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![Darrick J. Wong](/assets/img/avatar_default.png)
This patchset ("stable page writes, part 2") makes some key modifications to the original 'stable page writes' patchset. First, it provides creators (devices and filesystems) of a backing_dev_info a flag that declares whether or not it is necessary to ensure that page contents cannot change during writeout. It is no longer assumed that this is true of all devices (which was never true anyway). Second, the flag is used to relaxed the wait_on_page_writeback calls so that wait only occurs if the device needs it. Third, it fixes up the remaining disk-backed filesystems to use this improved conditional-wait logic to provide stable page writes on those filesystems. It is hoped that (for people not using checksumming devices, anyway) this patchset will give back unnecessary performance decreases since the original stable page write patchset went into 3.0. Sorry about not fixing it sooner. Complaints were registered by several people about the long write latencies introduced by the original stable page write patchset. Generally speaking, the kernel ought to allocate as little extra memory as possible to facilitate writeout, but for people who simply cannot wait, a second page stability strategy is (re)introduced: snapshotting page contents. The waiting behavior is still the default strategy; to enable page snapshotting, a superblock flag (MS_SNAP_STABLE) must be set. This flag is used to bandaid^Henable stable page writeback on ext3[1], and is not used anywhere else. Given that there are already a few storage devices and network FSes that have rolled their own page stability wait/page snapshot code, it would be nice to move towards consolidating all of these. It seems possible that iscsi and raid5 may wish to use the new stable page write support to enable zero-copy writeout. Thank you to Jan Kara for helping fix a couple more filesystems. Per Andrew Morton's request, here are the result of using dbench to measure latencies on ext2: 3.8.0-rc3: Operation Count AvgLat MaxLat ---------------------------------------- WriteX 109347 0.028 59.817 ReadX 347180 0.004 3.391 Flush 15514 29.828 287.283 Throughput 57.429 MB/sec 4 clients 4 procs max_latency=287.290 ms 3.8.0-rc3 + patches: WriteX 105556 0.029 4.273 ReadX 335004 0.005 4.112 Flush 14982 30.540 298.634 Throughput 55.4496 MB/sec 4 clients 4 procs max_latency=298.650 ms As you can see, for ext2 the maximum write latency decreases from ~60ms on a laptop hard disk to ~4ms. I'm not sure why the flush latencies increase, though I suspect that being able to dirty pages faster gives the flusher more work to do. On ext4, the average write latency decreases as well as all the maximum latencies: 3.8.0-rc3: WriteX 85624 0.152 33.078 ReadX 272090 0.010 61.210 Flush 12129 36.219 168.260 Throughput 44.8618 MB/sec 4 clients 4 procs max_latency=168.276 ms 3.8.0-rc3 + patches: WriteX 86082 0.141 30.928 ReadX 273358 0.010 36.124 Flush 12214 34.800 165.689 Throughput 44.9941 MB/sec 4 clients 4 procs max_latency=165.722 ms XFS seems to exhibit similar latency improvements as ext2: 3.8.0-rc3: WriteX 125739 0.028 104.343 ReadX 399070 0.005 4.115 Flush 17851 25.004 131.390 Throughput 66.0024 MB/sec 4 clients 4 procs max_latency=131.406 ms 3.8.0-rc3 + patches: WriteX 123529 0.028 6.299 ReadX 392434 0.005 4.287 Flush 17549 25.120 188.687 Throughput 64.9113 MB/sec 4 clients 4 procs max_latency=188.704 ms ...and btrfs, just to round things out, also shows some latency decreases: 3.8.0-rc3: WriteX 67122 0.083 82.355 ReadX 212719 0.005 2.828 Flush 9547 47.561 147.418 Throughput 35.3391 MB/sec 4 clients 4 procs max_latency=147.433 ms 3.8.0-rc3 + patches: WriteX 64898 0.101 71.631 ReadX 206673 0.005 7.123 Flush 9190 47.963 219.034 Throughput 34.0795 MB/sec 4 clients 4 procs max_latency=219.044 ms Before this patchset, all filesystems would block, regardless of whether or not it was necessary. ext3 would wait, but still generate occasional checksum errors. The network filesystems were left to do their own thing, so they'd wait too. After this patchset, all the disk filesystems except ext3 and btrfs will wait only if the hardware requires it. ext3 (if necessary) snapshots pages instead of blocking, and btrfs provides its own bdi so the mm will never wait. Network filesystems haven't been touched, so either they provide their own wait code, or they don't block at all. The blocking behavior is back to what it was before 3.0 if you don't have a disk requiring stable page writes. This patchset has been tested on 3.8.0-rc3 on x64 with ext3, ext4, and xfs. I've spot-checked 3.8.0-rc4 and seem to be getting the same results as -rc3. [1] The alternative fixes to ext3 include fixing the locking order and page bit handling like we did for ext4 (but then why not just use ext4?), or setting PG_writeback so early that ext3 becomes extremely slow. I tried that, but the number of write()s I could initiate dropped by nearly an order of magnitude. That was a bit much even for the author of the stable page series! :) This patch: Creates a per-backing-device flag that tracks whether or not pages must be held immutable during writeout. Eventually it will be used to waive wait_for_page_writeback() if nothing requires stable pages. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Artem Bityutskiy <dedekind1@gmail.com> Cc: Joel Becker <jlbec@evilplan.org> Cc: Mark Fasheh <mfasheh@suse.com> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Eric Van Hensbergen <ericvh@gmail.com> Cc: Ron Minnich <rminnich@sandia.gov> Cc: Latchesar Ionkov <lucho@ionkov.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
869 lines
22 KiB
C
869 lines
22 KiB
C
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#include <linux/wait.h>
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#include <linux/backing-dev.h>
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#include <linux/kthread.h>
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#include <linux/freezer.h>
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#include <linux/fs.h>
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#include <linux/pagemap.h>
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#include <linux/mm.h>
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#include <linux/sched.h>
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#include <linux/module.h>
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#include <linux/writeback.h>
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#include <linux/device.h>
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#include <trace/events/writeback.h>
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static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
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struct backing_dev_info default_backing_dev_info = {
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.name = "default",
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.ra_pages = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
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.state = 0,
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.capabilities = BDI_CAP_MAP_COPY,
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};
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EXPORT_SYMBOL_GPL(default_backing_dev_info);
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struct backing_dev_info noop_backing_dev_info = {
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.name = "noop",
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.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
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};
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EXPORT_SYMBOL_GPL(noop_backing_dev_info);
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static struct class *bdi_class;
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/*
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* bdi_lock protects updates to bdi_list and bdi_pending_list, as well as
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* reader side protection for bdi_pending_list. bdi_list has RCU reader side
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* locking.
