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btrfs_update_block_group() accounts for the number of bytes allocated or
freed. Argument @alloc specifies whether the call is for alloc or free.
Convert the argument @alloc type from int to bool.
Reviewed-by: Su Yue <l@damenly.su>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Now that real_root is only used in ref-verify core gate it behind
CONFIG_BTRFS_FS_REF_VERIFY ifdef. This shrinks the size of pending
delayed refs by 8 bytes per ref, of which we can have many at any one
time depending on intensity of the workload. Also change the comment
about the member as it no longer deals with qgroups.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Instead of checking whether qgroup processing for a dealyed ref has to
happen in the core of delayed ref, simply pull the check at init time of
respective delayed ref structures. This eliminates the final use of
real_root in delayed-ref core paving the way to making this member
optional.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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In order to make 'real_root' used only in ref-verify it's required to
have the necessary context to perform the same checks that this member
is used for. So add 'mod_root' which will contain the root on behalf of
which a delayed ref was created and a 'skip_group' parameter which
will contain callsite-specific override of skip_qgroup.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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CHUNK_ROOT
The real_root field is going to be used only by ref-verify tool so limit
its use outside of it. Blocks belonging to the chunk root will always
have it as an owner so the check is equivalent.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Both data and metadata delayed ref structures have fields named
root/ref_root respectively. Those are somewhat cryptic and don't really
convey the real meaning. In fact those roots are really the original
owners of the respective block (i.e in case of a snapshot a data delayed
ref will contain the original root that owns the given block). Rename
those fields accordingly and adjust comments.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Error injection stressing uncovered a busy loop in our data reclaim
loop. There are two cases here, one where we loop creating block groups
until space_info->full is set, or in the main loop we will skip erroring
out any tickets if space_info->full == 0. Unfortunately if we aborted
the transaction then we will never allocate chunks or reclaim any space
and thus never get ->full, and you'll see stack traces like this:
watchdog: BUG: soft lockup - CPU#0 stuck for 26s! [kworker/u4:4:139]
CPU: 0 PID: 139 Comm: kworker/u4:4 Tainted: G W 5.13.0-rc1+ #328
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014
Workqueue: events_unbound btrfs_async_reclaim_data_space
RIP: 0010:btrfs_join_transaction+0x12/0x20
RSP: 0018:ffffb2b780b77de0 EFLAGS: 00000246
RAX: ffffb2b781863d58 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000801 RSI: ffff987952b57400 RDI: ffff987940aa3000
RBP: ffff987954d55000 R08: 0000000000000001 R09: ffff98795539e8f0
R10: 000000000000000f R11: 000000000000000f R12: ffffffffffffffff
R13: ffff987952b574c8 R14: ffff987952b57400 R15: 0000000000000008
FS: 0000000000000000(0000) GS:ffff9879bbc00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0703da4000 CR3: 0000000113398004 CR4: 0000000000370ef0
Call Trace:
flush_space+0x4a8/0x660
btrfs_async_reclaim_data_space+0x55/0x130
process_one_work+0x1e9/0x380
worker_thread+0x53/0x3e0
? process_one_work+0x380/0x380
kthread+0x118/0x140
? __kthread_bind_mask+0x60/0x60
ret_from_fork+0x1f/0x30
Fix this by checking to see if we have a btrfs fs error in either of the
reclaim loops, and if so fail the tickets and bail. In addition to
this, fix maybe_fail_all_tickets() to not try to grant tickets if we've
aborted, simply fail everything.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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We have a few flags that are inconsistently used to describe the fs in
different states of failure. As of 5963ffcaf383 ("btrfs: always abort
the transaction if we abort a trans handle") we will always set
BTRFS_FS_STATE_ERROR if we abort, so we don't have to check both ABORTED
and ERROR to see if things have gone wrong. Add a helper to check
BTRFS_FS_STATE_ERROR and then convert all checkers of FS_STATE_ERROR to
use the helper.
The TRANS_ABORTED bit check was added in af7227338135 ("Btrfs: clean up
resources during umount after trans is aborted") but is not actually
specific.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Currently we will abort the transaction if we get a random error (like
-EIO) while trying to remove the directory entries from the root log
during rename.
However since these are simply log tree related errors, we can mark the
trans as needing a full commit. Then if the error was truly
catastrophic we'll hit it during the normal commit and abort as
appropriate.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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During inspection of the return path for replay I noticed that we don't
actually abort the transaction if we get a failure during replay. This
isn't a problem necessarily, as we properly return the error and will
fail to mount. However we still leave this dangling transaction that
could conceivably be committed without thinking there was an error.
We were using btrfs_handle_fs_error() here, but that pre-dates the
transaction abort code. Simply replace the btrfs_handle_fs_error()
calls with transaction aborts, so we still know where exactly things
went wrong, and add a few in some other un-handled error cases.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Fix memdup.cocci warning:
fs/btrfs/zoned.c:1198:23-30: WARNING opportunity for kmemdup
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Kai Song <songkai01@inspur.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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For compressed write, we use a mechanism called async COW, which unlike
regular run_delalloc_cow() or cow_file_range() will also unlock the
first page.
This mechanism allows us to continue handling next ranges, without
waiting for the time consuming compression.
But this has a problem for subpage case, as we could have the following
delalloc range for a page:
0 32K 64K
| |///////| |///////|
\- A \- B
In the above case, if we pass both ranges to cow_file_range_async(),
both range A and range B will try to unlock the full page [0, 64K).
