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Qu Wenruo a94d1d0cb3 btrfs: Flush before reflinking any extent to prevent NOCOW write falling back to COW without data reservation 
[BUG]
The following script can cause unexpected fsync failure:

  #!/bin/bash

  dev=/dev/test/test
  mnt=/mnt/btrfs

  mkfs.btrfs -f $dev -b 512M > /dev/null
  mount $dev $mnt -o nospace_cache

  # Prealloc one extent
  xfs_io -f -c "falloc 8k 64m" $mnt/file1
  # Fill the remaining data space
  xfs_io -f -c "pwrite 0 -b 4k 512M" $mnt/padding
  sync

  # Write into the prealloc extent
  xfs_io -c "pwrite 1m 16m" $mnt/file1

  # Reflink then fsync, fsync would fail due to ENOSPC
  xfs_io -c "reflink $mnt/file1 8k 0 4k" -c "fsync" $mnt/file1
  umount $dev

The fsync fails with ENOSPC, and the last page of the buffered write is
lost.

[CAUSE]
This is caused by:
- Btrfs' back reference only has extent level granularity
  So write into shared extent must be COWed even only part of the extent
  is shared.

So for above script we have:
- fallocate
  Create a preallocated extent where we can do NOCOW write.

- fill all the remaining data and unallocated space

- buffered write into preallocated space
  As we have not enough space available for data and the extent is not
  shared (yet) we fall into NOCOW mode.

- reflink
  Now part of the large preallocated extent is shared, later write
  into that extent must be COWed.

- fsync triggers writeback
  But now the extent is shared and therefore we must fallback into COW
  mode, which fails with ENOSPC since there's not enough space to
  allocate data extents.

[WORKAROUND]
The workaround is to ensure any buffered write in the related extents
(not just the reflink source range) get flushed before reflink/dedupe,
so that NOCOW writes succeed that happened before reflinking succeed.

