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  1. 15 Oct, 2019 1 commit
    • Qu Wenruo's avatar
      btrfs: qgroup: Always free PREALLOC META reserve in btrfs_delalloc_release_extents() · 8702ba93
      Qu Wenruo authored 
      [Background]
Btrfs qgroup uses two types of reserved space for METADATA space,
PERTRANS and PREALLOC.

PERTRANS is metadata space reserved for each transaction started by
btrfs_start_transaction().
While PREALLOC is for delalloc, where we reserve space before joining a
transaction, and finally it will be converted to PERTRANS after the
writeback is done.

[Inconsistency]
However there is inconsistency in how we handle PREALLOC metadata space.

The most obvious one is:
In btrfs_buffered_write():
	btrfs_delalloc_release_extents(BTRFS_I(inode), reserve_bytes, true);

We always free qgroup PREALLOC meta space.

While in btrfs_truncate_block():
	btrfs_delalloc_release_extents(BTRFS_I(inode), blocksize, (ret != 0));

We only free qgroup PREALLOC meta space when something went wrong.

[The Correct Behavior]
The correct behavior should be the one in btrfs_buffered_write(), we
should always free PREALLOC metadata space.

The reason is, the btrfs_delalloc_* mechanism works by:
- Reserve metadata first, even it's not necessary
  In btrfs_delalloc_reserve_metadata()

- Free the unused metadata space
  Normally in:
  btrfs_delalloc_release_extents()
  |- btrfs_inode_rsv_release()
     Here we do calculation on whether we should release or not.

E.g. for 64K buffered write, the metadata rsv works like:

/* The first page */
reserve_meta:	num_bytes=calc_inode_reservations()
free_meta:	num_bytes=0
total:		num_bytes=calc_inode_reservations()
/* The first page caused one outstanding extent, thus needs metadata
   rsv */

/* The 2nd page */
reserve_meta:	num_bytes=calc_inode_reservations()
free_meta:	num_bytes=calc_inode_reservations()
total:		not changed
/* The 2nd page doesn't cause new outstanding extent, needs no new meta
   rsv, so we free what we have reserved */

/* The 3rd~16th pages */
reserve_meta:	num_bytes=calc_inode_reservations()
free_meta:	num_bytes=calc_inode_reservations()
total:		not changed (still space for one outstanding extent)

This means, if btrfs_delalloc_release_extents() determines to free some
space, then those space should be freed NOW.
So for qgroup, we should call btrfs_qgroup_free_meta_prealloc() other
than btrfs_qgroup_convert_reserved_meta().

The good news is:
- The callers are not that hot
  The hottest caller is in btrfs_buffered_write(), which is already
  fixed by commit 336a8bb8 ("btrfs: Fix wrong
  btrfs_delalloc_release_extents parameter"). Thus it's not that
  easy to cause false EDQUOT.

- The trans commit in advance for qgroup would hide the bug
  Since commit f5fef459 ("btrfs: qgroup: Make qgroup async transaction
  commit more aggressive"), when btrfs qgroup metadata free space is slow,
  it will try to commit transaction and free the wrongly converted
  PERTRANS space, so it's not that easy to hit such bug.

[FIX]
So to fix the problem, remove the @qgroup_free parameter for
btrfs_delalloc_release_extents(), and always pass true to
btrfs_inode_rsv_release().
Reported-by: default avatarFilipe Manana <fdmanana@suse.com>
Fixes: 43b18595 ("btrfs: qgroup: Use separate meta reservation type for delalloc")
CC: stable@vger.kernel.org # 4.19+
Reviewed-by: default avatarFilipe Manana <fdmanana@suse.com>
Signed-off-by: default avatarQu Wenruo <wqu@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
      8702ba93
  3. 01 Oct, 2019 1 commit
    • Josef Bacik's avatar
      btrfs: allocate new inode in NOFS context · 11a19a90
      Josef Bacik authored 
      A user reported a lockdep splat

 ======================================================
 WARNING: possible circular locking dependency detected
 5.2.11-gentoo #2 Not tainted
 ------------------------------------------------------
 kswapd0/711 is trying to acquire lock:
 000000007777a663 (sb_internal){.+.+}, at: start_transaction+0x3a8/0x500

but task is already holding lock:
 000000000ba86300 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x30