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*/
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DEFINE_SPINLOCK(bdi_lock);
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LIST_HEAD(bdi_list);
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LIST_HEAD(bdi_pending_list);
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void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2)
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{
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if (wb1 < wb2) {
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spin_lock(&wb1->list_lock);
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spin_lock_nested(&wb2->list_lock, 1);
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} else {
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spin_lock(&wb2->list_lock);
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spin_lock_nested(&wb1->list_lock, 1);
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}
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}
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#ifdef CONFIG_DEBUG_FS
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#include <linux/debugfs.h>
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#include <linux/seq_file.h>
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static struct dentry *bdi_debug_root;
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static void bdi_debug_init(void)
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{
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bdi_debug_root = debugfs_create_dir("bdi", NULL);
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}
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static int bdi_debug_stats_show(struct seq_file *m, void *v)
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{
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struct backing_dev_info *bdi = m->private;
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struct bdi_writeback *wb = &bdi->wb;
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unsigned long background_thresh;
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unsigned long dirty_thresh;
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unsigned long bdi_thresh;
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unsigned long nr_dirty, nr_io, nr_more_io;
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struct inode *inode;
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nr_dirty = nr_io = nr_more_io = 0;
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spin_lock(&wb->list_lock);
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list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
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nr_dirty++;
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list_for_each_entry(inode, &wb->b_io, i_wb_list)
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nr_io++;
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list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
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nr_more_io++;
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spin_unlock(&wb->list_lock);
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global_dirty_limits(&background_thresh, &dirty_thresh);
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bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
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#define K(x) ((x) << (PAGE_SHIFT - 10))
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seq_printf(m,
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"BdiWriteback: %10lu kB\n"
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"BdiReclaimable: %10lu kB\n"
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"BdiDirtyThresh: %10lu kB\n"
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"DirtyThresh: %10lu kB\n"
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"BackgroundThresh: %10lu kB\n"
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"BdiDirtied: %10lu kB\n"
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"BdiWritten: %10lu kB\n"
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"BdiWriteBandwidth: %10lu kBps\n"
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"b_dirty: %10lu\n"
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"b_io: %10lu\n"
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"b_more_io: %10lu\n"
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"bdi_list: %10u\n"
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"state: %10lx\n",
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(unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
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(unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
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K(bdi_thresh),
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K(dirty_thresh),
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K(background_thresh),
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(unsigned long) K(bdi_stat(bdi, BDI_DIRTIED)),
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(unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)),
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(unsigned long) K(bdi->write_bandwidth),
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nr_dirty,
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nr_io,
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nr_more_io,
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!list_empty(&bdi->bdi_list), bdi->state);
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#undef K
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return 0;
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}
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static int bdi_debug_stats_open(struct inode *inode, struct file *file)
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{
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return single_open(file, bdi_debug_stats_show, inode->i_private);
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}
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static const struct file_operations bdi_debug_stats_fops = {
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.open = bdi_debug_stats_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = single_release,
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};
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static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
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{
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bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
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bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
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bdi, &bdi_debug_stats_fops);
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}
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static void bdi_debug_unregister(struct backing_dev_info *bdi)
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{
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debugfs_remove(bdi->debug_stats);
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debugfs_remove(bdi->debug_dir);
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}
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#else
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static inline void bdi_debug_init(void)
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{
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}
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static inline void bdi_debug_register(struct backing_dev_info *bdi,
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const char *name)
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{
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}
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static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
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{
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}
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#endif
