linux-stable/fs
Filipe Manana d96b34248c btrfs: make send work with concurrent block group relocation
We don't allow send and balance/relocation to run in parallel in order
to prevent send failing or silently producing some bad stream. This is
because while send is using an extent (specially metadata) or about to
read a metadata extent and expecting it belongs to a specific parent
node, relocation can run, the transaction used for the relocation is
committed and the extent gets reallocated while send is still using the
extent, so it ends up with a different content than expected. This can
result in just failing to read a metadata extent due to failure of the
validation checks (parent transid, level, etc), failure to find a
backreference for a data extent, and other unexpected failures. Besides
reallocation, there's also a similar problem of an extent getting
discarded when it's unpinned after the transaction used for block group
relocation is committed.

The restriction between balance and send was added in commit 9e967495e0
("Btrfs: prevent send failures and crashes due to concurrent relocation"),
kernel 5.3, while the more general restriction between send and relocation
was added in commit 1cea5cf0e6 ("btrfs: ensure relocation never runs
while we have send operations running"), kernel 5.14.

Both send and relocation can be very long running operations. Relocation
because it has to do a lot of IO and expensive backreference lookups in
case there are many snapshots, and send due to read IO when operating on
very large trees. This makes it inconvenient for users and tools to deal
with scheduling both operations.

For zoned filesystem we also have automatic block group relocation, so
send can fail with -EAGAIN when users least expect it or send can end up
delaying the block group relocation for too long. In the future we might
also get the automatic block group relocation for non zoned filesystems.

This change makes it possible for send and relocation to run in parallel.
This is achieved the following way:

1) For all tree searches, send acquires a read lock on the commit root
   semaphore;

2) After each tree search, and before releasing the commit root semaphore,
   the leaf is cloned and placed in the search path (struct btrfs_path);

3) After releasing the commit root semaphore, the changed_cb() callback
   is invoked, which operates on the leaf and writes commands to the pipe
   (or file in case send/receive is not used with a pipe). It's important
   here to not hold a lock on the commit root semaphore, because if we did
   we could deadlock when sending and receiving to the same filesystem
   using a pipe - the send task blocks on the pipe because it's full, the
   receive task, which is the only consumer of the pipe, triggers a
   transaction commit when attempting to create a subvolume or reserve
   space for a write operation for example, but the transaction commit
   blocks trying to write lock the commit root semaphore, resulting in a
   deadlock;

4) Before moving to the next key, or advancing to the next change in case
   of an incremental send, check if a transaction used for relocation was
   committed (or is about to finish its commit). If so, release the search
   path(s) and restart the search, to where we were before, so that we
   don't operate on stale extent buffers. The search restarts are always
   possible because both the send and parent roots are RO, and no one can
   add, remove of update keys (change their offset) in RO trees - the
   only exception is deduplication, but that is still not allowed to run
   in parallel with send;

5) Periodically check if there is contention on the commit root semaphore,
   which means there is a transaction commit trying to write lock it, and
   release the semaphore and reschedule if there is contention, so as to
   avoid causing any significant delays to transaction commits.

This leaves some room for optimizations for send to have less path
releases and re searching the trees when there's relocation running, but
for now it's kept simple as it performs quite well (on very large trees
with resulting send streams in the order of a few hundred gigabytes).

Test case btrfs/187, from fstests, stresses relocation, send and
deduplication attempting to run in parallel, but without verifying if send
succeeds and if it produces correct streams. A new test case will be added
that exercises relocation happening in parallel with send and then checks
that send succeeds and the resulting streams are correct.