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (fs_reclaim){+.+.}:
 kmem_cache_alloc+0x1f/0x1c0
 btrfs_alloc_inode+0x1f/0x260
 alloc_inode+0x16/0xa0
 new_inode+0xe/0xb0
 btrfs_new_inode+0x70/0x610
 btrfs_symlink+0xd0/0x420
 vfs_symlink+0x9c/0x100
 do_symlinkat+0x66/0xe0
 do_syscall_64+0x55/0x1c0
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 (sb_internal){.+.+}:
 __sb_start_write+0xf6/0x150
 start_transaction+0x3a8/0x500
 btrfs_commit_inode_delayed_inode+0x59/0x110
 btrfs_evict_inode+0x19e/0x4c0
 evict+0xbc/0x1f0
 inode_lru_isolate+0x113/0x190
 __list_lru_walk_one.isra.4+0x5c/0x100
 list_lru_walk_one+0x32/0x50
 prune_icache_sb+0x36/0x80
 super_cache_scan+0x14a/0x1d0
 do_shrink_slab+0x131/0x320
 shrink_node+0xf7/0x380
 balance_pgdat+0x2d5/0x640
 kswapd+0x2ba/0x5e0
 kthread+0x147/0x160
 ret_from_fork+0x24/0x30

other info that might help us debug this:

 Possible unsafe locking scenario:

 CPU0 CPU1
 ---- ----
 lock(fs_reclaim);
 lock(sb_internal);
 lock(fs_reclaim);
 lock(sb_internal);
*** DEADLOCK ***

 3 locks held by kswapd0/711:
 #0: 000000000ba86300 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x30
 #1: 000000004a5100f8 (shrinker_rwsem){++++}, at: shrink_node+0x9a/0x380
 #2: 00000000f956fa46 (&type->s_umount_key#30){++++}, at: super_cache_scan+0x35/0x1d0

stack backtrace:
 CPU: 7 PID: 711 Comm: kswapd0 Not tainted 5.2.11-gentoo #2
 Hardware name: Dell Inc. Precision Tower 3620/0MWYPT, BIOS 2.4.2 09/29/2017
 Call Trace:
 dump_stack+0x85/0xc7
 print_circular_bug.cold.40+0x1d9/0x235
 __lock_acquire+0x18b1/0x1f00
 lock_acquire+0xa6/0x170
 ? start_transaction+0x3a8/0x500
 __sb_start_write+0xf6/0x150
 ? start_transaction+0x3a8/0x500
 start_transaction+0x3a8/0x500
 btrfs_commit_inode_delayed_inode+0x59/0x110
 btrfs_evict_inode+0x19e/0x4c0
 ? var_wake_function+0x20/0x20
 evict+0xbc/0x1f0
 inode_lru_isolate+0x113/0x190
 ? discard_new_inode+0xc0/0xc0
 __list_lru_walk_one.isra.4+0x5c/0x100
 ? discard_new_inode+0xc0/0xc0
 list_lru_walk_one+0x32/0x50
 prune_icache_sb+0x36/0x80
 super_cache_scan+0x14a/0x1d0
 do_shrink_slab+0x131/0x320
 shrink_node+0xf7/0x380
 balance_pgdat+0x2d5/0x640
 kswapd+0x2ba/0x5e0
 ? __wake_up_common_lock+0x90/0x90
 kthread+0x147/0x160
 ? balance_pgdat+0x640/0x640
 ? __kthread_create_on_node+0x160/0x160
 ret_from_fork+0x24/0x30

This is because btrfs_new_inode() calls new_inode() under the
transaction.  We could probably move the new_inode() outside of this but
for now just wrap it in memalloc_nofs_save().
Reported-by: default avatarZdenek Sojka <zsojka@seznam.cz>
Fixes: 712e36c5 ("btrfs: use GFP_KERNEL in btrfs_alloc_inode")
CC: stable@vger.kernel.org # 4.16+
Reviewed-by: default avatarFilipe Manana <fdmanana@suse.com>
Signed-off-by: default avatarJosef Bacik <josef@toxicpanda.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
      11a19a90
  5. 09 Sep, 2019 18 commits
  7. 17 Jul, 2019 1 commit
    • Qu Wenruo's avatar
      btrfs: inode: Don't compress if NODATASUM or NODATACOW set · 42c16da6
      Qu Wenruo authored 
      As btrfs(5) specified:

	Note
	If nodatacow or nodatasum are enabled, compression is disabled.

If NODATASUM or NODATACOW set, we should not compress the extent.

Normally NODATACOW is detected properly in run_delalloc_range() so
compression won't happen for NODATACOW.

However for NODATASUM we don't have any check, and it can cause
compressed extent without csum pretty easily, just by:
  mkfs.btrfs -f $dev
  mount $dev $mnt -o nodatasum
  touch $mnt/foobar
  mount -o remount,datasum,compress $mnt
  xfs_io -f -c "pwrite 0 128K" $mnt/foobar

And in fact, we have a bug report about corrupted compressed extent
without proper data checksum so even RAID1 can't recover the corruption.
(https://bugzilla.kernel.org/show_bug.cgi?id=199707)

Running compression without proper checksum could cause more damage when
corruption happens, as compressed data could make the whole extent
unreadable, so there is no need to allow compression for
NODATACSUM.