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static ssize_t read_ahead_kb_store(struct device *dev,
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struct device_attribute *attr,
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const char *buf, size_t count)
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{
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struct backing_dev_info *bdi = dev_get_drvdata(dev);
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unsigned long read_ahead_kb;
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ssize_t ret;
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ret = kstrtoul(buf, 10, &read_ahead_kb);
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if (ret < 0)
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return ret;
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bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
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return count;
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}
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#define K(pages) ((pages) << (PAGE_SHIFT - 10))
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#define BDI_SHOW(name, expr) \
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static ssize_t name##_show(struct device *dev, \
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struct device_attribute *attr, char *page) \
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{ \
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struct backing_dev_info *bdi = dev_get_drvdata(dev); \
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\
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return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \
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}
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BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
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static ssize_t min_ratio_store(struct device *dev,
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struct device_attribute *attr, const char *buf, size_t count)
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{
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struct backing_dev_info *bdi = dev_get_drvdata(dev);
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unsigned int ratio;
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ssize_t ret;
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ret = kstrtouint(buf, 10, &ratio);
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if (ret < 0)
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return ret;
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ret = bdi_set_min_ratio(bdi, ratio);
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if (!ret)
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ret = count;
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return ret;
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}
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BDI_SHOW(min_ratio, bdi->min_ratio)
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static ssize_t max_ratio_store(struct device *dev,
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struct device_attribute *attr, const char *buf, size_t count)
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{
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struct backing_dev_info *bdi = dev_get_drvdata(dev);
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unsigned int ratio;
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ssize_t ret;
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ret = kstrtouint(buf, 10, &ratio);
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if (ret < 0)
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return ret;
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ret = bdi_set_max_ratio(bdi, ratio);
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if (!ret)
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ret = count;
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return ret;
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}
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BDI_SHOW(max_ratio, bdi->max_ratio)
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static ssize_t stable_pages_required_show(struct device *dev,
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struct device_attribute *attr,
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char *page)
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{
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struct backing_dev_info *bdi = dev_get_drvdata(dev);
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return snprintf(page, PAGE_SIZE-1, "%d\n",
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bdi_cap_stable_pages_required(bdi) ? 1 : 0);
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}
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#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
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static struct device_attribute bdi_dev_attrs[] = {
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__ATTR_RW(read_ahead_kb),
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__ATTR_RW(min_ratio),
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__ATTR_RW(max_ratio),
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__ATTR_RO(stable_pages_required),
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__ATTR_NULL,
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};
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static __init int bdi_class_init(void)
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{
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bdi_class = class_create(THIS_MODULE, "bdi");
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if (IS_ERR(bdi_class))
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return PTR_ERR(bdi_class);
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bdi_class->dev_attrs = bdi_dev_attrs;
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bdi_debug_init();
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return 0;
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}
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postcore_initcall(bdi_class_init);
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static int __init default_bdi_init(void)
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{
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int err;
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err = bdi_init(&default_backing_dev_info);
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if (!err)
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bdi_register(&default_backing_dev_info, NULL, "default");
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err = bdi_init(&noop_backing_dev_info);
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return err;
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}
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subsys_initcall(default_bdi_init);
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int bdi_has_dirty_io(struct backing_dev_info *bdi)
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{
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return wb_has_dirty_io(&bdi->wb);
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}
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static void wakeup_timer_fn(unsigned long data)
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{
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struct backing_dev_info *bdi = (struct backing_dev_info *)data;
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spin_lock_bh(&bdi->wb_lock);
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if (bdi->wb.task) {
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trace_writeback_wake_thread(bdi);
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wake_up_process(bdi->wb.task);
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} else if (bdi->dev) {
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/*
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* When bdi tasks are inactive for long time, they are killed.