A final note is that for now this still leaves the mutual exclusion
between send operations and deduplication on files belonging to a root
used by send operations. A solution for that will be slightly more complex
but it will eventually be built on top of this change.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2022-01-07 14:18:23 +01:00
..
9p netfs, 9p, afs, ceph: Use folios 2021-11-10 21:16:56 +00:00
adfs mm: require ->set_page_dirty to be explicitly wired up 2021-06-29 10:53:48 -07:00
affs affs: use bdev_nr_sectors instead of open coding it 2021-10-18 14:43:22 -06:00
afs afs: Fix mmap 2021-12-16 09:10:13 -08:00
autofs autofs: fix wait name hash calculation in autofs_wait() 2021-10-20 21:09:02 -04:00
befs isystem: ship and use stdarg.h 2021-08-19 09:02:55 +09:00
bfs mm: require ->set_page_dirty to be explicitly wired up 2021-06-29 10:53:48 -07:00
btrfs btrfs: make send work with concurrent block group relocation 2022-01-07 14:18:23 +01:00
cachefiles for-5.16/ki_complete-2021-10-29 2021-11-01 10:17:11 -07:00
ceph ceph: fix up non-directory creation in SGID directories 2021-12-01 17:08:27 +01:00
cifs cifs: sanitize multiple delimiters in prepath 2021-12-17 19:16:49 -06:00
coda coda: bump module version to 7.2 2021-11-09 10:02:51 -08:00
configfs configfs: fix a race in configfs_lookup() 2021-08-25 07:58:49 +02:00
cramfs cramfs: use bdev_nr_bytes instead of open coding it 2021-10-18 14:43:22 -06:00
crypto fscrypt: improve a few comments 2021-10-25 19:11:50 -07:00
debugfs debugfs: debugfs_create_file_size(): use IS_ERR to check for error 2021-09-21 09:09:06 +02:00
devpts
dlm fs: dlm: avoid comms shutdown delay in release_lockspace 2021-09-01 11:29:14 -05:00
ecryptfs mm: require ->set_page_dirty to be explicitly wired up 2021-06-29 10:53:48 -07:00
efivarfs
efs
erofs erofs: fix deadlock when shrink erofs slab 2021-11-23 14:58:16 +08:00
exfat exfat: fix incorrect loading of i_blocks for large files 2021-11-01 07:49:21 +09:00
exportfs
ext2 ext2: fix sleeping in atomic bugs on error 2021-09-22 13:05:23 +02:00
ext4 Only bug fixes and cleanups for ext4 this merge window. Of note are 2021-11-10 17:05:37 -08:00
f2fs Update to zstd-1.4.10 2021-11-13 15:32:30 -08:00
fat for-5.16/inode-sync-2021-10-29 2021-11-01 10:25:27 -07:00
freevxfs
fscache fscache: Remove an unused static variable 2021-10-04 22:13:12 +01:00
fuse fuse: release pipe buf after last use 2021-11-25 14:05:18 +01:00
gfs2 gfs2: gfs2_create_inode rework 2021-12-02 12:41:10 +01:00
hfs Merge branch 'akpm' (patches from Andrew) 2021-11-09 10:11:53 -08:00
hfsplus Merge branch 'akpm' (patches from Andrew) 2021-11-09 10:11:53 -08:00
hostfs hostfs: support splice_write 2021-08-26 22:28:02 +02:00
hpfs treewide: Replace open-coded flex arrays in unions 2021-10-18 12:28:53 -07:00
hugetlbfs mm,hugetlb: remove mlock ulimit for SHM_HUGETLB 2021-11-09 10:02:48 -08:00
iomap iomap: iomap_read_inline_data cleanup 2021-11-24 10:15:47 -08:00
isofs isofs: Fix out of bound access for corrupted isofs image 2021-10-19 12:51:02 +02:00
jbd2 jbd2: add sparse annotations for add_transaction_credits() 2021-08-30 23:36:50 -04:00
jffs2 vfs: add rcu argument to ->get_acl() callback 2021-08-18 22:08:24 +02:00
jfs Just one JFS patch 2021-11-03 09:23:25 -07:00
kernfs Merge 5.15-rc6 into driver-core-next 2021-10-18 09:43:37 +02:00
ksmbd ksmbd: disable SMB2_GLOBAL_CAP_ENCRYPTION for SMB 3.1.1 2021-12-17 19:19:45 -06:00
lockd A slow cycle for nfsd: mainly cleanup, including Neil's patch dropping 2021-11-10 16:45:54 -08:00
minix mm: require ->set_page_dirty to be explicitly wired up 2021-06-29 10:53:48 -07:00