And which one finishes later than the other one will try to do other
page operations like end_page_writeback() on a unlocked page, triggering
VM layer BUG_ON().
To make subpage compression work at least partially, here we add another
restriction for it, only allow compression if the delalloc range is
fully page aligned.
By that, async extent is always ensured to unlock the first page
exclusively, just like it used to be for regular sectorsize.
In theory, we only need to make sure the delalloc range fully covers its
first page, but the tail page will be locked anyway, blocking later
writeback until the compression finishes.
Thus here we choose to make sure the range is fully page aligned before
doing the compression.
In the future, we could optimize the situation by properly increasing
subpage::writers number for the locked page, but that also means we need
to change how we run delalloc range of page.
(Instead of running each delalloc range we hit, we need to find and lock
all delalloc ranges covering the page, then run each of them).
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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[BUG]
With experimental subpage compression enabled, a simple fsstress can
lead to self deadlock on page 720896:
mkfs.btrfs -f -s 4k $dev > /dev/null
mount $dev -o compress $mnt
$fsstress -p 1 -n 100 -w -d $mnt -v -s 1625511156
[CAUSE]
If we have a file layout looks like below:
0 32K 64K 96K 128K
|//| |///////////////|
4K
Then we run delalloc range for the inode, it will:
- Call find_lock_delalloc_range() with @delalloc_start = 0
Then we got a delalloc range [0, 4K).
This range will be COWed.
- Call find_lock_delalloc_range() again with @delalloc_start = 4K
Since find_lock_delalloc_range() never cares whether the range
is still inside page range [0, 64K), it will return range [64K, 128K).
This range meets the condition for subpage compression, will go
through async COW path.
And async COW path will return @page_started.
But that @page_started is now for range [64K, 128K), not for range
[0, 64K).
- writepage_dellloc() returned 1 for page [0, 64K)
Thus page [0, 64K) will not be unlocked, nor its page dirty status
will be cleared.
Next time when we try to lock page [0, 64K) we will deadlock, as there
is no one to release page [0, 64K).
This problem will never happen for regular page size as one page only
contains one sector. After the first find_lock_delalloc_range() call,
the @delalloc_end will go beyond @page_end no matter if we found a
delalloc range or not
Thus this bug only happens for subpage, as now we need multiple runs to
exhaust the delalloc range of a page.
[FIX]
Fix the problem by ensuring the delalloc range we ran at least started
inside @locked_page.
So that we will never get incorrect @page_started.
And to prevent such problem from happening again:
- Make find_lock_delalloc_range() return false if the found range is
beyond @end value passed in.
Since @end will be utilized now, add an ASSERT() to ensure we pass
correct @end into find_lock_delalloc_range().
This also means, for selftests we needs to populate @end before calling
find_lock_delalloc_range().
- New ASSERT() in find_lock_delalloc_range()
Now we will make sure the @start/@end passed in at least covers part
of the page.
- New ASSERT() in run_delalloc_range()
To make sure the range at least starts inside @locked page.
- Use @delalloc_start as proper cursor, while @delalloc_end is always
reset to @page_end.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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There are several call sites of extent_clear_unlock_delalloc() which get
@locked_page = NULL.
So that extent_clear_unlock_delalloc() will try to call
process_one_page() to unlock every page even the first page is not
locked by btrfs_page_start_writer_lock().
This will trigger an ASSERT() in btrfs_subpage_end_and_test_writer() as
previously we require every page passed to
btrfs_subpage_end_and_test_writer() to be locked by
btrfs_page_start_writer_lock().
But compression path doesn't go that way.
Thankfully it's not hard to distinguish page locked by lock_page() and
btrfs_page_start_writer_lock().
So do the check in btrfs_subpage_end_and_test_writer() so now it can
handle both cases well.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Pages passed to __extent_writepage() are always locked, but they may be
locked by different functions.
There are two types of locked page for __extent_writepage():
- Page locked by plain lock_page()
It should not have any subpage::writers count.
Can be unlocked by unlock_page().
This is the most common locked page for __extent_writepage() called
inside extent_write_cache_pages() or extent_write_full_page().
Rarer cases include the @locked_page from extent_write_locked_range().
- Page locked by lock_delalloc_pages()
There is only one caller, all pages except @locked_page for
extent_write_locked_range().
In this case, we have to call subpage helper to handle the case.
So here we introduce a helper, btrfs_page_unlock_writer(), to allow
__extent_writepage() to unlock different locked pages.
And since for all other callers of __extent_writepage() their pages are
ensured to be locked by lock_page(), also add an extra check for
epd::extent_locked to unlock such pages directly.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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There are several problems in lzo_compress_pages() preventing it from
being subpage compatible:
- No page offset is calculated when reading from inode pages
For subpage case, we could have @start which is not aligned to
PAGE_SIZE.
Thus the destination where we read data from must take offset in page
into consideration.
- The padding for segment header is bound to PAGE_SIZE
This means, for subpage case we can skip several corners where on x86
machines we need to add padding zeros.
The rework will:
- Update the comment to replace "page" with "sector"
- Introduce a new helper, copy_compressed_data_to_page(), to do the copy
So that we don't need to bother page switching for both input and
output.
Now in lzo_compress_pages() we only care about page switching for
input, while in copy_compressed_data_to_page() we only care about the
page switching for output.
- Only one main cursor
For lzo_compress_pages() we use @cur_in as main cursor.
It will be the file offset we are currently at.