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* In this case we have to wake-up the forker thread which
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* should create and run the bdi thread.
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*/
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trace_writeback_wake_forker_thread(bdi);
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wake_up_process(default_backing_dev_info.wb.task);
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}
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spin_unlock_bh(&bdi->wb_lock);
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}
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/*
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* This function is used when the first inode for this bdi is marked dirty. It
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* wakes-up the corresponding bdi thread which should then take care of the
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* periodic background write-out of dirty inodes. Since the write-out would
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* starts only 'dirty_writeback_interval' centisecs from now anyway, we just
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* set up a timer which wakes the bdi thread up later.
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*
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* Note, we wouldn't bother setting up the timer, but this function is on the
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* fast-path (used by '__mark_inode_dirty()'), so we save few context switches
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* by delaying the wake-up.
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*/
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void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
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{
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unsigned long timeout;
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timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
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mod_timer(&bdi->wb.wakeup_timer, jiffies + timeout);
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}
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/*
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* Calculate the longest interval (jiffies) bdi threads are allowed to be
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* inactive.
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*/
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static unsigned long bdi_longest_inactive(void)
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{
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unsigned long interval;
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interval = msecs_to_jiffies(dirty_writeback_interval * 10);
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return max(5UL * 60 * HZ, interval);
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}
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/*
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* Clear pending bit and wakeup anybody waiting for flusher thread creation or
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* shutdown
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*/
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static void bdi_clear_pending(struct backing_dev_info *bdi)
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{
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clear_bit(BDI_pending, &bdi->state);
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smp_mb__after_clear_bit();
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wake_up_bit(&bdi->state, BDI_pending);
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}
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static int bdi_forker_thread(void *ptr)
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{
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struct bdi_writeback *me = ptr;
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current->flags |= PF_SWAPWRITE;
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set_freezable();
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/*
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* Our parent may run at a different priority, just set us to normal
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*/
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set_user_nice(current, 0);
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for (;;) {
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struct task_struct *task = NULL;
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struct backing_dev_info *bdi;
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enum {
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NO_ACTION, /* Nothing to do */
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FORK_THREAD, /* Fork bdi thread */
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KILL_THREAD, /* Kill inactive bdi thread */
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} action = NO_ACTION;
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/*
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* Temporary measure, we want to make sure we don't see
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* dirty data on the default backing_dev_info
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*/
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if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) {
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del_timer(&me->wakeup_timer);
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wb_do_writeback(me, 0);
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}
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spin_lock_bh(&bdi_lock);
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/*
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* In the following loop we are going to check whether we have
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* some work to do without any synchronization with tasks
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* waking us up to do work for them. Set the task state here
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* so that we don't miss wakeups after verifying conditions.
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*/
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set_current_state(TASK_INTERRUPTIBLE);
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list_for_each_entry(bdi, &bdi_list, bdi_list) {
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bool have_dirty_io;
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if (!bdi_cap_writeback_dirty(bdi) ||
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bdi_cap_flush_forker(bdi))
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continue;
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WARN(!test_bit(BDI_registered, &bdi->state),
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"bdi %p/%s is not registered!\n", bdi, bdi->name);
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have_dirty_io = !list_empty(&bdi->work_list) ||
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wb_has_dirty_io(&bdi->wb);
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/*
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* If the bdi has work to do, but the thread does not
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* exist - create it.
