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Currently the extent map shrinker is run synchronously for kswapd tasks
that end up calling the fs shrinker (fs/super.c:super_cache_scan()).
This has some disadvantages and for some heavy workloads with memory
pressure it can cause some delays and stalls that make a machine
unresponsive for some periods. This happens because:
1) We can have several kswapd tasks on machines with multiple NUMA zones,
and running the extent map shrinker concurrently can cause high
contention on some spin locks, namely the spin locks that protect
the radix tree that tracks roots, the per root xarray that tracks
open inodes and the list of delayed iputs. This not only delays the
shrinker but also causes high CPU consumption and makes the task
running the shrinker monopolize a core, resulting in the symptoms
of an unresponsive system. This was noted in previous commits such as
commit ae1e766f623f ("btrfs: only run the extent map shrinker from
kswapd tasks");
2) The extent map shrinker's iteration over inodes can often be slow, even
after changing the data structure that tracks open inodes for a root
from a red black tree (up to kernel 6.10) to an xarray (kernel 6.10+).
The transition to the xarray while it made things a bit faster, it's
still somewhat slow - for example in a test scenario with 10000 inodes
that have no extent maps loaded, the extent map shrinker took between
5ms to 8ms, using a release, non-debug kernel. Iterating over the
extent maps of an inode can also be slow if have an inode with many
thousands of extent maps, since we use a red black tree to track and
search extent maps. So having the extent map shrinker run synchronously
adds extra delay for other things a kswapd task does.
So make the extent map shrinker run asynchronously as a job for the
system unbounded workqueue, just like what we do for data and metadata
space reclaim jobs.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Move the common code to remove an extent map from its inode's tree into a
helper function and use it, reducing duplicated code.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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When crawling btree, if an eb cache miss occurs, we change to use the eb
read lock and release all previous locks (including the parent lock) to
reduce lock contention.
If an eb cache miss occurs in a leaf and needs to execute IO, before this
change we released locks only from level 2 and up and we read a leaf's
content from disk while holding a lock on its parent (level 1), causing
the unnecessary lock contention on the parent, after this change we
release locks from level 1 and up, but we lock level 0, and read leaf's
content from disk.
Because we have prepared the check parameters and the read lock of eb we
hold, we can ensure that no race will occur during the check and cause
unexpected errors.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Robbie Ko <robbieko@synology.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The compression heuristic pass does not need a level, so we can drop the
parameter.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Cascaded removal of fs_info that is not needed in several functions.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The function got split in commit 6ab6ebb76042d3 ("btrfs: split
alloc_log_tree()") and since then transaction parameter has been unused.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The only caller passes NULL, we can drop the parameter. This is since
the new mount option parser done in 3bb17a25bcb09a ("btrfs: add get_tree
callback for new mount API").
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Since the new mount option parser in commit ad21f15b0f79 ("btrfs:
switch to the new mount API") we don't pass the options like that
anymore.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The parameter was added in 8ff8466d29efc2 ("btrfs: support subpage for
extent buffer page release") for page but hasn't been used since, so we
can drop it.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The mask parameter used for allocations got unified to GFP_NOFS and
removed from relevant functions in 1d1268004430 ("btrfs: drop gfp from
parameter extent state helpers").
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The parameter duplicates what can be effectively obtained from
wc->refs[level - 1] and this is what's actually used inside. Added in
commit 2b73c7e761c4 ("btrfs: unify logic to decide if we need to walk
down into a node during snapshot delete").
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The parameter 'from' has never been used since commit b8d8e1fd570a
("btrfs: introduce btrfs_write_check()"), this is for buffered write.
Direct io write needs it so it was probably an interface thing, but we
can drop it.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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btrfs_encoded_read_regular_fill_pages()
The file_offset parameter used to be passed to encoded read struct but
was removed in commit b665affe93d8 ("btrfs: remove unused members from
struct btrfs_encoded_read_private").
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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We don't need offset for inline extents, they always start from 0.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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We don't need the inode pointer to read inline extent, it's all
accessible from the path pointer.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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We don't need the user passed parameter, rescan is a filesystem
operation so fs_info is sufficient.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The LZO compression has only one level, we don't need to pass the
parameter.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The caller replace_path() runs under transaction but we don't need it in
btrfs_qgroup_add_swapped_blocks().