The workaround is expensive, we could do it better by only flushing
NOCOW range, but that needs extra accounting for NOCOW range.
For now, fix the possible data loss first.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2019-07-01 13:35:00 +02:00
..
9p treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 188 2019-05-30 11:29:21 -07:00
adfs treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
affs treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
afs AFS fixes 2019-06-28 08:34:12 +08:00
autofs treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 83 2019-05-24 17:37:52 +02:00
befs treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
bfs treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
btrfs btrfs: Flush before reflinking any extent to prevent NOCOW write falling back to COW without data reservation 2019-07-01 13:35:00 +02:00
cachefiles treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
ceph ceph: fix ceph_mdsc_build_path to not stop on first component 2019-06-27 18:27:36 +02:00
cifs SPDX update for 5.2-rc6 2019-06-21 09:58:42 -07:00
coda treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
configfs SPDX update for 5.2-rc3, round 1 2019-05-31 08:34:32 -07:00
cramfs treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
crypto treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
debugfs treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
devpts treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 83 2019-05-24 17:37:52 +02:00
dlm treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 398 2019-06-05 17:37:12 +02:00
ecryptfs treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 333 2019-06-05 17:37:06 +02:00
efivarfs treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
efs treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
exportfs treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
ext2 treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
ext4 Bug fixes (including a regression fix) for ext4. 2019-05-25 15:03:12 -07:00
f2fs treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
fat treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 282 2019-06-05 17:36:37 +02:00
freevxfs treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
fscache treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
fuse Revert "fuse: require /dev/fuse reads to have enough buffer capacity" 2019-06-11 13:35:22 +02:00
gfs2 Fix rounding error in gfs2_iomap_page_prepare 2019-06-14 17:27:12 -10:00
hfs treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
hfsplus treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
hostfs This pull request contains the following changes for UML: 2019-05-12 17:52:13 -04:00
hpfs treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
hugetlbfs treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
isofs treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 142 2019-05-30 11:25:17 -07:00
jbd2 treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
jffs2 treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
jfs treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156 2019-05-30 11:26:35 -07:00
kernfs treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 428 2019-06-05 17:37:16 +02:00
lockd Revert "lockd: Show pid of lockd for remote locks" 2019-05-31 09:43:26 -04:00
minix treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
nfs NFS/flexfiles: Use the correct TCP timeout for flexfiles I/O 2019-06-28 11:48:52 -04:00
nfs_common treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
nfsd treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 1 2019-05-21 11:28:39 +02:00
nilfs2 treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
nls treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
notify fanotify: update connector fsid cache on add mark 2019-06-19 15:53:58 +02:00
ntfs treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 97 2019-05-24 17:37:53 +02:00
ocfs2 fs/ocfs2: fix race in ocfs2_dentry_attach_lock() 2019-06-13 17:34:56 -10:00
omfs treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 209 2019-05-30 11:29:53 -07:00
openpromfs treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
orangefs treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
overlayfs SPDX update for 5.2-rc6 2019-06-21 09:58:42 -07:00
proc fs/proc/array.c: allow reporting eip/esp for all coredumping threads 2019-06-29 16:43:44 +08:00
pstore SPDX update for 5.2-rc4 2019-06-08 12:52:42 -07:00
qnx4 treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
qnx6 treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
quota quota: fix a problem about transfer quota 2019-06-19 15:25:41 +02:00
ramfs treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
reiserfs treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
romfs treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
squashfs treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 499 2019-06-19 17:09:53 +02:00
sysfs treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
sysv treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
tracefs treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
ubifs treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 336 2019-06-05 17:37:07 +02:00
udf treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
ufs treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
unicode treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 294 2019-06-05 17:36:38 +02:00
xfs block: return from __bio_try_merge_page if merging occured in the same page 2019-06-17 09:33:02 -06:00
aio.c signal: remove the wrong signal_pending() check in restore_user_sigmask() 2019-06-29 16:43:45 +08:00
anon_inodes.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
attr.c
bad_inode.c
binfmt_aout.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
binfmt_elf_fdpic.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
binfmt_elf.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
binfmt_em86.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
binfmt_flat.c fs/binfmt_flat.c: make load_flat_shared_library() work 2019-06-29 16:43:45 +08:00
binfmt_misc.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
binfmt_script.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
block_dev.c block: Don't revalidate bdev of hidden gendisk 2019-05-27 07:35:02 -06:00
buffer.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
char_dev.c chardev: update comment based on the code 2019-04-02 17:49:58 +02:00
compat_binfmt_elf.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 193 2019-05-30 11:29:21 -07:00
compat_ioctl.c
compat.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
coredump.c
d_path.c
dax.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 288 2019-06-05 17:36:37 +02:00
dcache.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
dcookies.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
direct-io.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
drop_caches.c fs/drop_caches.c: avoid softlockups in drop_pagecache_sb() 2019-02-01 15:46:24 -08:00
eventfd.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
eventpoll.c signal: remove the wrong signal_pending() check in restore_user_sigmask() 2019-06-29 16:43:45 +08:00
exec.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
fcntl.c fs: mark expected switch fall-throughs 2019-04-08 18:21:02 -05:00
fhandle.c
file_table.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
file.c io_uring-2019-03-06 2019-03-08 14:48:40 -08:00
filesystems.c vfs: Implement a filesystem superblock creation/configuration context 2019-02-28 03:29:26 -05:00
fs_context.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
fs_parser.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
fs_pin.c
fs_struct.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
fs_types.c fs: common implementation of file type 2019-01-21 17:48:13 +01:00
fs-writeback.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
fsopen.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
inode.c mm: fix page cache convergence regression 2019-05-31 13:52:41 -04:00
internal.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
io_uring.c Merge branch 'akpm' (patches from Andrew) 2019-06-29 17:11:01 +08:00
ioctl.c Remove 'type' argument from access_ok() function 2019-01-03 18:57:57 -08:00
iomap.c block: return from __bio_try_merge_page if merging occured in the same page 2019-06-17 09:33:02 -06:00
Kconfig treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Kconfig.binfmt treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
libfs.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
locks.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
Makefile Add as a feature case-insensitive directories (the casefold feature) 2019-05-07 21:12:44 -07:00
mbcache.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
mount.h saner handling of temporary namespaces 2019-01-30 17:44:07 -05:00
mpage.c block: remove the i argument to bio_for_each_segment_all 2019-04-30 09:26:13 -06:00
namei.c Clean up fscrypt's dcache revalidation support, and other 2019-05-07 21:28:04 -07:00
namespace.c fs/namespace: fix unprivileged mount propagation 2019-06-17 17:36:09 -04:00
no-block.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
nsfs.c nsfs: unobfuscate 2019-04-09 19:20:57 -04:00
open.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
pipe.c Merge branch 'page-refs' (page ref overflow) 2019-04-14 15:09:40 -07:00
pnode.c fs/namespace: fix unprivileged mount propagation 2019-06-17 17:36:09 -04:00
pnode.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 209 2019-05-30 11:29:53 -07:00
posix_acl.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
proc_namespace.c
read_write.c vfs: pass ppos=NULL to .read()/.write() of FMODE_STREAM files 2019-05-06 17:46:52 +03:00
readdir.c Remove 'type' argument from access_ok() function 2019-01-03 18:57:57 -08:00
select.c signal: remove the wrong signal_pending() check in restore_user_sigmask() 2019-06-29 16:43:45 +08:00
seq_file.c fs: mark expected switch fall-throughs 2019-04-08 18:21:02 -05:00
signalfd.c fs: mark expected switch fall-throughs 2019-04-08 18:21:02 -05:00
splice.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
stack.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
stat.c fs: move generic stat response attr handling to vfs_getattr_nosec 2019-02-01 01:55:45 -05:00
statfs.c vfs: add vfs_get_fsid() helper 2019-02-07 16:38:35 +01:00
super.c [fix] get rid of checking for absent device name in vfs_get_tree() 2019-04-28 21:34:21 -04:00
sync.c fs/sync.c: sync_file_range(2) may use WB_SYNC_ALL writeback 2019-05-14 09:47:50 -07:00
timerfd.c y2038: syscalls: rename y2038 compat syscalls 2019-02-07 00:13:27 +01:00
userfaultfd.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 499 2019-06-19 17:09:53 +02:00
utimes.c y2038: syscalls: rename y2038 compat syscalls 2019-02-07 00:13:27 +01:00
xattr.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00