u64 tg_prfill_cpu_rwstat(struct seq_file *sf,
|
|
struct blkg_policy_data *pd, int off)
|
|
{
|
|
struct throtl_grp *tg = pd_to_tg(pd);
|
|
struct blkg_rwstat rwstat = { }, tmp;
|
|
int i, cpu;
|
|
|
|
if (tg->stats_cpu == NULL)
|
|
return 0;
|
|
|
|
for_each_possible_cpu(cpu) {
|
|
struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu);
|
|
|
|
tmp = blkg_rwstat_read((void *)sc + off);
|
|
for (i = 0; i < BLKG_RWSTAT_NR; i++)
|
|
rwstat.cnt[i] += tmp.cnt[i];
|
|
}
|
|
|
|
return __blkg_prfill_rwstat(sf, pd, &rwstat);
|
|
}
|
|
|
|
static int tg_print_cpu_rwstat(struct seq_file *sf, void *v)
|
|
{
|
|
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_cpu_rwstat,
|
|
&blkcg_policy_throtl, seq_cft(sf)->private, true);
|
|
return 0;
|
|
}
|
|
|
|
static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd,
|
|
int off)
|
|
{
|
|
struct throtl_grp *tg = pd_to_tg(pd);
|
|
u64 v = *(u64 *)((void *)tg + off);
|
|
|
|
if (v == -1)
|
|
return 0;
|
|
return __blkg_prfill_u64(sf, pd, v);
|
|
}
|
|
|
|
static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd,
|
|
int off)
|
|
{
|
|
struct throtl_grp *tg = pd_to_tg(pd);
|
|
unsigned int v = *(unsigned int *)((void *)tg + off);
|
|
|
|
if (v == -1)
|
|
return 0;
|
|
return __blkg_prfill_u64(sf, pd, v);
|
|
}
|
|
|
|
static int tg_print_conf_u64(struct seq_file *sf, void *v)
|
|
{
|
|
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_u64,
|
|
&blkcg_policy_throtl, seq_cft(sf)->private, false);
|
|
return 0;
|
|
}
|
|
|
|
static int tg_print_conf_uint(struct seq_file *sf, void *v)
|
|
{
|
|
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_uint,
|
|
&blkcg_policy_throtl, seq_cft(sf)->private, false);
|
|
return 0;
|
|
}
|
|
|
|
static ssize_t tg_set_conf(struct kernfs_open_file *of,
|
|
char *buf, size_t nbytes, loff_t off, bool is_u64)
|
|
{
|
|
struct blkcg *blkcg = css_to_blkcg(of_css(of));
|
|
struct blkg_conf_ctx ctx;
|
|
struct throtl_grp *tg;
|
|
struct throtl_service_queue *sq;
|
|
struct blkcg_gq *blkg;
|
|
struct cgroup_subsys_state *pos_css;
|
|
int ret;
|
|
|
|
ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
|
|
if (ret)
|
|
return ret;
|
|
|
|
tg = blkg_to_tg(ctx.blkg);
|
|
sq = &tg->service_queue;
|
|
|
|
if (!ctx.v)
|
|
ctx.v = -1;
|
|
|
|
if (is_u64)
|
|
*(u64 *)((void *)tg + of_cft(of)->private) = ctx.v;
|
|
else
|
|
*(unsigned int *)((void *)tg + of_cft(of)->private) = ctx.v;
|
|
|
|
throtl_log(&tg->service_queue,
|
|
"limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
|
|
tg->bps[READ], tg->bps[WRITE],
|
|
tg->iops[READ], tg->iops[WRITE]);
|
|
|
|
/*
|
|
* Update has_rules[] flags for the updated tg's subtree. A tg is
|
|
* considered to have rules if either the tg itself or any of its
|
|
* ancestors has rules. This identifies groups without any
|
|
* restrictions in the whole hierarchy and allows them to bypass
|
|
* blk-throttle.