All other helper variables will be only declared inside the loop.
For copy_compressed_data_to_page() it's similar, we will have
@cur_out at the main cursor, which records how many bytes are in the
output.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Introduce a new helper, submit_uncompressed_range(), for async cow cases
where we fallback to COW.
There are some new updates introduced to the helper:
- Proper locked_page detection
It's possible that the async_extent range doesn't cover the locked
page. In that case we shouldn't unlock the locked page.
In the new helper, we will ensure that we only unlock the locked page
when:
* The locked page covers part of the async_extent range
* The locked page is not unlocked by cow_file_range() nor
extent_write_locked_range()
This also means extra comments are added focusing on the page locking.
- Add extra comment on some rare parameter used.
We use @unlock_page = 0 for cow_file_range(), where only two call
sites doing the same thing, including the new helper.
It's definitely worth some comments.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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There are two sites are not subpage compatible yet for
extent_write_locked_range():
- How @nr_pages are calculated
For subpage we can have the following range with 64K page size:
0 32K 64K 96K 128K
| |////|/////| |
In that case, although 96K - 32K == 64K, thus it looks like one page
is enough, but the range spans two pages, not one.
Fix it by doing proper round_up() and round_down() to calculate
@nr_pages.
Also add some extra ASSERT()s to ensure the range passed in is already
aligned.
- How the page end is calculated
Currently we just use cur + PAGE_SIZE - 1 to calculate the page end.
Which can't handle the above range layout, and will trigger ASSERT()
in btrfs_writepage_endio_finish_ordered(), as the range is no longer
covered by the page range.
Fix it by taking page end into consideration.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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In end_compressed_writeback() we just clear the full page writeback.
For subpage case, if there are two delalloc ranges in the same page, the
2nd range will trigger a BUG_ON() as the page writeback is already
cleared by previous range.
Fix it by using btrfs_page_clamp_clear_writeback() helper.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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There is a WARN_ON() checking if @start is aligned to PAGE_SIZE, not
sectorsize, which will cause false alert for subpage. Fix it to check
against sectorsize.
Furthermore:
- Use ASSERT() to do the check
So that in the future we may skip the check for production build
- Also check alignment for @len
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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In function compress_file_range(), when the compression is finished, the
function just rounds up @total_in to PAGE_SIZE. This is fine for
regular sectorsize == PAGE_SIZE case, but not for subpage.
Just change the ALIGN(, PAGE_SIZE) to round_up(, sectorsize) so that
both regular sectorsize and subpage sectorsize will be happy.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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There are several cleanups for extent_write_locked_range(), most of them
are pure cleanups, but with some preparation for future subpage support.
- Add a proper comment for which call sites are suitable
Unlike regular synchronized extent write back, if async COW or zoned
COW happens, we have all pages in the range still locked.
Thus for those (only) two call sites, we need this function to submit
page content into bios and submit them.
- Remove @mode parameter
All the existing two call sites pass WB_SYNC_ALL. No need for @mode
parameter.
- Better error handling
Currently if we hit an error during the page iteration loop, we
overwrite @ret, causing only the last error can be recorded.
Here we add @found_error and @first_error variable to record if we hit
any error, and the first error we hit.
So the first error won't get lost.
- Don't reuse @start as the cursor
We reuse the parameter @start as the cursor to iterate the range, not
a big problem, but since we're here, introduce a proper @cur as the
cursor.
- Remove impossible branch
Since all pages are still locked after the ordered extent is inserted,
there is no way that pages can get its dirty bit cleared.
Remove the branch where page is not dirty and replace it with an
ASSERT().
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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We have a big chunk of code inside a while() loop, with tons of strange
jumps for error handling. It's definitely not to the code standard of
today. Move the code into a new function, submit_one_async_extent().
Since we're here, also do the following changes:
- Comment style change
To follow the current scheme
- Don't fallback to non-compressed write then hitting ENOSPC
If we hit ENOSPC for compressed write, how could we reserve more space
for non-compressed write?
Thus we go error path directly.
This removes the retry: label.
- Add more comment for super long parameter list
Explain which parameter is for, so we don't need to check the
prototype.
- Move the error handling to submit_one_async_extent()
Thus no strange code like:
out_free:
...
goto again;
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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As the last caller in compression.c has been removed, we don't need that
function anymore.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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btrfs_submit_compressed_write
Currently btrfs_submit_compressed_write() will check
btrfs_bio_fits_in_stripe() each time a new page is going to be added.
Even if compressed extent is small, we don't really need to do that for
every page.
Align the behavior to extent_io.c, by determining the stripe boundary
when allocating a bio.
Unlike extent_io.c, in compressed.c we don't need to bother things like
different bio flags, thus no need to re-use bio_ctrl.
Here we just manually introduce new local variable, next_stripe_start,
and use that value returned from alloc_compressed_bio() to calculate
the stripe boundary.
Then each time we add some page range into the bio, we check if we
reached the boundary. And if reached, submit it.
Also, since we have @cur_disk_bytenr to determine whether we're the last
bio, we don't need a explicit last_bio: tag for error handling any more.
And since we use @cur_disk_bytenr to wait, there is no need for
pending_bios, also remove it to save some memory of compressed_bio.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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btrfs_submit_compressed_read
Currently btrfs_submit_compressed_read() will check
btrfs_bio_fits_in_stripe() each time a new page is going to be added.
Even if compressed extent is small, we don't really need to do that for
every page.
