We loop through all of the dirty block groups during commit and write
the free space cache. In order to make sure the cache is currect, we do
this while no other writers are allowed in the commit.
If a large number of block groups are dirty, this can introduce long
stalls during the final stages of the commit, which can block new procs
trying to change the filesystem.
This commit changes the block group cache writeout to take appropriate
locks and allow it to run earlier in the commit. We'll still have to
redo some of the block groups, but it means we can get most of the work
out of the way without blocking the entire FS.
Signed-off-by: Chris Mason <clm@fb.com>
As we delete large extents, we end up doing huge amounts of COW in order
to delete the corresponding crcs. This adds accounting so that we keep
track of that space and flushing of delayed refs so that we don't build
up too much delayed crc work.
This helps limit the delayed work that must be done at commit time and
tries to avoid ENOSPC aborts because the crcs eat all the global
reserves.
Signed-off-by: Chris Mason <clm@fb.com>
When we are deleting large files with large extents, we are building up
a huge set of delayed refs for processing. Truncate isn't checking
often enough to see if we need to back off and process those, or let
a commit proceed.
The end result is long stalls after the rm, and very long commit times.
During the commits, other processes back up waiting to start new
transactions and we get into trouble.
Signed-off-by: Chris Mason <clm@fb.com>
Pull btrfs fixes from Chris Mason:
"Most of these are fixing extent reservation accounting, or corners
with tree writeback during commit.
Josef's set does add a test, which isn't strictly a fix, but it'll
keep us from making this same mistake again"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
Btrfs: fix outstanding_extents accounting in DIO
Btrfs: add sanity test for outstanding_extents accounting
Btrfs: just free dummy extent buffers
Btrfs: account merges/splits properly
Btrfs: prepare block group cache before writing
Btrfs: fix ASSERT(list_empty(&cur_trans->dirty_bgs_list)
Btrfs: account for the correct number of extents for delalloc reservations
Btrfs: fix merge delalloc logic
Btrfs: fix comp_oper to get right order
Btrfs: catch transaction abortion after waiting for it
btrfs: fix sizeof format specifier in btrfs_check_super_valid()
Writing the block group cache will modify the extent tree quite a bit because it
truncates the old space cache and pre-allocates new stuff. To try and cut down
on the churn lets do the setup dance first, then later on hopefully we can avoid
looping with newly dirtied roots. Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Dave could hit this assert consistently running btrfs/078. This is because
when we update the block groups we could truncate the free space, which would
try to delete the csums for that range and dirty the csum root. For this to
happen we have to have already written out the csum root so it's kind of hard to
hit this case. This patch fixes this by changing the logic to only write the
dirty block groups if the dirty_cowonly_roots list is empty. This will get us
the same effect as before since we add the extent root last, and will cover the
case that we dirty some other root again but not the extent root. Thanks,
Reported-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
This problem is uncovered by a test case: http://patchwork.ozlabs.org/patch/244297.
Fsync() can report success when it actually doesn't. When we
have several threads running fsync() at the same tiem and in one fsync() we
get a transaction abortion due to some problems(in the test case it's disk
failures), and other fsync()s may return successfully which makes userspace
programs think that data is now safely flushed into disk.
It's because that after fsyncs() fail btrfs_sync_log() due to disk failures,
they get to try btrfs_commit_transaction() where it finds that there is
already a transaction being committed, and they'll just call wait_for_commit()
and return. Note that we actually check "trans->aborted" in btrfs_end_transaction,
but it's likely that the error message is still not yet throwed out and only after
wait_for_commit() we're sure whether the transaction is committed successfully.
This add the necessary check and it now passes the test.
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Chris Mason <clm@fb.com>
Pull btrfs fixes from Chris Mason:
"Outside of misc fixes, Filipe has a few fsync corners and we're
pulling in one more of Josef's fixes from production use here"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
Btrfs:__add_inode_ref: out of bounds memory read when looking for extended ref.