|
|
*/
|
|
blkg_for_each_descendant_pre(blkg, pos_css, ctx.blkg)
|
|
tg_update_has_rules(blkg_to_tg(blkg));
|
|
|
|
/*
|
|
* We're already holding queue_lock and know @tg is valid. Let's
|
|
* apply the new config directly.
|
|
*
|
|
* Restart the slices for both READ and WRITES. It might happen
|
|
* that a group's limit are dropped suddenly and we don't want to
|
|
* account recently dispatched IO with new low rate.
|
|
*/
|
|
throtl_start_new_slice(tg, 0);
|
|
throtl_start_new_slice(tg, 1);
|
|
|
|
if (tg->flags & THROTL_TG_PENDING) {
|
|
tg_update_disptime(tg);
|
|
throtl_schedule_next_dispatch(sq->parent_sq, true);
|
|
}
|
|
|
|
blkg_conf_finish(&ctx);
|
|
return nbytes;
|
|
}
|
|
|
|
static ssize_t tg_set_conf_u64(struct kernfs_open_file *of,
|
|
char *buf, size_t nbytes, loff_t off)
|
|
{
|
|
return tg_set_conf(of, buf, nbytes, off, true);
|
|
}
|
|
|
|
static ssize_t tg_set_conf_uint(struct kernfs_open_file *of,
|
|
char *buf, size_t nbytes, loff_t off)
|
|
{
|
|
return tg_set_conf(of, buf, nbytes, off, false);
|
|
}
|
|
|
|
static struct cftype throtl_files[] = {
|
|
{
|
|
.name = "throttle.read_bps_device",
|
|
.private = offsetof(struct throtl_grp, bps[READ]),
|
|
.seq_show = tg_print_conf_u64,
|
|
.write = tg_set_conf_u64,
|
|
},
|
|
{
|
|
.name = "throttle.write_bps_device",
|
|
.private = offsetof(struct throtl_grp, bps[WRITE]),
|
|
.seq_show = tg_print_conf_u64,
|
|
.write = tg_set_conf_u64,
|
|
},
|
|
{
|
|
.name = "throttle.read_iops_device",
|
|
.private = offsetof(struct throtl_grp, iops[READ]),
|
|
.seq_show = tg_print_conf_uint,
|
|
.write = tg_set_conf_uint,
|
|
},
|
|
{
|
|
.name = "throttle.write_iops_device",
|
|
.private = offsetof(struct throtl_grp, iops[WRITE]),
|
|
.seq_show = tg_print_conf_uint,
|
|
.write = tg_set_conf_uint,
|
|
},
|
|
{
|
|
.name = "throttle.io_service_bytes",
|
|
.private = offsetof(struct tg_stats_cpu, service_bytes),
|
|
.seq_show = tg_print_cpu_rwstat,
|
|
},
|
|
{
|
|
.name = "throttle.io_serviced",
|
|
.private = offsetof(struct tg_stats_cpu, serviced),
|
|
.seq_show = tg_print_cpu_rwstat,
|
|
},
|
|
{ } /* terminate */
|
|
};
|
|
|
|
static void throtl_shutdown_wq(struct request_queue *q)
|
|
{
|
|
struct throtl_data *td = q->td;
|
|
|
|
cancel_work_sync(&td->dispatch_work);
|
|
}
|
|
|
|
static struct blkcg_policy blkcg_policy_throtl = {
|
|
.pd_size = sizeof(struct throtl_grp),
|
|
.cftypes = throtl_files,
|
|
|
|
.pd_init_fn = throtl_pd_init,
|
|
.pd_online_fn = throtl_pd_online,
|
|
.pd_exit_fn = throtl_pd_exit,
|
|
.pd_reset_stats_fn = throtl_pd_reset_stats,
|
|
};
|
|
|
|
bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
|
|
{
|
|
struct throtl_data *td = q->td;
|
|
struct throtl_qnode *qn = NULL;
|
|
struct throtl_grp *tg;
|
|
struct throtl_service_queue *sq;
|
|
bool rw = bio_data_dir(bio);
|
|
struct blkcg *blkcg;
|
|
bool throttled = false;
|
|
|
|
/* see throtl_charge_bio() */
|
|
if (bio->bi_rw & REQ_THROTTLED)
|
|
goto out;
|
|
|
|
/*
|
|
* A throtl_grp pointer retrieved under rcu can be used to access
|
|
* basic fields like stats and io rates. If a group has no rules,
|
|
* just update the dispatch stats in lockless manner and return.