This patch will align the behavior to extent_io.c, by determining the
stripe boundary when allocating a bio.
Unlike extent_io.c, in compressed.c we don't need to bother things like
different bio flags, thus no need to re-use bio_ctrl.
Here we just manually introduce new local variable, next_stripe_start,
and teach alloc_compressed_bio() to calculate the stripe boundary.
Then each time we add some page range into the bio, we check if we
reached the boundary. And if reached, submit it.
Also, since we have @cur_disk_byte to determine whether we're the last
bio, we don't need a explicit last_bio: tag for error handling any more.
And we can use @cur_disk_byte to track which range has been added to
bio, we can also use @cur_disk_byte to calculate the wait condition, no
need for @pending_bios.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Just aggregate the bio allocation code into one helper, so that we can
replace 4 call sites.
There is one special note for zoned write.
Currently btrfs_submit_compressed_write() will only allocate the first
bio using ZONE_APPEND. If we have to submit current bio due to stripe
boundary, the new bio allocated will not use ZONE_APPEND.
In theory this should be a bug, but considering zoned mode currently
only support SINGLE profile, which doesn't have any stripe boundary
limit, it should never be a problem and we have assertions in place.
This function will provide a good entrance for any work which needs to
be done at bio allocation time. Like determining the stripe boundary.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The new helper, submit_compressed_bio(), will aggregate the following
work:
- Increase compressed_bio::pending_bios
- Remap the endio function
- Map and submit the bio
This slightly reorders calls to btrfs_csum_one_bio or
btrfs_lookup_bio_sums but but none of them does anything regarding IO
submission so this is effectively no change. We mainly care about order
of
- atomic_inc
- btrfs_bio_wq_end_io
- btrfs_map_bio
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Just like btrfs_submit_compressed_read(), there are quite some BUG_ON()s
inside btrfs_submit_compressed_write() for the bio submission path.
Fix them using the same method:
- For last bio, just endio the bio
As in that case, one of the endio function of all these submitted bio
will be able to free the compressed_bio
- For half-submitted bio, wait and finish the compressed_bio manually
In this case, as long as all other bio finish, we're the only one
referring the compressed bio, and can manually finish it.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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There are quite some BUG_ON()s inside btrfs_submit_compressed_read(),
namely all errors inside the for() loop relies on BUG_ON() to handle
-ENOMEM.
Handle these errors properly by:
- Wait for submitted bios to finish first
Using wake_var_event() APIs to wait without introducing extra memory
overhead inside compressed_bio.
This allows us to wait for any submitted bio to finish, while still
keeps the compressed_bio from being freed.
- Introduce finish_compressed_bio_read() to finish the compressed_bio
- Properly end the bio and finish compressed_bio when error happens
Now in btrfs_submit_compressed_read() even when the bio submission
failed, we can properly handle the error without triggering BUG_ON().
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Although in btrfs we have very limited usage of PageChecked flag, it's
still some page flag not yet subpage compatible.
Fix it by introducing btrfs_subpage::checked_offset to do the convert.
For most call sites, especially for free-space cache, COW fixup and
btrfs_invalidatepage(), they all work in full page mode anyway.
For other call sites, they work as subpage compatible mode.
Some call sites need extra modification:
- btrfs_drop_pages()
Needs extra parameter to get the real range we need to clear checked
flag.
Also since btrfs_drop_pages() will accept pages beyond the dirtied
range, update btrfs_subpage_clamp_range() to handle such case
by setting @len to 0 if the page is beyond target range.
- btrfs_invalidatepage()
We need to call subpage helper before calling __btrfs_releasepage(),
or it will trigger ASSERT() as page->private will be cleared.
- btrfs_verify_data_csum()
In theory we don't need the io_bio->csum check anymore, but it's
won't hurt. Just change the comment.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
For btrfs_submit_compressed_read() and btrfs_submit_compressed_write(),
we have a pretty weird dance around compressed_bio::pending_bios:
btrfs_submit_compressed_read/write()
{
cb = kmalloc()
refcount_set(&cb->pending_bios, 0);
bio = btrfs_alloc_bio();
/* NOTE here, we haven't yet submitted any bio */
refcount_set(&cb->pending_bios, 1);
for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) {
if (submit) {
/* Here we submit bio, but we always have one
* extra pending_bios */
refcount_inc(&cb->pending_bios);
ret = btrfs_map_bio();
}
}
/* Submit the last bio */
ret = btrfs_map_bio();
}
There are two reasons why we do this:
- compressed_bio::pending_bios is a refcount
Thus if it's reduced to 0, it can not be increased again.
- To ensure the compressed_bio is not freed by some submitted bios
If the submitted bio is finished before the next bio submitted,
we can free the compressed_bio completely.
But the above code is sometimes confusing, and we can do it better by
introducing a new member, compressed_bio::pending_sectors.
Now we use compressed_bio::pending_sectors to indicate whether we have
any pending sectors under IO or not yet submitted.
If pending_sectors == 0, we're definitely the last bio of compressed_bio,
and is OK to release the compressed bio.