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*/
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if (!bdi->wb.task && have_dirty_io) {
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/*
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* Set the pending bit - if someone will try to
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* unregister this bdi - it'll wait on this bit.
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|
*/
|
|
set_bit(BDI_pending, &bdi->state);
|
|
action = FORK_THREAD;
|
|
break;
|
|
}
|
|
|
|
spin_lock(&bdi->wb_lock);
|
|
|
|
/*
|
|
* If there is no work to do and the bdi thread was
|
|
* inactive long enough - kill it. The wb_lock is taken
|
|
* to make sure no-one adds more work to this bdi and
|
|
* wakes the bdi thread up.
|
|
*/
|
|
if (bdi->wb.task && !have_dirty_io &&
|
|
time_after(jiffies, bdi->wb.last_active +
|
|
bdi_longest_inactive())) {
|
|
task = bdi->wb.task;
|
|
bdi->wb.task = NULL;
|
|
spin_unlock(&bdi->wb_lock);
|
|
set_bit(BDI_pending, &bdi->state);
|
|
action = KILL_THREAD;
|
|
break;
|
|
}
|
|
spin_unlock(&bdi->wb_lock);
|
|
}
|
|
spin_unlock_bh(&bdi_lock);
|
|
|
|
/* Keep working if default bdi still has things to do */
|
|
if (!list_empty(&me->bdi->work_list))
|
|
__set_current_state(TASK_RUNNING);
|
|
|
|
switch (action) {
|
|
case FORK_THREAD:
|
|
__set_current_state(TASK_RUNNING);
|
|
task = kthread_create(bdi_writeback_thread, &bdi->wb,
|
|
"flush-%s", dev_name(bdi->dev));
|
|
if (IS_ERR(task)) {
|
|
/*
|
|
* If thread creation fails, force writeout of
|
|
* the bdi from the thread. Hopefully 1024 is
|
|
* large enough for efficient IO.
|
|
*/
|
|
writeback_inodes_wb(&bdi->wb, 1024,
|
|
WB_REASON_FORKER_THREAD);
|
|
} else {
|
|
/*
|
|
* The spinlock makes sure we do not lose
|
|
* wake-ups when racing with 'bdi_queue_work()'.
|
|
* And as soon as the bdi thread is visible, we
|
|
* can start it.
|
|
*/
|
|
spin_lock_bh(&bdi->wb_lock);
|
|
bdi->wb.task = task;
|
|
spin_unlock_bh(&bdi->wb_lock);
|
|
wake_up_process(task);
|
|
}
|
|
bdi_clear_pending(bdi);
|
|
break;
|
|
|
|
case KILL_THREAD:
|
|
__set_current_state(TASK_RUNNING);
|
|
kthread_stop(task);
|
|
bdi_clear_pending(bdi);
|
|
break;
|
|
|
|
case NO_ACTION:
|
|
if (!wb_has_dirty_io(me) || !dirty_writeback_interval)
|
|
/*
|
|
* There are no dirty data. The only thing we
|
|
* should now care about is checking for
|
|
* inactive bdi threads and killing them. Thus,
|
|
* let's sleep for longer time, save energy and
|
|
* be friendly for battery-driven devices.
|
|
*/
|
|
schedule_timeout(bdi_longest_inactive());
|
|
else
|
|
schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
|
|
try_to_freeze();
|
|
break;
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Remove bdi from bdi_list, and ensure that it is no longer visible
|
|
*/
|
|
static void bdi_remove_from_list(struct backing_dev_info *bdi)
|
|
{
|
|
spin_lock_bh(&bdi_lock);
|
|
list_del_rcu(&bdi->bdi_list);
|
|
spin_unlock_bh(&bdi_lock);
|
|
|
|
synchronize_rcu_expedited();
|
|
}
|
|
|
|
int bdi_register(struct backing_dev_info *bdi, struct device *parent,
|
|
const char *fmt, ...)