|
|
*/
|
|
rcu_read_lock();
|
|
blkcg = bio_blkcg(bio);
|
|
tg = throtl_lookup_tg(td, blkcg);
|
|
if (tg) {
|
|
if (!tg->has_rules[rw]) {
|
|
throtl_update_dispatch_stats(tg_to_blkg(tg),
|
|
bio->bi_iter.bi_size, bio->bi_rw);
|
|
goto out_unlock_rcu;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Either group has not been allocated yet or it is not an unlimited
|
|
* IO group
|
|
*/
|
|
spin_lock_irq(q->queue_lock);
|
|
tg = throtl_lookup_create_tg(td, blkcg);
|
|
if (unlikely(!tg))
|
|
goto out_unlock;
|
|
|
|
sq = &tg->service_queue;
|
|
|
|
while (true) {
|
|
/* throtl is FIFO - if bios are already queued, should queue */
|
|
if (sq->nr_queued[rw])
|
|
break;
|
|
|
|
/* if above limits, break to queue */
|
|
if (!tg_may_dispatch(tg, bio, NULL))
|
|
break;
|
|
|
|
/* within limits, let's charge and dispatch directly */
|
|
throtl_charge_bio(tg, bio);
|
|
|
|
/*
|
|
* We need to trim slice even when bios are not being queued
|
|
* otherwise it might happen that a bio is not queued for
|
|
* a long time and slice keeps on extending and trim is not
|
|
* called for a long time. Now if limits are reduced suddenly
|
|
* we take into account all the IO dispatched so far at new
|
|
* low rate and * newly queued IO gets a really long dispatch
|
|
* time.
|
|
*
|
|
* So keep on trimming slice even if bio is not queued.
|
|
*/
|
|
throtl_trim_slice(tg, rw);
|
|
|
|
/*
|
|
* @bio passed through this layer without being throttled.
|
|
* Climb up the ladder. If we''re already at the top, it
|
|
* can be executed directly.
|
|
*/
|
|
qn = &tg->qnode_on_parent[rw];
|
|
sq = sq->parent_sq;
|
|
tg = sq_to_tg(sq);
|
|
if (!tg)
|
|
goto out_unlock;
|
|
}
|
|
|
|
/* out-of-limit, queue to @tg */
|
|
throtl_log(sq, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d",
|
|
rw == READ ? 'R' : 'W',
|
|
tg->bytes_disp[rw], bio->bi_iter.bi_size, tg->bps[rw],
|
|
tg->io_disp[rw], tg->iops[rw],
|
|
sq->nr_queued[READ], sq->nr_queued[WRITE]);
|
|
|
|
bio_associate_current(bio);
|
|
tg->td->nr_queued[rw]++;
|
|
throtl_add_bio_tg(bio, qn, tg);
|
|
throttled = true;
|
|
|
|
/*
|
|
* Update @tg's dispatch time and force schedule dispatch if @tg
|
|
* was empty before @bio. The forced scheduling isn't likely to
|
|
* cause undue delay as @bio is likely to be dispatched directly if
|
|
* its @tg's disptime is not in the future.
|
|
*/
|
|
if (tg->flags & THROTL_TG_WAS_EMPTY) {
|
|
tg_update_disptime(tg);
|
|
throtl_schedule_next_dispatch(tg->service_queue.parent_sq, true);
|
|
}
|
|
|
|
out_unlock:
|
|
spin_unlock_irq(q->queue_lock);
|
|
out_unlock_rcu:
|
|
rcu_read_unlock();
|
|
out:
|
|
/*
|
|
* As multiple blk-throtls may stack in the same issue path, we
|
|
* don't want bios to leave with the flag set. Clear the flag if
|
|
* being issued.