netfs netfs: fix parameter of cleanup() 2021-12-07 15:47:09 +00:00
nfs NFS client bugfixes for Linux 5.16 2021-11-27 10:33:55 -08:00
nfs_common nfs: Fix kerneldoc warning shown up by W=1 2021-10-04 22:02:17 +01:00
nfsd NFSD: Fix READDIR buffer overflow 2021-12-18 17:11:06 -05:00
nilfs2 Merge branch 'akpm' (patches from Andrew) 2021-11-09 10:11:53 -08:00
nls
notify fanotify: Allow users to request FAN_FS_ERROR events 2021-10-27 12:53:45 +02:00
ntfs fs: ntfs: Limit NTFS_RW to page sizes smaller than 64k 2021-11-27 14:34:41 -08:00
ntfs3 gfs2: Fix mmap + page fault deadlocks 2021-11-02 12:25:03 -07:00
ocfs2 Merge branch 'exit-cleanups-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2021-11-10 16:15:54 -08:00
omfs mm: require ->set_page_dirty to be explicitly wired up 2021-06-29 10:53:48 -07:00
openpromfs
orangefs orangefs: three fixes from other folks... 2021-11-09 10:34:06 -08:00
overlayfs overlayfs update for 5.16 2021-11-09 10:51:12 -08:00
proc proc/vmcore: fix clearing user buffer by properly using clear_user() 2021-11-20 10:35:55 -08:00
pstore pstore/blk: Use "%lu" to format unsigned long 2021-11-21 09:44:19 -08:00
qnx4 qnx4: work around gcc false positive warning bug 2021-09-21 08:36:48 -07:00
qnx6
quota \n 2021-11-06 16:40:48 -07:00
ramfs Merge branch 'akpm' (patches from Andrew) 2021-11-09 10:11:53 -08:00
reiserfs \n 2021-11-06 16:40:48 -07:00
romfs
smbfs_common cifs: Fix crash on unload of cifs_arc4.ko 2021-12-07 22:38:03 -06:00
squashfs lib: zstd: Add kernel-specific API 2021-11-08 16:55:21 -08:00
sysfs fs/sysfs/dir.c: replace S_IRWXU|S_IRUGO|S_IXUGO with 0755 sysfs_create_dir_ns() 2021-10-05 16:35:05 +02:00
sysv sysv: use BUILD_BUG_ON instead of runtime check 2021-11-09 10:02:52 -08:00
tracefs tracefs: Set all files to the same group ownership as the mount option 2021-12-08 08:06:40 -05:00
ubifs fscrypt: remove fscrypt_operations::max_namelen 2021-09-20 19:32:33 -07:00
udf udf: Fix crash after seekdir 2021-11-09 12:53:58 +01:00
ufs isystem: ship and use stdarg.h 2021-08-19 09:02:55 +09:00
unicode
vboxsf vboxfs: fix broken legacy mount signature checking 2021-09-27 11:26:21 -07:00
verity fs-verity: fix signed integer overflow with i_size near S64_MAX 2021-09-22 10:56:34 -07:00
xfs xfs: remove all COW fork extents when remounting readonly 2021-12-07 10:17:29 -08:00
zonefs zonefs: add MODULE_ALIAS_FS 2021-12-17 16:56:35 +09:00
aio.c aio: Fix incorrect usage of eventfd_signal_allowed() 2021-12-09 10:52:55 -08:00
anon_inodes.c fs: add anon_inode_getfile_secure() similar to anon_inode_getfd_secure() 2021-09-19 22:35:37 -04:00
attr.c fs: handle circular mappings correctly 2021-11-17 09:26:09 +01:00
bad_inode.c vfs: add rcu argument to ->get_acl() callback 2021-08-18 22:08:24 +02:00
binfmt_aout.c binfmt: a.out: Fix bogus semicolon 2021-09-05 10:15:05 -07:00
binfmt_elf.c Merge branch 'akpm' (patches from Andrew) 2021-11-09 10:11:53 -08:00
binfmt_elf_fdpic.c coredump: Limit coredumps to a single thread group 2021-10-08 12:06:02 -05:00
binfmt_flat.c binfmt: remove in-tree usage of MAP_EXECUTABLE 2021-06-29 10:53:50 -07:00
binfmt_misc.c
binfmt_script.c
buffer.c fs: simplify init_page_buffers 2021-10-18 14:43:22 -06:00
char_dev.c
compat_binfmt_elf.c
coredump.c coredump: Limit coredumps to a single thread group 2021-10-08 12:06:02 -05:00
d_path.c d_path: fix Kernel doc validator complaining 2021-11-06 13:30:32 -07:00
dax.c New code for 5.15: 2021-08-31 11:13:35 -07:00
dcache.c
direct-io.c fs: get rid of the res2 iocb->ki_complete argument 2021-10-25 10:36:24 -06:00
drop_caches.c fs: drop_caches: fix skipping over shadow cache inodes 2021-09-03 09:58:10 -07:00