|
|
{
|
|
va_list args;
|
|
struct device *dev;
|
|
|
|
if (bdi->dev) /* The driver needs to use separate queues per device */
|
|
return 0;
|
|
|
|
va_start(args, fmt);
|
|
dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
|
|
va_end(args);
|
|
if (IS_ERR(dev))
|
|
return PTR_ERR(dev);
|
|
|
|
bdi->dev = dev;
|
|
|
|
/*
|
|
* Just start the forker thread for our default backing_dev_info,
|
|
* and add other bdi's to the list. They will get a thread created
|
|
* on-demand when they need it.
|
|
*/
|
|
if (bdi_cap_flush_forker(bdi)) {
|
|
struct bdi_writeback *wb = &bdi->wb;
|
|
|
|
wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s",
|
|
dev_name(dev));
|
|
if (IS_ERR(wb->task))
|
|
return PTR_ERR(wb->task);
|
|
}
|
|
|
|
bdi_debug_register(bdi, dev_name(dev));
|
|
set_bit(BDI_registered, &bdi->state);
|
|
|
|
spin_lock_bh(&bdi_lock);
|
|
list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
|
|
spin_unlock_bh(&bdi_lock);
|
|
|
|
trace_writeback_bdi_register(bdi);
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(bdi_register);
|
|
|
|
int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
|
|
{
|
|
return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
|
|
}
|
|
EXPORT_SYMBOL(bdi_register_dev);
|
|
|
|
/*
|
|
* Remove bdi from the global list and shutdown any threads we have running
|
|
*/
|
|
static void bdi_wb_shutdown(struct backing_dev_info *bdi)
|
|
{
|
|
struct task_struct *task;
|
|
|
|
if (!bdi_cap_writeback_dirty(bdi))
|
|
return;
|
|
|
|
/*
|
|
* Make sure nobody finds us on the bdi_list anymore
|
|
*/
|
|
bdi_remove_from_list(bdi);
|
|
|
|
/*
|
|
* If setup is pending, wait for that to complete first
|
|
*/
|
|
wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
|
|
TASK_UNINTERRUPTIBLE);
|
|
|
|
/*
|
|
* Finally, kill the kernel thread. We don't need to be RCU
|
|
* safe anymore, since the bdi is gone from visibility.
|
|
*/
|
|
spin_lock_bh(&bdi->wb_lock);
|
|
task = bdi->wb.task;
|
|
bdi->wb.task = NULL;
|
|
spin_unlock_bh(&bdi->wb_lock);
|
|
|
|
if (task)
|
|
kthread_stop(task);
|
|
}
|
|
|
|
/*
|
|
* This bdi is going away now, make sure that no super_blocks point to it
|
|
*/
|
|
static void bdi_prune_sb(struct backing_dev_info *bdi)
|
|
{
|
|
struct super_block *sb;
|
|
|
|
spin_lock(&sb_lock);
|
|
list_for_each_entry(sb, &super_blocks, s_list) {
|
|
if (sb->s_bdi == bdi)
|
|
sb->s_bdi = &default_backing_dev_info;
|
|
}
|
|
spin_unlock(&sb_lock);
|
|
}
|
|
|
|
void bdi_unregister(struct backing_dev_info *bdi)
|
|
{
|
|
struct device *dev = bdi->dev;
|
|
|
|
if (dev) {
|
|
bdi_set_min_ratio(bdi, 0);
|
|
trace_writeback_bdi_unregister(bdi);
|
|
bdi_prune_sb(bdi);
|
|
del_timer_sync(&bdi->wb.wakeup_timer);
|
|
|
|
if (!bdi_cap_flush_forker(bdi))
|
|
bdi_wb_shutdown(bdi);
|
|
bdi_debug_unregister(bdi);
|
|
|
|
spin_lock_bh(&bdi->wb_lock);
|
|
bdi->dev = NULL;
|
|
spin_unlock_bh(&bdi->wb_lock);
|
|
|
|
device_unregister(dev);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(bdi_unregister);
|
|
|
|
static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
|
|
{
|
|
memset(wb, 0, sizeof(*wb));
|
|
|
|
wb->bdi = bdi;
|
|
wb->last_old_flush = jiffies;
|
|
INIT_LIST_HEAD(&wb->b_dirty);
|
|
INIT_LIST_HEAD(&wb->b_io);
|
|
INIT_LIST_HEAD(&wb->b_more_io);
|
|
spin_lock_init(&wb->list_lock);
|
|
setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi);
|
|
}
|
|
|
|
/*
|
|
* Initial write bandwidth: 100 MB/s
|
|
*/
|
|
#define INIT_BW (100 << (20 - PAGE_SHIFT))
|
|
|
|
int bdi_init(struct backing_dev_info *bdi)
|
|
{
|
|
int i, err;
|
|
|
|
bdi->dev = NULL;
|
|
|
|
bdi->min_ratio = 0;
|
|
bdi->max_ratio = 100;
|
|
bdi->max_prop_frac = FPROP_FRAC_BASE;
|
|