The fix will refactor the inode compression check into two parts:

- inode_can_compress()
  As the hard requirement, checked at btrfs_run_delalloc_range(), so no
  compression will happen for NODATASUM inode at all.

- inode_need_compress()
  As the soft requirement, checked at btrfs_run_delalloc_range() and
  compress_file_range().
Reported-by: default avatarJames Harvey <jamespharvey20@gmail.com>
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: default avatarQu Wenruo <wqu@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
      42c16da6
  9. 04 Jul, 2019 1 commit
  11. 02 Jul, 2019 2 commits
    • Josef Bacik's avatar
      btrfs: run delayed iput at unlink time · 63611e73
      Josef Bacik authored 
      We have been seeing issues in production where a cleaner script will end
up unlinking a bunch of files that have pending iputs.  This means they
will get their final iput's run at btrfs-cleaner time and thus are not
throttled, which impacts the workload.

Since we are unlinking these files we can just drop the delayed iput at
unlink time.  We are already holding a reference to the inode so this
will not be the final iput and thus is completely safe to do at this
point.  Doing this means we are more likely to be doing the final iput
at unlink time, and thus will get the IO charged to the caller and get
throttled appropriately without affecting the main workload.
Reviewed-by: default avatarNikolay Borisov <nborisov@suse.com>
Signed-off-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
      63611e73
    • Nikolay Borisov's avatar
      btrfs: Use btrfs_get_io_geometry appropriately · 89b798ad
      Nikolay Borisov authored 
      Presently btrfs_map_block is used not only to do everything necessary to
map a bio to the underlying allocation profile but it's also used to
identify how much data could be written based on btrfs' stripe logic
without actually submitting anything. This is achieved by passing NULL
for 'bbio_ret' parameter.

This patch refactors all callers that require just the mapping length
by switching them to using btrfs_io_geometry instead of calling
btrfs_map_block with a special NULL value for 'bbio_ret'. No functional
change.
Signed-off-by: default avatarNikolay Borisov <nborisov@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
      89b798ad
  13. 01 Jul, 2019 4 commits
  15. 28 May, 2019 1 commit
    • Filipe Manana's avatar
      Btrfs: fix wrong ctime and mtime of a directory after log replay · 5338e43a
      Filipe Manana authored 
      When replaying a log that contains a new file or directory name that needs
to be added to its parent directory, we end up updating the mtime and the
ctime of the parent directory to the current time after we have set their
values to the correct ones (set at fsync time), efectivelly losing them.

Sample reproducer:

  $ mkfs.btrfs -f /dev/sdb
  $ mount /dev/sdb /mnt

  $ mkdir /mnt/dir
  $ touch /mnt/dir/file

  # fsync of the directory is optional, not needed
  $ xfs_io -c fsync /mnt/dir
  $ xfs_io -c fsync /mnt/dir/file

  $ stat -c %Y /mnt/dir
  1557856079

  <power failure>

  $ sleep 3
  $ mount /dev/sdb /mnt
  $ stat -c %Y /mnt/dir
  1557856082

    --> should have been 1557856079, the mtime is updated to the current
        time when replaying the log

Fix this by not updating the mtime and ctime to the current time at
btrfs_add_link() when we are replaying a log tree.

This could be triggered by my recent fsync fuzz tester for fstests, for
which an fstests patch exists titled "fstests: generic, fsync fuzz tester
with fsstress".

Fixes: e02119d5 ("Btrfs: Add a write ahead tree log to optimize synchronous operations")
CC: stable@vger.kernel.org # 4.4+
Reviewed-by: default avatarNikolay Borisov <nborisov@suse.com>
Signed-off-by: default avatarFilipe Manana <fdmanana@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
      5338e43a
  17. 02 May, 2019 9 commits
  19. 01 May, 2019 1 commit
    • Linus Torvalds's avatar
      gcc-9: don't warn about uninitialized btrfs extent_type variable · 7e74e235
      Linus Torvalds authored 
      The 'extent_type' variable does seem to be reliably initialized, but
it's _very_ non-obvious, since there's a "goto next" case that jumps
over the normal initialization.  That will then always trigger the
"start >= extent_end" test, which will end up never falling through to
the use of that variable.

But the code is certainly not obvious, and the compiler warning looks
reasonable.  Make 'extent_type' an int, and initialize it to an invalid
negative value, which seems to be the common pattern in other places.
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      7e74e235
  21. 30 Apr, 2019 1 commit
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