Btrfs: fix data loss in the fast fsync path
Btrfs: remove extra run_delayed_refs in update_cowonly_root
Btrfs: incremental send, don't rename a directory too soon
btrfs: fix lost return value due to variable shadowing
Btrfs: do not ignore errors from btrfs_lookup_xattr in do_setxattr
Btrfs: fix off-by-one logic error in btrfs_realloc_node
Btrfs: add missing inode update when punching hole
Btrfs: abort the transaction if we fail to update the free space cache inode
Btrfs: fix fsync race leading to ordered extent memory leaks
Clean the opencoded variant, cond_resched_lock also checks the lock for
contention so it might help in some cases that were not covered by
simple need_resched().
Signed-off-by: David Sterba <dsterba@suse.cz>
Pull btrfs updates from Chris Mason:
"This pull is mostly cleanups and fixes:
- The raid5/6 cleanups from Zhao Lei fixup some long standing warts
in the code and add improvements on top of the scrubbing support
from 3.19.
- Josef has round one of our ENOSPC fixes coming from large btrfs
clusters here at FB.
- Dave Sterba continues a long series of cleanups (thanks Dave), and
Filipe continues hammering on corner cases in fsync and others
This all was held up a little trying to track down a use-after-free in
btrfs raid5/6. It's not clear yet if this is just made easier to
trigger with this pull or if its a new bug from the raid5/6 cleanups.
Dave Sterba is the only one to trigger it so far, but he has a
consistent way to reproduce, so we'll get it nailed shortly"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs: (68 commits)
Btrfs: don't remove extents and xattrs when logging new names
Btrfs: fix fsync data loss after adding hard link to inode
Btrfs: fix BUG_ON in btrfs_orphan_add() when delete unused block group
Btrfs: account for large extents with enospc
Btrfs: don't set and clear delalloc for O_DIRECT writes
Btrfs: only adjust outstanding_extents when we do a short write
btrfs: Fix out-of-space bug
Btrfs: scrub, fix sleep in atomic context
Btrfs: fix scheduler warning when syncing log
Btrfs: Remove unnecessary placeholder in btrfs_err_code
btrfs: cleanup init for list in free-space-cache
btrfs: delete chunk allocation attemp when setting block group ro
btrfs: clear bio reference after submit_one_bio()
Btrfs: fix scrub race leading to use-after-free
Btrfs: add missing cleanup on sysfs init failure
Btrfs: fix race between transaction commit and empty block group removal
btrfs: add more checks to btrfs_read_sys_array
btrfs: cleanup, rename a few variables in btrfs_read_sys_array
btrfs: add checks for sys_chunk_array sizes
btrfs: more superblock checks, lower bounds on devices and sectorsize/nodesize
...
There are some op tables that can be easily made const, similarly the
sysfs feature and raid tables. This is motivated by PaX CONSTIFY plugin.
Signed-off-by: David Sterba <dsterba@suse.cz>
Btrfs will report NO_SPACE when we create and remove files for several times,
and we can't write to filesystem until mount it again.
Steps to reproduce:
1: Create a single-dev btrfs fs with default option
2: Write a file into it to take up most fs space
3: Delete above file
4: Wait about 100s to let chunk removed
5: goto 2
Script is like following:
#!/bin/bash
# Recommend 1.2G space, too large disk will make test slow
DEV="/dev/sda16"
MNT="/mnt/tmp"
dev_size="$(lsblk -bn -o SIZE "$DEV")" || exit 2
file_size_m=$((dev_size * 75 / 100 / 1024 / 1024))
echo "Loop write ${file_size_m}M file on $((dev_size / 1024 / 1024))M dev"
for ((i = 0; i < 10; i++)); do umount "$MNT" 2>/dev/null; done
echo "mkfs $DEV"
mkfs.btrfs -f "$DEV" >/dev/null || exit 2
echo "mount $DEV $MNT"
mount "$DEV" "$MNT" || exit 2
for ((loop_i = 0; loop_i < 20; loop_i++)); do
echo
echo "loop $loop_i"
echo "dd file..."
cmd=(dd if=/dev/zero of="$MNT"/file0 bs=1M count="$file_size_m")
"${cmd[@]}" 2>/dev/null || {
# NO_SPACE error triggered
echo "dd failed: ${cmd[*]}"
exit 1
}
echo "rm file..."
rm -f "$MNT"/file0 || exit 2
for ((i = 0; i < 10; i++)); do
df "$MNT" | tail -1
sleep 10
done
done
Reason:
It is triggered by commit: 47ab2a6c68
which is used to remove empty block groups automatically, but the
reason is not in that patch. Code before works well because btrfs
don't need to create and delete chunks so many times with high
complexity.