eventfd.c eventfd: Export eventfd_wake_count to modules 2021-09-06 07:20:56 -04:00
eventpoll.c ARM development updates for 5.15: 2021-09-09 13:25:49 -07:00
exec.c Merge branch 'exit-cleanups-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2021-11-10 16:15:54 -08:00
fcntl.c Merge branch 'akpm' (patches from Andrew) 2021-09-03 10:08:28 -07:00
fhandle.c
file.c fget: clarify and improve __fget_files() implementation 2021-12-13 10:55:30 -08:00
file_table.c
filesystems.c fs: simplify get_filesystem_list / get_all_fs_names 2021-08-23 01:25:40 -04:00
fs-writeback.c Various hardening fixes and cleanups for 5.16-rc1 2021-11-01 17:29:10 -07:00
fs_context.c memcg: charge fs_context and legacy_fs_context 2021-09-03 09:58:12 -07:00
fs_parser.c namei: Standardize callers of filename_lookup() 2021-09-07 16:07:47 -04:00
fs_pin.c
fs_struct.c
fs_types.c
fsopen.c
init.c
inode.c fs: Remove FS_THP_SUPPORT 2021-11-17 10:36:35 -05:00
internal.h Merge branch 'akpm' (patches from Andrew) 2021-11-09 10:11:53 -08:00
io-wq.c io-wq: drop wqe lock before creating new worker 2021-12-13 09:04:01 -07:00
io-wq.h io_uring: optimise INIT_WQ_LIST 2021-10-19 05:49:54 -06:00
io_uring.c io_uring: zero iocb->ki_pos for stream file types 2021-12-22 20:34:32 -07:00
ioctl.c New code for 5.15: 2021-08-31 11:06:32 -07:00
Kconfig 4 cifs/smb3 fixes, one for DFS reconnect, and one to begin creating common headers for server and client and the other two to rename the cifs_common directory to smbfs_common to be more consistent ie change use of the name cifs to smb which is more accurate 2021-09-12 10:10:21 -07:00
Kconfig.binfmt binfmt: remove support for em86 (alpha only) 2021-07-25 22:33:03 -07:00
kernel_read_file.c vfs: check fd has read access in kernel_read_file_from_fd() 2021-10-18 20:22:03 -10:00
libfs.c libfs: Support RENAME_EXCHANGE in simple_rename() 2021-11-03 15:43:08 +01:00
locks.c locks: remove changelog comments 2021-10-19 14:11:39 -04:00
Makefile 4 cifs/smb3 fixes, one for DFS reconnect, and one to begin creating common headers for server and client and the other two to rename the cifs_common directory to smbfs_common to be more consistent ie change use of the name cifs to smb which is more accurate 2021-09-12 10:10:21 -07:00
mbcache.c
mount.h
mpage.c
namei.c File locking changes for v5.16 2021-11-01 09:06:53 -07:00
namespace.c fs/mount_setattr: always cleanup mount_kattr 2021-12-30 15:12:13 -08:00
no-block.c
nsfs.c
open.c Merge branch 'akpm' (patches from Andrew) 2021-11-06 14:08:17 -07:00
pipe.c Revert "mm/gup: remove try_get_page(), call try_get_compound_head() directly" 2021-09-07 11:03:45 -07:00
pnode.c
pnode.h
posix_acl.c fs/posix_acl.c: avoid -Wempty-body warning 2021-11-06 13:30:32 -07:00
proc_namespace.c
read_write.c fs: remove leftover comments from mandatory locking removal 2021-10-26 12:20:50 -04:00
readdir.c
remap_range.c fs: remove mandatory file locking support 2021-08-23 06:15:36 -04:00
select.c Revert "memcg: enable accounting for pollfd and select bits arrays" 2021-09-07 11:26:23 -07:00
seq_file.c seq_file: move seq_escape() to a header 2021-11-09 10:02:52 -08:00
signalfd.c signalfd: use wake_up_pollfree() 2021-12-09 10:49:56 -08:00
splice.c
stack.c
stat.c fs: add generic helper for filling statx attribute flags 2021-08-17 11:47:43 +02:00
statfs.c
super.c fs: explicitly unregister per-superblock BDIs 2021-11-06 13:30:34 -07:00
sync.c block: simplify the block device syncing code 2021-10-22 08:36:55 -06:00
timerfd.c timerfd: Provide timerfd_resume() 2021-08-10 17:57:22 +02:00
userfaultfd.c userfaultfd: fix a race between writeprotect and exit_mmap() 2021-10-18 20:22:02 -10:00
utimes.c
xattr.c