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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We don't need fs_info here, everything is reachable from qgroup.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The parameter map used to be passed to scrub_extent() until
e02ee89baa66c4 ("btrfs: scrub: switch scrub_simple_mirror() to
scrub_stripe infrastructure"), where the scrub implementation was
completely reworked.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The parameter is unused and we can reach sctx from scrub stripe if
needed.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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None of the ref iteration callbacks needs the index parameter (this is
for the directory item iteration), so we can drop it.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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None of the ref iteration callbacks needs the num parameter (this is for
the directory item iteration), so we can drop it.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The parameter is unused and we can get it from space info if needed.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The parameter is not used, we can also reach it from the space info if
needed in the future.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The ctx parameter is not used, we can drop it.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The path parameter was used for our own locking, that got converted to
rwsem eventually. Last usage in ac5887c8e013d6 ("btrfs: locking: remove
all the blocking helpers").
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Make sure we got the right timer struct for the zstd workspace reclaim
work.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The function btrfs_set_range_writeback() was originally a callback for
metadata and data, to mark a range with writeback flag.
Then it was converted into a common function call for both metadata and
data.
From the very beginning, the function had been only called on a full page,
later converted to handle range inside a page.
But it never needed to handle multiple pages, and since commit
8189197425e7 ("btrfs: refactor __extent_writepage_io() to do
sector-by-sector submission") the function was only called on a
sector-by-sector basis.
This makes the function unnecessary, and can be converted to a simple
btrfs_folio_set_writeback() call instead.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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When trying to flush qgroups in order to release space we run delayed
iputs in order to release space from recently deleted files (their link
counted reached zero), and then we start delalloc and wait for any
existing ordered extents to complete.
However there's a time window here where we end up not doing the final
iput on a deleted file which could release necessary space:
1) An unlink operation starts;
2) During the unlink, or right before it completes, delalloc is flushed
and an ordered extent is created;
3) When the ordered extent is created, the inode's ref count is
incremented (with igrab() at alloc_ordered_extent());
4) When the unlink finishes it doesn't drop the last reference on the
inode and so it doesn't trigger inode eviction to delete all of
the inode's items in its root and drop all references on its data
extents;
5) Another task enters try_flush_qgroup() to try to release space,
it runs all delayed iputs, but there's no delayed iput yet for that
deleted file because the ordered extent hasn't completed yet;
6) Then at try_flush_qgroup() we wait for the ordered extent to complete
and that results in adding a delayed iput at btrfs_put_ordered_extent()
when called from btrfs_finish_one_ordered();
7) Adding the delayed iput results in waking the cleaner kthread if it's
not running already. However it may take some time for it to be
scheduled, or it may be running but busy running auto defrag, dropping
deleted snapshots or doing other work, so by the time we return from
try_flush_qgroup() the space for deleted file isn't released.
Improve on this by running delayed iputs only after flushing delalloc
and waiting for ordered extent completion.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Performing the initial extent sector read on a RAID stripe-tree backed
filesystem with pre-allocated extents will cause the RAID stripe-tree
lookup code to return ENODATA, as pre-allocated extents do not have any
on-disk bytes and thus no RAID stripe-tree entries.
But the current scrub read code marks these extents as errors, because
the lookup fails.
If btrfs_map_block() returns -ENODATA, it means that the call to
btrfs_get_raid_extent_offset() returned -ENODATA, because there is no
entry for the corresponding range in the RAID stripe-tree. But as this
range is in the extent tree it means we've hit a pre-allocated extent. In
this case, don't mark the sector in the stripe's error bitmaps as faulty
and carry on to the next.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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In case a lookup in the RAID stripe-tree fails, return ENODATA instead of
ENOENT to better distinguish stripe-tree lookups from other code paths
where we return ENOENT.
Suggested-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Currently we BUG_ON() in btrfs_finish_one_ordered() if we are finishing
an ordered extent that is flagged as NOCOW, but it's checksum list is
not empty.
This is clearly a logic error which we can recover from by aborting the
transaction.
For developer builds which enable CONFIG_BTRFS_ASSERT, also ASSERT()
that the list is empty.
Suggested-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Currently inside prepare_pages(), we handle the leading and tailing page
differently, and skip the middle pages (if any). This is to avoid
reading pages which are fully covered by the dirty range.
Refactor the code by moving all checks (alignment check, range check,
force read check) into prepare_uptodate_page().
So that prepare_pages() only needs to iterate all the pages
unconditionally.