Above bug is caused by many reason, any of them can trigger it.
Reason1:
When we remove some continuous chunks but leave other chunks after,
these disk space should be used by chunk-recreating, but in current
code, only first create will successed.
Fixed by Forrest Liu <forrestl@synology.com> in:
Btrfs: fix find_free_dev_extent() malfunction in case device tree has hole
Reason2:
contains_pending_extent() return wrong value in calculation.
Fixed by Forrest Liu <forrestl@synology.com> in:
Btrfs: fix find_free_dev_extent() malfunction in case device tree has hole
Reason3:
btrfs_check_data_free_space() try to commit transaction and retry
allocating chunk when the first allocating failed, but space_info->full
is set in first allocating, and prevent second allocating in retry.
Fixed in this patch by clear space_info->full in commit transaction.
Tested for severial times by above script.
Changelog v3->v4:
use light weight int instead of atomic_t to record have_remove_bgs in
transaction, suggested by:
Josef Bacik <jbacik@fb.com>
Changelog v2->v3:
v2 fixed the bug by adding more commit-transaction, but we
only need to reclaim space when we are really have no space for
new chunk, noticed by:
Filipe David Manana <fdmanana@gmail.com>
Actually, our code already have this type of commit-and-retry,
we only need to make it working with removed-bgs.
v3 fixed the bug with above way.
Changelog v1->v2:
v1 will introduce a new bug when delete and create chunk in same disk
space in same transaction, noticed by:
Filipe David Manana <fdmanana@gmail.com>
V2 fix this bug by commit transaction after remove block grops.
Reported-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Suggested-by: Filipe David Manana <fdmanana@gmail.com>
Suggested-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
Currently any time we try to update the block groups on disk we will walk _all_
block groups and check for the ->dirty flag to see if it is set. This function
can get called several times during a commit. So if you have several terabytes
of data you will be a very sad panda as we will loop through _all_ of the block
groups several times, which makes the commit take a while which slows down the
rest of the file system operations.
This patch introduces a dirty list for the block groups that we get added to
when we dirty the block group for the first time. Then we simply update any
block groups that have been dirtied since the last time we called
btrfs_write_dirty_block_groups. This allows us to clean up how we write the
free space cache out so it is much cleaner. Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
I've been overloading root->dirty_list to keep track of dirty roots and which
roots need to have their commit roots switched at transaction commit time. This
could cause us to lose an update to the root which could corrupt the file
system. To fix this use a state bit to know if the root is dirty, and if it
isn't set we go ahead and move the root to the dirty list. This way if we
re-dirty the root after adding it to the switch_commit list we make sure to
update it. This also makes it so that the extent root is always the last root
on the dirty list to try and keep the amount of churn down at this point in the
commit. Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
Fs_info->pending_changes is never cleared since the original code uses
cmpxchg(&fs_info->pending_changes, 0, 0), which will only clear it if
pending_changes is already 0.
This will cause a lot of problem when mount it with inode_cache mount
option.
If the btrfs is mounted as inode_cache, pending_changes will always be
1, even when the fs is frozen.
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>
Liu Bo pointed out that my previous fix would lose the generation update in the
scenario I described. It is actually much worse than that, we could lose the
entire extent if we lose power right after the transaction commits. Consider
the following
write extent 0-4k
log extent in log tree
commit transaction
< power fail happens here
ordered extent completes
We would lose the 0-4k extent because it hasn't updated the actual fs tree, and
the transaction commit will reset the log so it isn't replayed. If we lose
power before the transaction commit we are save, otherwise we are not.
Fix this by keeping track of all extents we logged in this transaction. Then
when we go to commit the transaction make sure we wait for all of those ordered
extents to complete before proceeding. This will make sure that if we lose
power after the transaction commit we still have our data. This also fixes the
problem of the improperly updated extent generation. Thanks,
cc: stable@vger.kernel.org
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
Right now the only caller of find_first_extent_bit() that is interested
in caching extent states (transaction or log commit), never gets an extent
state cached. This is because find_first_extent_bit() only caches states
that have at least one of the flags EXTENT_IOBITS or EXTENT_BOUNDARY, and
the transaction/log commit caller always passes a tree that doesn't have
ever extent states with any of those flags (they can only have one of the
following flags: EXTENT_DIRTY, EXTENT_NEW or EXTENT_NEED_WAIT).