Now the workflow looks like this:
btrfs_submit_compressed_read/write()
{
cb = kmalloc()
atomic_set(&cb->pending_bios, 0);
refcount_set(&cb->pending_sectors,
compressed_len >> sectorsize_bits);
bio = btrfs_alloc_bio();
for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) {
if (submit) {
refcount_inc(&cb->pending_bios);
ret = btrfs_map_bio();
}
}
/* Submit the last bio */
refcount_inc(&cb->pending_bios);
ret = btrfs_map_bio();
}
For now we still need pending_bios for later error handling, but will
remove pending_bios eventually after properly handling the errors.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
[BUG]
If we remove the subpage limitation in add_ra_bio_pages(), then read a
compressed extent which has part of its range in next page, like the
following inode layout:
0 32K 64K 96K 128K
|<--------------|-------------->|
Btrfs will trigger ASSERT() in endio function:
assertion failed: atomic_read(&subpage->readers) >= nbits
------------[ cut here ]------------
kernel BUG at fs/btrfs/ctree.h:3431!
Internal error: Oops - BUG: 0 [#1] SMP
Workqueue: btrfs-endio btrfs_work_helper [btrfs]
Call trace:
assertfail.constprop.0+0x28/0x2c [btrfs]
btrfs_subpage_end_reader+0x148/0x14c [btrfs]
end_page_read+0x8c/0x100 [btrfs]
end_bio_extent_readpage+0x320/0x6b0 [btrfs]
bio_endio+0x15c/0x1dc
end_workqueue_fn+0x44/0x64 [btrfs]
btrfs_work_helper+0x74/0x250 [btrfs]
process_one_work+0x1d4/0x47c
worker_thread+0x180/0x400
kthread+0x11c/0x120
ret_from_fork+0x10/0x30
---[ end trace c8b7b552d3bb408c ]---
[CAUSE]
When we read the page range [0, 64K), we find it's a compressed extent,
and we will try to add extra pages in add_ra_bio_pages() to avoid
reading the same compressed extent.
But when we add such page into the read bio, it doesn't follow the
behavior of btrfs_do_readpage() to properly set subpage::readers.
This means, for page [64K, 128K), its subpage::readers is still 0.
And when endio is executed on both pages, since page [64K, 128K) has 0
subpage::readers, it triggers above ASSERT()
[FIX]
Function add_ra_bio_pages() is far from subpage compatible, it always
assume PAGE_SIZE == sectorsize, thus when it skip to next range it
always just skip PAGE_SIZE.
Make it subpage compatible by:
- Skip to next page properly when needed
If we find there is already a page cache, we need to skip to next page.
For that case, we shouldn't just skip PAGE_SIZE bytes, but use
@pg_index to calculate the next bytenr and continue.
- Only add the page range covered by current extent map
We need to calculate which range is covered by current extent map and
only add that part into the read bio.
- Update subpage::readers before submitting the bio
- Use proper cursor other than confusing @last_offset
- Calculate the missed threshold based on sector size
It's no longer using missed pages, as for 64K page size, we have at
most 3 pages to skip. (If aligned only 2 pages)
- Add ASSERT() to make sure our bytenr is always aligned
- Add comment for the function
Add a special note for subpage case, as the function won't really
work well for subpage cases.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Since async_extent holds the compressed page, it would trigger the new
ASSERT() in btrfs_mark_ordered_io_finished() which checks that the range
is inside the page.
Now btrfs_writepage_endio_finish_ordered() can accept @page == NULL,
just pass NULL to btrfs_writepage_endio_finish_ordered().
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
For structure async_chunk, we use a very strange member layout to grab
structure async_cow who owns this async_chunk.
At initialization, it goes like this:
async_chunk[i].pending = &ctx->num_chunks;
Then at async_cow_free() we do a super weird freeing:
/*
* Since the pointer to 'pending' is at the beginning of the array of
* async_chunk's, freeing it ensures the whole array has been freed.
*/
if (atomic_dec_and_test(async_chunk->pending))
kvfree(async_chunk->pending);
This is absolutely an abuse of kvfree().
Replace async_chunk::pending with async_chunk::async_cow, so that we can
grab the async_cow structure directly, without this strange dancing.
And with this change, there is no requirement for any specific member
location.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
In function __extent_writepage() we always pass page start to
@delalloc_start for writepage_delalloc().
Thus we don't really need @delalloc_start parameter as we can extract it
from @page.
Remove @delalloc_start parameter and make __extent_writepage() to
declare @page_start and @page_end as const.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Variable @nr_pages only gets increased but never used. Remove it.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
When logging a directory and inserting a batch of directory items, we are
copying the data of each item from a leaf in the fs/subvolume tree to a
leaf in a log tree, separately. This is not really needed, since we are
copying from a contiguous memory area into another one, so we can use a
single copy operation to copy all items at once.
This patch is part of a small patchset that is comprised of the following
patches:
btrfs: loop only once over data sizes array when inserting an item batch
btrfs: unexport setup_items_for_insert()
btrfs: use single bulk copy operations when logging directories
This is patch 3/3.
The following test was used to compare performance of a branch without the
patchset versus one branch that has the whole patchset applied:
$ cat dir-fsync-test.sh
#!/bin/bash
DEV=/dev/nvme0n1
MNT=/mnt/nvme0n1
NUM_NEW_FILES=1000000
NUM_FILE_DELETES=1000
LEAF_SIZE=16K
mkfs.btrfs -f -n $LEAF_SIZE $DEV
mount -o ssd $DEV $MNT
mkdir $MNT/testdir
for ((i = 1; i <= $NUM_NEW_FILES; i++)); do
echo -n > $MNT/testdir/file_$i
done
# Fsync the directory, this will log the new dir items and the inodes
# they point to, because these are new inodes.
start=$(date +%s%N)
xfs_io -c "fsync" $MNT/testdir
end=$(date +%s%N)
dur=$(( (end - start) / 1000000 ))
echo "dir fsync took $dur ms after adding $NUM_NEW_FILES files"
# sync to force transaction commit and wipeout the log.
sync
del_inc=$(( $NUM_NEW_FILES / $NUM_FILE_DELETES ))
for ((i = 1; i <= $NUM_NEW_FILES; i += $del_inc)); do
rm -f $MNT/testdir/file_$i
done
# Fsync the directory, this will only log dir items, there are no
# dentries pointing to new inodes.
start=$(date +%s%N)
xfs_io -c "fsync" $MNT/testdir
end=$(date +%s%N)
dur=$(( (end - start) / 1000000 ))
echo "dir fsync took $dur ms after deleting $NUM_FILE_DELETES files"
umount $MNT
The tests were run on a non-debug kernel (Debian's default kernel config)
and were the following:
*** with a leaf size of 16K, before patchset ***
dir fsync took 8482 ms after adding 1000000 files
dir fsync took 166 ms after deleting 1000 files
*** with a leaf size of 16K, after patchset ***
dir fsync took 8196 ms after adding 1000000 files (-3.4%)
dir fsync took 143 ms after deleting 1000 files (-14.9%)
*** with a leaf size of 64K, before patchset ***
dir fsync took 12851 ms after adding 1000000 files
dir fsync took 466 ms after deleting 1000 files
*** with a leaf size of 64K, after patchset ***
dir fsync took 12287 ms after adding 1000000 files (-4.5%)
dir fsync took 414 ms after deleting 1000 files (-11.8%)
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Since setup_items_for_insert() is not used anymore outside of ctree.c,
make it static and remove its prototype from ctree.h. This also requires
to move the definition of setup_item_for_insert() from ctree.h to ctree.c
and move down btrfs_duplicate_item() so that it's defined after
setup_items_for_insert().
Further, since setup_item_for_insert() is used outside ctree.c, rename it
to btrfs_setup_item_for_insert().
This patch is part of a small patchset that is comprised of the following
patches:
btrfs: loop only once over data sizes array when inserting an item batch
btrfs: unexport setup_items_for_insert()
btrfs: use single bulk copy operations when logging directories
This is patch 2/3 and performance results, and the specific tests, are
included in the changelog of patch 3/3.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
When inserting a batch of items into a btree, we end up looping over the
data sizes array 3 times:
1) Once in the caller of btrfs_insert_empty_items(), when it populates the
array with the data sizes for each item;
2) Once at btrfs_insert_empty_items() to sum the elements of the data
sizes array and compute the total data size;
3) And then once again at setup_items_for_insert(), where we do exactly
the same as what we do at btrfs_insert_empty_items(), to compute the
total data size.
That is not bad for small arrays, but when the arrays have hundreds of
elements, the time spent on looping is not negligible. For example when
doing batch inserts of delayed items for dir index items or when logging
a directory, it's common to have 200 to 260 dir index items in a single
batch when using a leaf size of 16K and using file names between 8 and 12
characters. For a 64K leaf size, multiply that by 4. Taking into account
that during directory logging or when flushing delayed dir index items we
can have many of those large batches, the time spent on the looping adds
up quickly.
It's also more important to avoid it at setup_items_for_insert(), since
we are holding a write lock on a leaf and, in some cases, on upper nodes
of the btree, which causes us to block other tasks that want to access
the leaf and nodes for longer than necessary.
So change the code so that setup_items_for_insert() and
btrfs_insert_empty_items() no longer compute the total data size, and
instead rely on the caller to supply it. This makes us loop over the
array only once, where we can both populate the data size array and
compute the total data size, taking advantage of spatial and temporal
locality. To make this more manageable, use a structure to contain
all the relevant details for a batch of items (keys array, data sizes
array, total data size, number of items), and use it as an argument
for btrfs_insert_empty_items() and setup_items_for_insert().
This patch is part of a small patchset that is comprised of the following
patches:
btrfs: loop only once over data sizes array when inserting an item batch
btrfs: unexport setup_items_for_insert()
btrfs: use single bulk copy operations when logging directories
This is patch 1/3 and performance results, and the specific tests, are
included in the changelog of patch 3/3.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
We can grab fs_info reliably from btrfs_raid_bio::bioc, as the bioc is
always passed into alloc_rbio(), and only get released when the raid bio
is released.
Remove btrfs_raid_bio::fs_info member, and cleanup all the @fs_info
parameters for alloc_rbio() callers.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Currently btrfs_io_context::fs_info is only initialized in
btrfs_map_bio, but there are call sites like btrfs_map_sblock() which
calls __btrfs_map_block() directly, leaving bioc::fs_info uninitialized
(NULL).
Currently this is fine, but later cleanup will rely on bioc::fs_info to
grab fs_info, and this can be a hidden problem for such usage.
This patch will remove such hidden uninitialized member by always
assigning bioc::fs_info at alloc_btrfs_io_context().
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
We currently use lockdep_assert_held() at btrfs_assert_tree_locked(), and
that checks that we hold a lock either in read mode or write mode.
However in all contexts we use btrfs_assert_tree_locked(), we actually
want to check if we are holding a write lock on the extent buffer's rw
semaphore - it would be a bug if in any of those contexts we were holding
a read lock instead.
So change btrfs_assert_tree_locked() to use lockdep_assert_held_write()
instead and, to make it more explicit, rename btrfs_assert_tree_locked()
to btrfs_assert_tree_write_locked(), so that it's clear we want to check
we are holding a write lock.