|
|
*/
|
|
if (!throttled)
|
|
bio->bi_rw &= ~REQ_THROTTLED;
|
|
return throttled;
|
|
}
|
|
|
|
/*
|
|
* Dispatch all bios from all children tg's queued on @parent_sq. On
|
|
* return, @parent_sq is guaranteed to not have any active children tg's
|
|
* and all bios from previously active tg's are on @parent_sq->bio_lists[].
|
|
*/
|
|
static void tg_drain_bios(struct throtl_service_queue *parent_sq)
|
|
{
|
|
struct throtl_grp *tg;
|
|
|
|
while ((tg = throtl_rb_first(parent_sq))) {
|
|
struct throtl_service_queue *sq = &tg->service_queue;
|
|
struct bio *bio;
|
|
|
|
throtl_dequeue_tg(tg);
|
|
|
|
while ((bio = throtl_peek_queued(&sq->queued[READ])))
|
|
tg_dispatch_one_bio(tg, bio_data_dir(bio));
|
|
while ((bio = throtl_peek_queued(&sq->queued[WRITE])))
|
|
tg_dispatch_one_bio(tg, bio_data_dir(bio));
|
|
}
|
|
}
|
|
|
|
/**
|
|
* blk_throtl_drain - drain throttled bios
|
|
* @q: request_queue to drain throttled bios for
|
|
*
|
|
* Dispatch all currently throttled bios on @q through ->make_request_fn().
|
|
*/
|
|
void blk_throtl_drain(struct request_queue *q)
|
|
__releases(q->queue_lock) __acquires(q->queue_lock)
|
|
{
|
|
struct throtl_data *td = q->td;
|
|
struct blkcg_gq *blkg;
|
|
struct cgroup_subsys_state *pos_css;
|
|
struct bio *bio;
|
|
int rw;
|
|
|
|
queue_lockdep_assert_held(q);
|
|
rcu_read_lock();
|
|
|
|
/*
|
|
* Drain each tg while doing post-order walk on the blkg tree, so
|
|
* that all bios are propagated to td->service_queue. It'd be
|
|
* better to walk service_queue tree directly but blkg walk is
|
|
* easier.
|
|
*/
|
|
blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg)
|
|
tg_drain_bios(&blkg_to_tg(blkg)->service_queue);
|
|
|
|
/* finally, transfer bios from top-level tg's into the td */
|
|
tg_drain_bios(&td->service_queue);
|
|
|
|
rcu_read_unlock();
|
|
spin_unlock_irq(q->queue_lock);
|
|
|
|
/* all bios now should be in td->service_queue, issue them */
|
|
for (rw = READ; rw <= WRITE; rw++)
|
|
while ((bio = throtl_pop_queued(&td->service_queue.queued[rw],
|
|
NULL)))
|
|
generic_make_request(bio);
|
|
|
|
spin_lock_irq(q->queue_lock);
|
|
}
|
|
|
|
int blk_throtl_init(struct request_queue *q)
|
|
{
|
|
struct throtl_data *td;
|
|
int ret;
|
|
|
|
td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
|
|
if (!td)
|
|
return -ENOMEM;
|
|
|
|
INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
|
|
throtl_service_queue_init(&td->service_queue, NULL);
|
|
|
|
q->td = td;
|
|
td->queue = q;
|
|
|
|
/* activate policy */
|
|
ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
|
|
if (ret)
|
|
kfree(td);
|
|
return ret;
|
|
}
|
|
|
|
void blk_throtl_exit(struct request_queue *q)
|
|
{
|
|
BUG_ON(!q->td);
|
|
throtl_shutdown_wq(q);
|
|
blkcg_deactivate_policy(q, &blkcg_policy_throtl);
|
|
kfree(q->td);
|
|
}
|
|
|
|
static int __init throtl_init(void)
|
|
{
|
|
kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
|
|
if (!kthrotld_workqueue)
|
|
panic("Failed to create kthrotld\n");
|
|
|
|
return blkcg_policy_register(&blkcg_policy_throtl);
|
|
}
|
|
|
|
module_init(throtl_init);
|