This change together with the following one in the patch series (titled
"Btrfs: avoid returning -ENOMEM in convert_extent_bit() too early") will
help reduce significantly the chances of calls to convert_extent_bit()
fail with -ENOMEM when called from the transaction/log commit code.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
When committing a transaction or a log, we look for btree extents that
need to be durably persisted by searching for ranges in a io tree that
have some bits set (EXTENT_DIRTY or EXTENT_NEW). We then attempt to clear
those bits and set the EXTENT_NEED_WAIT bit, with calls to the function
convert_extent_bit, and then start writeback for the extents.
That function however can return an error (at the moment only -ENOMEM
is possible, specially when it does GFP_ATOMIC allocation requests
through alloc_extent_state_atomic) - that means the ranges didn't got
the EXTENT_NEED_WAIT bit set (or at least not for the whole range),
which in turn means a call to btrfs_wait_marked_extents() won't find
those ranges for which we started writeback, causing a transaction
commit or a log commit to persist a new superblock without waiting
for the writeback of extents in that range to finish first.
Therefore if a crash happens after persisting the new superblock and
before writeback finishes, we have a superblock pointing to roots that
weren't fully persisted or roots that point to nodes or leafs that weren't
fully persisted, causing all sorts of unexpected/bad behaviour as we endup
reading garbage from disk or the content of some node/leaf from a past
generation that got cowed or deleted and is no longer valid (for this later
case we end up getting error messages like "parent transid verify failed on
X wanted Y found Z" when reading btree nodes/leafs from disk).
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
In some contexts, like in sysfs handlers, we don't want to trigger a
transaction commit. It's a heavy operation, we don't know what external
locks may be taken. Instead, make it possible to finish the operation
through sync syscall or SYNC_FS ioctl.
Signed-off-by: David Sterba <dsterba@suse.cz>
The pending mount option(s) now share namespace and bits with the normal
options, and the existing one for (inode_cache) is unset unconditionally
at each transaction commit.
Introduce a separate namespace for pending changes and enhance the
descriptions of the intended change to use separate bits for each
action.
Signed-off-by: David Sterba <dsterba@suse.cz>
There are some actions that modify global filesystem state but cannot be
performed at the time of request, but later at the transaction commit
time when the filesystem is in a known state.
For example enabling new incompat features on-the-fly or issuing
transaction commit from unsafe contexts (sysfs handlers).
Signed-off-by: David Sterba <dsterba@suse.cz>
We check whether transid is already committed via last_trans_committed and
then search through trans_list for pending transactions. If
last_trans_committed is updated by btrfs_commit_transaction after we check
it (there is no locking), we will fail to find the committed transaction
and return EINVAL to the caller. This has been observed occasionally by
ceph-osd (which uses this ioctl heavily).
Fix by rechecking whether the provided transid <= last_trans_committed
after the search fails, and if so return 0.
Signed-off-by: Sage Weil <sage@redhat.com>
Signed-off-by: Chris Mason <clm@fb.com>
While we have a transaction ongoing, the VM might decide at any time
to call btree_inode->i_mapping->a_ops->writepages(), which will start
writeback of dirty pages belonging to btree nodes/leafs. This call
might return an error or the writeback might finish with an error
before we attempt to commit the running transaction. If this happens,
we might have no way of knowing that such error happened when we are
committing the transaction - because the pages might no longer be
marked dirty nor tagged for writeback (if a subsequent modification
to the extent buffer didn't happen before the transaction commit) which
makes filemap_fdata[write|wait]_range unable to find such pages (even
if they're marked with SetPageError).
So if this happens we must abort the transaction, otherwise we commit
a super block with btree roots that point to btree nodes/leafs whose
content on disk is invalid - either garbage or the content of some
node/leaf from a past generation that got cowed or deleted and is no
longer valid (for this later case we end up getting error messages like
"parent transid verify failed on 10826481664 wanted 25748 found 29562"
when reading btree nodes/leafs from disk).