And since we're here, also update prepare_uptodate_page() to use
folio API other than the old page API.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Inside btrfs_buffered_write(), we have a local variable @dirty_pages,
recording the number of pages we dirtied in the current iteration.
However we do not really need that variable, since it can be calculated
from @pos and @copied.
In fact there is already a problem inside the short copy path, where we
use @dirty_pages to calculate the range we need to release.
But that usage assumes sectorsize == PAGE_SIZE, which is no longer true.
Instead of keeping @dirty_pages and cause incorrect usage, just
calculate the number of dirtied pages inside btrfs_dirty_pages().
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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btrfs_try_tree_write_lock() has been unused since commit
50b21d7a066f ("btrfs: submit a writeback bio per extent_buffer").
Remove it as we don't need it anymore.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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btrfs_is_parity_mirror() has been unused since commit 4886ff7b50f6
("btrfs: introduce a new helper to submit write bio for repair").
Remove it as the code was refactored and we don't need the helper
anymore.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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btrfs_free_squota_rsv() was added in commit
e85a0adacf17 ("btrfs: ensure releasing squota reserve on head refs")
but has remained unused since then.
Remove it as we don't seem to need it and was probably a leftover.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Add first stash of very basic self tests for the RAID stripe-tree.
More test cases will follow exercising the tree.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Fix some confusing spelling errors that were currently identified,
the details are as follows:
block-group.c: 2800: uncompressible ==> incompressible
extent-tree.c: 3131: EXTEMT ==> EXTENT
extent_io.c: 3124: utlizing ==> utilizing
extent_map.c: 1323: ealier ==> earlier
extent_map.c: 1325: possiblity ==> possibility
fiemap.c: 189: emmitted ==> emitted
fiemap.c: 197: emmitted ==> emitted
fiemap.c: 203: emmitted ==> emitted
transaction.h: 36: trasaction ==> transaction
volumes.c: 5312: filesysmte ==> filesystem
zoned.c: 1977: trasnsaction ==> transaction
Signed-off-by: Shen Lichuan <shenlichuan@vivo.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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This macro is no longer used after the "btrfs: Cleaned up folio->page
conversion" series patch [1] was applied, so remove it.
[1]: https://patchwork.kernel.org/project/linux-btrfs/cover/20240828182908.3735344-1-lizetao1@huawei.com/
Reviewed-by: Neal Gompa <neal@gompa.dev>
Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The variable stop_loop was originally introduced in commit 625f1c8dc66d7
("Btrfs: improve the loop of scrub_stripe"). It was initialized to 0 in
commit 3b080b2564287 ("Btrfs: scrub raid56 stripes in the right way").
However, in a later commit 18d30ab961497 ("btrfs: scrub: use
scrub_simple_mirror() to handle RAID56 data stripe scrub"), the code
that modified stop_loop was removed, making the variable redundant.
Currently, stop_loop is only initialized with 0 and is never used or
modified within the scrub_stripe() function. As a result, this patch
removes the stop_loop variable to clean up the code and eliminate
unnecessary redundancy.
This change has no impact on functionality, as stop_loop was never
utilized in any meaningful way in the final version of the code.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Riyan Dhiman <riyandhiman14@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The qgroup record was allocated with kzalloc(), so it's pointless to set
its old_roots member to NULL. Remove the assignment.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Instead of dereferencing the delayed refs from the transaction multiple
times, store it early in the local variable and then always use the
variable.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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There's no need to hold the delayed refs spinlock when calling
btrfs_qgroup_trace_extent_nolock() from btrfs_qgroup_trace_extent(), since
it doesn't change anything in delayed refs and it only changes the xarray
used to track qgroup extent records, which is protected by the xarray's
lock.
Holding the lock is only adding unnecessary lock contention with other
tasks that actually need to take the lock to add/remove/change delayed
references. So remove the locking.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Instead of extracting fs_info from the transaction multiples times, store
it in a local variable and use it.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Now that we track qgroup extent records in a xarray we don't need to have
a "bytenr" field in struct btrfs_qgroup_extent_record, since we can get
it from the index of the record in the xarray.
So remove the field and grab the bytenr from either the index key or any
other place where it's available (delayed refs). This reduces the size of
struct btrfs_qgroup_extent_record from 40 bytes down to 32 bytes, meaning
that we now can store 128 instances of this structure instead of 102 per
4K page.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Remove the duplicated transaction joining, block reserve setting and raid
extent inserting in btrfs_finish_ordered_extent().