For now there are no contexts where we want to assert that we must have
a read lock, but in case that is needed in the future, we can add a new
helper function that just calls out lockdep_assert_held_read().
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
We got the following lockdep splat while running fstests (specifically
btrfs/003 and btrfs/020 in a row) with the new rc. This was uncovered
by 87579e9b7d8d ("loop: use worker per cgroup instead of kworker") which
converted loop to using workqueues, which comes with lockdep
annotations that don't exist with kworkers. The lockdep splat is as
follows:
WARNING: possible circular locking dependency detected
5.14.0-rc2-custom+ #34 Not tainted
------------------------------------------------------
losetup/156417 is trying to acquire lock:
ffff9c7645b02d38 ((wq_completion)loop0){+.+.}-{0:0}, at: flush_workqueue+0x84/0x600
but task is already holding lock:
ffff9c7647395468 (&lo->lo_mutex){+.+.}-{3:3}, at: __loop_clr_fd+0x41/0x650 [loop]
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #5 (&lo->lo_mutex){+.+.}-{3:3}:
__mutex_lock+0xba/0x7c0
lo_open+0x28/0x60 [loop]
blkdev_get_whole+0x28/0xf0
blkdev_get_by_dev.part.0+0x168/0x3c0
blkdev_open+0xd2/0xe0
do_dentry_open+0x163/0x3a0
path_openat+0x74d/0xa40
do_filp_open+0x9c/0x140
do_sys_openat2+0xb1/0x170
__x64_sys_openat+0x54/0x90
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae
-> #4 (&disk->open_mutex){+.+.}-{3:3}:
__mutex_lock+0xba/0x7c0
blkdev_get_by_dev.part.0+0xd1/0x3c0
blkdev_get_by_path+0xc0/0xd0
btrfs_scan_one_device+0x52/0x1f0 [btrfs]
btrfs_control_ioctl+0xac/0x170 [btrfs]
__x64_sys_ioctl+0x83/0xb0
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae
-> #3 (uuid_mutex){+.+.}-{3:3}:
__mutex_lock+0xba/0x7c0
btrfs_rm_device+0x48/0x6a0 [btrfs]
btrfs_ioctl+0x2d1c/0x3110 [btrfs]
__x64_sys_ioctl+0x83/0xb0
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae
-> #2 (sb_writers#11){.+.+}-{0:0}:
lo_write_bvec+0x112/0x290 [loop]
loop_process_work+0x25f/0xcb0 [loop]
process_one_work+0x28f/0x5d0
worker_thread+0x55/0x3c0
kthread+0x140/0x170
ret_from_fork+0x22/0x30
-> #1 ((work_completion)(&lo->rootcg_work)){+.+.}-{0:0}:
process_one_work+0x266/0x5d0
worker_thread+0x55/0x3c0
kthread+0x140/0x170
ret_from_fork+0x22/0x30
-> #0 ((wq_completion)loop0){+.+.}-{0:0}:
__lock_acquire+0x1130/0x1dc0
lock_acquire+0xf5/0x320
flush_workqueue+0xae/0x600
drain_workqueue+0xa0/0x110
destroy_workqueue+0x36/0x250
__loop_clr_fd+0x9a/0x650 [loop]
lo_ioctl+0x29d/0x780 [loop]
block_ioctl+0x3f/0x50
__x64_sys_ioctl+0x83/0xb0
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae
other info that might help us debug this:
Chain exists of:
(wq_completion)loop0 --> &disk->open_mutex --> &lo->lo_mutex
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&lo->lo_mutex);
lock(&disk->open_mutex);
lock(&lo->lo_mutex);
lock((wq_completion)loop0);
*** DEADLOCK ***
1 lock held by losetup/156417:
#0: ffff9c7647395468 (&lo->lo_mutex){+.+.}-{3:3}, at: __loop_clr_fd+0x41/0x650 [loop]
stack backtrace:
CPU: 8 PID: 156417 Comm: losetup Not tainted 5.14.0-rc2-custom+ #34
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
Call Trace:
dump_stack_lvl+0x57/0x72
check_noncircular+0x10a/0x120
__lock_acquire+0x1130/0x1dc0
lock_acquire+0xf5/0x320
? flush_workqueue+0x84/0x600
flush_workqueue+0xae/0x600
? flush_workqueue+0x84/0x600
drain_workqueue+0xa0/0x110
destroy_workqueue+0x36/0x250
__loop_clr_fd+0x9a/0x650 [loop]
lo_ioctl+0x29d/0x780 [loop]
? __lock_acquire+0x3a0/0x1dc0
? update_dl_rq_load_avg+0x152/0x360
? lock_is_held_type+0xa5/0x120
? find_held_lock.constprop.0+0x2b/0x80
block_ioctl+0x3f/0x50
__x64_sys_ioctl+0x83/0xb0
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f645884de6b
Usually the uuid_mutex exists to protect the fs_devices that map
together all of the devices that match a specific uuid. In rm_device
we're messing with the uuid of a device, so it makes sense to protect
that here.
However in doing that it pulls in a whole host of lockdep dependencies,
as we call mnt_may_write() on the sb before we grab the uuid_mutex, thus
we end up with the dependency chain under the uuid_mutex being added
under the normal sb write dependency chain, which causes problems with
loop devices.