Note that setting and checking AS_EIO/AS_ENOSPC in the btree inode's
i_mapping would not be enough because we need to distinguish between
log tree extents (not fatal) vs non-log tree extents (fatal) and
because the next call to filemap_fdatawait_range() will catch and clear
such errors in the mapping - and that call might be from a log sync and
not from a transaction commit, which means we would not know about the
error at transaction commit time. Also, checking for the eb flag
EXTENT_BUFFER_IOERR at transaction commit time isn't done and would
not be completely reliable, as the eb might be removed from memory and
read back when trying to get it, which clears that flag right before
reading the eb's pages from disk, making us not know about the previous
write error.
Using the new 3 flags for the btree inode also makes us achieve the
goal of AS_EIO/AS_ENOSPC when writepages() returns success, started
writeback for all dirty pages and before filemap_fdatawait_range() is
called, the writeback for all dirty pages had already finished with
errors - because we were not using AS_EIO/AS_ENOSPC,
filemap_fdatawait_range() would return success, as it could not know
that writeback errors happened (the pages were no longer tagged for
writeback).
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
There are the branch hints that obviously depend on the data being
processed, the CPU predictor will do better job according to the actual
load. It also does not make sense to use the hints in slow paths that do
a lot of other operations like locking, waiting or IO.
Signed-off-by: David Sterba <dsterba@suse.cz>
device->bytes_used will be changed when allocating a new chunk, and
disk_total_size will be changed if resizing is successful.
Meanwhile, the on-disk super blocks of the previous transaction
might not be updated. Considering the consistency of the metadata
in the previous transaction, We should use the size in the previous
transaction to check if the super block is beyond the boundary
of the device.
Though it is not big problem because we don't use it now, but anyway
it is better that we make it be consistent with the common metadata,
maybe we will use it in the future.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
total_size will be changed when resizing a device, and disk_total_size
will be changed if resizing is successful. Meanwhile, the on-disk super
blocks of the previous transaction might not be updated. Considering
the consistency of the metadata in the previous transaction, We should
use the size in the previous transaction to check if the super block is
beyond the boundary of the device. Fix it.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
The nodesize and leafsize were never of different values. Unify the
usage and make nodesize the one. Cleanup the redundant checks and
helpers.
Shaves a few bytes from .text:
text data bss dec hex filename
852418 24560 23112 900090 dbbfa btrfs.ko.before
851074 24584 23112 898770 db6d2 btrfs.ko.after
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>
Truncates and renames are often used to replace old versions of a file
with new versions. Applications often expect this to be an atomic
replacement, even if they haven't done anything to make sure the new
version is fully on disk.
Btrfs has strict flushing in place to make sure that renaming over an
old file with a new file will fully flush out the new file before
allowing the transaction commit with the rename to complete.
This ordering means the commit code needs to be able to lock file pages,
and there are a few paths in the filesystem where we will try to end a
transaction with the page lock held. It's rare, but these things can
deadlock.
This patch removes the ordered flushes and switches to a best effort
filemap_flush like ext4 uses. It's not perfect, but it should fix the
deadlocks.
Signed-off-by: Chris Mason <clm@fb.com>
When starting a transaction just assert that current->journal_info
doesn't contain a send transaction stub, since send isn't supposed
to start transactions and when it finishes (either successfully or
not) it's supposed to set current->journal_info to NULL.
This is motivated by the change titled:
Btrfs: fix crash when starting transaction
Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Chris Mason <clm@fb.com>
fcebe456 cut and pasted some code to a later point
in create_pending_snapshot(), but didn't switch
to the appropriate error handling for this stage
of the function.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Chris Mason <clm@fb.com>
Delayed extent operations are triggered during transaction commits.
The goal is to queue up a healthly batch of changes to the extent
allocation tree and run through them in bulk.
This farms them off to async helper threads. The goal is to have the
bulk of the delayed operations being done in the background, but this is
also important to limit our stack footprint.