While at it, also abort the transaction in case inserting a RAID
stripe-tree entry fails.
Suggested-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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[PROBLEM]
Currently btrfs accepts any file path for its device, resulting some
weird situation:
# ./mount_by_fd /dev/test/scratch1 /mnt/btrfs/
The program has the following source code:
#include <fcntl.h>
#include <stdio.h>
#include <sys/mount.h>
int main(int argc, char *argv[]) {
int fd = open(argv[1], O_RDWR);
char path[256];
snprintf(path, sizeof(path), "/proc/self/fd/%d", fd);
return mount(path, argv[2], "btrfs", 0, NULL);
}
Then we can have the following weird device path:
BTRFS: device fsid 2378be81-fe12-46d2-a9e8-68cf08dd98d5 devid 1 transid 7 /proc/self/fd/3 (253:2) scanned by mount_by_fd (18440)
Normally it's not a big deal, and later udev can trigger a device path
rename. But if udev didn't trigger, the device path "/proc/self/fd/3"
will show up in mtab.
[CAUSE]
For filename "/proc/self/fd/3", it means the opened file descriptor 3.
In above case, it's exactly the device we want to open, aka points to
"/dev/test/scratch1" which is another symlink pointing to "/dev/dm-2".
Inside kernel we solve the mount source using LOOKUP_FOLLOW, which
follows the symbolic link and grab the proper block device.
But inside btrfs we also save the filename into btrfs_device::name, and
utilize that member to report our mount source, which leads to the above
situation.
[FIX]
Instead of unconditionally trust the path, check if the original file
(not following the symbolic link) is inside "/dev/", if not, then
manually lookup the path to its final destination, and use that as our
device path.
This allows us to still use symbolic links, like
"/dev/mapper/test-scratch" from LVM2, which is required for fstests runs
with LVM2 setup.
And for really weird names, like the above case, we solve it to
"/dev/dm-2" instead.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Link: https://bugzilla.suse.com/show_bug.cgi?id=1230641
Reported-by: Fabian Vogt <fvogt@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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[PROBLEM]
It is very common for udev to trigger device scan, and every time a
mounted btrfs device got re-scan from different soft links, we will get
some of unnecessary device path updates, this is especially common
for LVM based storage:
# lvs
scratch1 test -wi-ao---- 10.00g
scratch2 test -wi-a----- 10.00g
scratch3 test -wi-a----- 10.00g
scratch4 test -wi-a----- 10.00g
scratch5 test -wi-a----- 10.00g
test test -wi-a----- 10.00g
# mkfs.btrfs -f /dev/test/scratch1
# mount /dev/test/scratch1 /mnt/btrfs
# dmesg -c
[ 205.705234] BTRFS: device fsid 7be2602f-9e35-4ecf-a6ff-9e91d2c182c9 devid 1 transid 6 /dev/mapper/test-scratch1 (253:4) scanned by mount (1154)
[ 205.710864] BTRFS info (device dm-4): first mount of filesystem 7be2602f-9e35-4ecf-a6ff-9e91d2c182c9
[ 205.711923] BTRFS info (device dm-4): using crc32c (crc32c-intel) checksum algorithm
[ 205.713856] BTRFS info (device dm-4): using free-space-tree
[ 205.722324] BTRFS info (device dm-4): checking UUID tree
So far so good, but even if we just touched any soft link of
"dm-4", we will get quite some unnecessary device path updates.
# touch /dev/mapper/test-scratch1
# dmesg -c
[ 469.295796] BTRFS info: devid 1 device path /dev/mapper/test-scratch1 changed to /dev/dm-4 scanned by (udev-worker) (1221)
[ 469.300494] BTRFS info: devid 1 device path /dev/dm-4 changed to /dev/mapper/test-scratch1 scanned by (udev-worker) (1221)
Such device path rename is unnecessary and can lead to random path
change due to the udev race.
[CAUSE]
Inside device_list_add(), we are using a very primitive way checking if
the device has changed, strcmp().
Which can never handle links well, no matter if it's hard or soft links.
So every different link of the same device will be treated as a different
device, causing the unnecessary device path update.
[FIX]
Introduce a helper, is_same_device(), and use path_equal() to properly
detect the same block device.
So that the different soft links won't trigger the rename race.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Link: https://bugzilla.suse.com/show_bug.cgi?id=1230641
Reported-by: Fabian Vogt <fvogt@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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