spin_lock_init(&bdi->wb_lock);
|
|
INIT_LIST_HEAD(&bdi->bdi_list);
|
|
INIT_LIST_HEAD(&bdi->work_list);
|
|
|
|
bdi_wb_init(&bdi->wb, bdi);
|
|
|
|
for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
|
|
err = percpu_counter_init(&bdi->bdi_stat[i], 0);
|
|
if (err)
|
|
goto err;
|
|
}
|
|
|
|
bdi->dirty_exceeded = 0;
|
|
|
|
bdi->bw_time_stamp = jiffies;
|
|
bdi->written_stamp = 0;
|
|
|
|
bdi->balanced_dirty_ratelimit = INIT_BW;
|
|
bdi->dirty_ratelimit = INIT_BW;
|
|
bdi->write_bandwidth = INIT_BW;
|
|
bdi->avg_write_bandwidth = INIT_BW;
|
|
|
|
err = fprop_local_init_percpu(&bdi->completions);
|
|
|
|
if (err) {
|
|
err:
|
|
while (i--)
|
|
percpu_counter_destroy(&bdi->bdi_stat[i]);
|
|
}
|
|
|
|
return err;
|
|
}
|
|
EXPORT_SYMBOL(bdi_init);
|
|
|
|
void bdi_destroy(struct backing_dev_info *bdi)
|
|
{
|
|
int i;
|
|
|
|
/*
|
|
* Splice our entries to the default_backing_dev_info, if this
|
|
* bdi disappears
|
|
*/
|
|
if (bdi_has_dirty_io(bdi)) {
|
|
struct bdi_writeback *dst = &default_backing_dev_info.wb;
|
|
|
|
bdi_lock_two(&bdi->wb, dst);
|
|
list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
|
|
list_splice(&bdi->wb.b_io, &dst->b_io);
|
|
list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
|
|
spin_unlock(&bdi->wb.list_lock);
|
|
spin_unlock(&dst->list_lock);
|
|
}
|
|
|
|
bdi_unregister(bdi);
|
|
|
|
/*
|
|
* If bdi_unregister() had already been called earlier, the
|
|
* wakeup_timer could still be armed because bdi_prune_sb()
|
|
* can race with the bdi_wakeup_thread_delayed() calls from
|
|
* __mark_inode_dirty().
|
|
*/
|
|
del_timer_sync(&bdi->wb.wakeup_timer);
|
|
|
|
for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
|
|
percpu_counter_destroy(&bdi->bdi_stat[i]);
|
|
|
|
fprop_local_destroy_percpu(&bdi->completions);
|
|
}
|
|
EXPORT_SYMBOL(bdi_destroy);
|
|
|
|
/*
|
|
* For use from filesystems to quickly init and register a bdi associated
|
|
* with dirty writeback
|
|
*/
|
|
int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
|
|
unsigned int cap)
|
|
{
|
|
char tmp[32];
|
|
int err;
|
|
|
|
bdi->name = name;
|
|
bdi->capabilities = cap;
|
|
err = bdi_init(bdi);
|
|
if (err)
|
|
return err;
|
|
|
|
sprintf(tmp, "%.28s%s", name, "-%d");
|
|
err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
|
|
if (err) {
|
|
bdi_destroy(bdi);
|
|
return err;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(bdi_setup_and_register);
|
|
|
|
static wait_queue_head_t congestion_wqh[2] = {
|
|
__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
|
|
__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
|
|
};
|
|
static atomic_t nr_bdi_congested[2];
|
|
|
|
void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
|
|
{
|
|
enum bdi_state bit;
|
|
wait_queue_head_t *wqh = &congestion_wqh[sync];
|
|
|
|
bit = sync ? BDI_sync_congested : BDI_async_congested;
|
|
if (test_and_clear_bit(bit, &bdi->state))
|
|
atomic_dec(&nr_bdi_congested[sync]);
|
|
smp_mb__after_clear_bit();
|
|
if (waitqueue_active(wqh))
|
|
wake_up(wqh);
|
|
}
|
|
EXPORT_SYMBOL(clear_bdi_congested);
|
|
|
|
void set_bdi_congested(struct backing_dev_info *bdi, int sync)
|
|
{
|
|
enum bdi_state bit;
|
|
|
|
bit = sync ? BDI_sync_congested : BDI_async_congested;
|
|
if (!test_and_set_bit(bit, &bdi->state))
|
|
atomic_inc(&nr_bdi_congested[sync]);
|
|
}
|
|
EXPORT_SYMBOL(set_bdi_congested);
|
|
|
|
/**
|
|
* congestion_wait - wait for a backing_dev to become uncongested
|
|
* @sync: SYNC or ASYNC IO
|
|
* @timeout: timeout in jiffies
|
|
*
|
|
* Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
|
|
* write congestion. If no backing_devs are congested then just wait for the
|
|
* next write to be completed.