Signed-off-by: Chris Mason <clm@fb.com>
Currently qgroups account for space by intercepting delayed ref updates to fs
trees. It does this by adding sequence numbers to delayed ref updates so that
it can figure out how the tree looked before the update so we can adjust the
counters properly. The problem with this is that it does not allow delayed refs
to be merged, so if you say are defragging an extent with 5k snapshots pointing
to it we will thrash the delayed ref lock because we need to go back and
manually merge these things together. Instead we want to process quota changes
when we know they are going to happen, like when we first allocate an extent, we
free a reference for an extent, we add new references etc. This patch
accomplishes this by only adding qgroup operations for real ref changes. We
only modify the sequence number when we need to lookup roots for bytenrs, this
reduces the amount of churn on the sequence number and allows us to merge
delayed refs as we add them most of the time. This patch encompasses a bunch of
architectural changes
1) qgroup ref operations: instead of tracking qgroup operations through the
delayed refs we simply add new ref operations whenever we notice that we need to
when we've modified the refs themselves.
2) tree mod seq: we no longer have this separation of major/minor counters.
this makes the sequence number stuff much more sane and we can remove some
locking that was needed to protect the counter.
3) delayed ref seq: we now read the tree mod seq number and use that as our
sequence. This means each new delayed ref doesn't have it's own unique sequence
number, rather whenever we go to lookup backrefs we inc the sequence number so
we can make sure to keep any new operations from screwing up our world view at
that given point. This allows us to merge delayed refs during runtime.
With all of these changes the delayed ref stuff is a little saner and the qgroup
accounting stuff no longer goes negative in some cases like it was before.
Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
Lets try this again. We can deadlock the box if we send on a box and try to
write onto the same fs with the app that is trying to listen to the send pipe.
This is because the writer could get stuck waiting for a transaction commit
which is being blocked by the send. So fix this by making sure looking at the
commit roots is always going to be consistent. We do this by keeping track of
which roots need to have their commit roots swapped during commit, and then
taking the commit_root_sem and swapping them all at once. Then make sure we
take a read lock on the commit_root_sem in cases where we search the commit root
to make sure we're always looking at a consistent view of the commit roots.
Previously we had problems with this because we would swap a fs tree commit root
and then swap the extent tree commit root independently which would cause the
backref walking code to screw up sometimes. With this patch we no longer
deadlock and pass all the weird send/receive corner cases. Thanks,
Reportedy-by: Hugo Mills <hugo@carfax.org.uk>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
So I have an awful exercise script that will run snapshot, balance and
send/receive in parallel. This sometimes would crash spectacularly and when it
came back up the fs would be completely hosed. Turns out this is because of a
bad interaction of balance and send/receive. Send will hold onto its entire
path for the whole send, but its blocks could get relocated out from underneath
it, and because it doesn't old tree locks theres nothing to keep this from
happening. So it will go to read in a slot with an old transid, and we could
have re-allocated this block for something else and it could have a completely
different transid. But because we think it is invalid we clear uptodate and
re-read in the block. If we do this before we actually write out the new block
we could write back stale data to the fs, and boom we're screwed.
Now we definitely need to fix this disconnect between send and balance, but we
really really need to not allow ourselves to accidently read in stale data over
new data. So make sure we check if the extent buffer is not under io before
clearing uptodate, this will kick back EIO to the caller instead of reading in
stale data and keep us from corrupting the fs. Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
Zach found this deadlock that would happen like this
btrfs_end_transaction <- reduce trans->use_count to 0
btrfs_run_delayed_refs
btrfs_cow_block
find_free_extent
btrfs_start_transaction <- increase trans->use_count to 1
allocate chunk
btrfs_end_transaction <- decrease trans->use_count to 0
btrfs_run_delayed_refs
lock tree block we are cowing above ^^
We need to only decrease trans->use_count if it is above 1, otherwise leave it
alone. This will make nested trans be the only ones who decrease their added
ref, and will let us get rid of the trans->use_count++ hack if we have to commit
the transaction. Thanks,
cc: stable@vger.kernel.org
Reported-by: Zach Brown <zab@redhat.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Tested-by: Zach Brown <zab@redhat.com>
Signed-off-by: Chris Mason <clm@fb.com>
We needn't flush all delalloc inodes when we doesn't get s_umount lock,
or we would make the tasks wait for a long time.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Chris Mason
Josef Bacik
Linus Torvalds
Liu Bo
David Sterba
Zhao Lei
Qu Wenruo
Filipe Manana
Sage Weil
Miao Xie
Filipe Manana
Eric Sandeen