|
|
*/
|
|
long congestion_wait(int sync, long timeout)
|
|
{
|
|
long ret;
|
|
unsigned long start = jiffies;
|
|
DEFINE_WAIT(wait);
|
|
wait_queue_head_t *wqh = &congestion_wqh[sync];
|
|
|
|
prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
|
|
ret = io_schedule_timeout(timeout);
|
|
finish_wait(wqh, &wait);
|
|
|
|
trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
|
|
jiffies_to_usecs(jiffies - start));
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(congestion_wait);
|
|
|
|
/**
|
|
* wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
|
|
* @zone: A zone to check if it is heavily congested
|
|
* @sync: SYNC or ASYNC IO
|
|
* @timeout: timeout in jiffies
|
|
*
|
|
* In the event of a congested backing_dev (any backing_dev) and the given
|
|
* @zone has experienced recent congestion, this waits for up to @timeout
|
|
* jiffies for either a BDI to exit congestion of the given @sync queue
|
|
* or a write to complete.
|
|
*
|
|
* In the absence of zone congestion, cond_resched() is called to yield
|
|
* the processor if necessary but otherwise does not sleep.
|
|
*
|
|
* The return value is 0 if the sleep is for the full timeout. Otherwise,
|
|
* it is the number of jiffies that were still remaining when the function
|
|
* returned. return_value == timeout implies the function did not sleep.
|
|
*/
|
|
long wait_iff_congested(struct zone *zone, int sync, long timeout)
|
|
{
|
|
long ret;
|
|
unsigned long start = jiffies;
|
|
DEFINE_WAIT(wait);
|
|
wait_queue_head_t *wqh = &congestion_wqh[sync];
|
|
|
|
/*
|
|
* If there is no congestion, or heavy congestion is not being
|
|
* encountered in the current zone, yield if necessary instead
|
|
* of sleeping on the congestion queue
|
|
*/
|
|
if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
|
|
!zone_is_reclaim_congested(zone)) {
|
|
cond_resched();
|
|
|
|
/* In case we scheduled, work out time remaining */
|
|
ret = timeout - (jiffies - start);
|
|
if (ret < 0)
|
|
ret = 0;
|
|
|
|
goto out;
|
|
}
|
|
|
|
/* Sleep until uncongested or a write happens */
|
|
prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
|
|
ret = io_schedule_timeout(timeout);
|
|
finish_wait(wqh, &wait);
|
|
|
|
out:
|
|
trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
|
|
jiffies_to_usecs(jiffies - start));
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(wait_iff_congested);
|
|
|
|
int pdflush_proc_obsolete(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp, loff_t *ppos)
|
|
{
|
|
char kbuf[] = "0\n";
|
|
|
|
if (*ppos) {
|
|
*lenp = 0;
|
|
return 0;
|
|
}
|
|
|
|
if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
|
|
return -EFAULT;
|
|
printk_once(KERN_WARNING "%s exported in /proc is scheduled for removal\n",
|
|
table->procname);
|
|
|
|
*lenp = 2;
|
|
*ppos += *lenp;
|
|
return 2;
|
|
}
|