We don't need the uuid mutex here however. If we call
btrfs_scan_one_device() before we scratch the super block we will find
the fs_devices and not find the device itself and return EBUSY because
the fs_devices is open. If we call it after the scratch happens it will
not appear to be a valid btrfs file system.
We do not need to worry about other fs_devices modifying operations here
because we're protected by the exclusive operations locking.
So drop the uuid_mutex here in order to fix the lockdep splat.
A more detailed explanation from the discussion:
We are worried about rm and scan racing with each other, before this
change we'll zero the device out under the UUID mutex so when scan does
run it'll make sure that it can go through the whole device scan thing
without rm messing with us.
We aren't worried if the scratch happens first, because the result is we
don't think this is a btrfs device and we bail out.
The only case we are concerned with is we scratch _after_ scan is able
to read the superblock and gets a seemingly valid super block, so lets
consider this case.
Scan will call device_list_add() with the device we're removing. We'll
call find_fsid_with_metadata_uuid() and get our fs_devices for this
UUID. At this point we lock the fs_devices->device_list_mutex. This is
what protects us in this case, but we have two cases here.
1. We aren't to the device removal part of the RM. We found our device,
and device name matches our path, we go down and we set total_devices
to our super number of devices, which doesn't affect anything because
we haven't done the remove yet.
2. We are past the device removal part, which is protected by the
device_list_mutex. Scan doesn't find the device, it goes down and
does the
if (fs_devices->opened)
return -EBUSY;
check and we bail out.
Nothing about this situation is ideal, but the lockdep splat is real,
and the fix is safe, tho admittedly a bit scary looking.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ copy more from the discussion ]
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Previously we had "struct btrfs_bio", which records IO context for
mirrored IO and RAID56, and "strcut btrfs_io_bio", which records extra
btrfs specific info for logical bytenr bio.
With "btrfs_bio" renamed to "btrfs_io_context", we are safe to rename
"btrfs_io_bio" to "btrfs_bio" which is a more suitable name now.
The struct btrfs_bio changes meaning by this commit. There was a
suggested name like btrfs_logical_bio but it's a bit long and we'd
prefer to use a shorter name.
This could be a concern for backports to older kernels where the
different meaning could possibly cause confusion or bugs. Comparing the
new and old structures, there's no overlap among the struct members so a
build would break in case of incorrect backport.
We haven't had many backports to bio code anyway so this is more of a
theoretical cause of bugs and a matter of precaution but we'll need to
keep the semantic change in mind.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
The helper btrfs_bio_alloc() is almost the same as btrfs_io_bio_alloc(),
except it's allocating using BIO_MAX_VECS as @nr_iovecs, and initializes
bio->bi_iter.bi_sector.
However the naming itself is not using "btrfs_io_bio" to indicate its
parameter is "strcut btrfs_io_bio" and can be easily confused with
"struct btrfs_bio".
Considering assigned bio->bi_iter.bi_sector is such a simple work and
there are already tons of call sites doing that manually, there is no
need to do that in a helper.
Remove btrfs_bio_alloc() helper, and enhance btrfs_io_bio_alloc()
function to provide a fail-safe value for its @nr_iovecs.
And then replace all btrfs_bio_alloc() callers with
btrfs_io_bio_alloc().
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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The structure btrfs_bio is used by two different sites:
- bio->bi_private for mirror based profiles
For those profiles (SINGLE/DUP/RAID1*/RAID10), this structures records
how many mirrors are still pending, and save the original endio
function of the bio.
- RAID56 code
In that case, RAID56 only utilize the stripes info, and no long uses
that to trace the pending mirrors.
So btrfs_bio is not always bind to a bio, and contains more info for IO
context, thus renaming it will make the naming less confusing.
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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After the first time we log a directory in the current transaction, for
each directory item in a changed leaf of the subvolume tree, we have to
check if we previously logged the item, in order to overwrite it in case
its data changed or skip it in case its data hasn't changed.
Checking if we have logged each item before not only wastes times, but it
also adds lock contention on the log tree. So in order to minimize the
number of times we do such checks, keep track of the offset of the last
key we logged for a directory and, on the next time we log the directory,
skip the checks for any new keys that have an offset greater than the
offset we have previously saved. This is specially effective for index
keys, because the offset for these keys comes from a monotonically
increasing counter.
This patch is part of a patchset comprised of the following 5 patches:
btrfs: remove root argument from btrfs_log_inode() and its callees
btrfs: remove redundant log root assignment from log_dir_items()
btrfs: factor out the copying loop of dir items from log_dir_items()
btrfs: insert items in batches when logging a directory when possible
btrfs: keep track of the last logged keys when logging a directory
This is patch 5/5.
The following test was used on a non-debug kernel to measure the impact
it has on a directory fsync:
$ cat test-dir-fsync.sh
#!/bin/bash
DEV=/dev/nvme0n1
MNT=/mnt/nvme0n1
NUM_NEW_FILES=100000
NUM_FILE_DELETES=1000
mkfs.btrfs -f $DEV
mount -o ssd $DEV $MNT
mkdir $MNT/testdir
for ((i = 1; i <= $NUM_NEW_FILES; i++)); do
echo -n > $MNT/testdir/file_$i
done
# fsync the directory, this will log the new dir items and the inodes
# they point to, because these are new inodes.
start=$(date +%s%N)
xfs_io -c "fsync" $MNT/testdir
end=$(date +%s%N)
dur=$(( (end - start) / 1000000 ))
echo "dir fsync took $dur ms after adding $NUM_NEW_FILES files"
# sync to force transaction commit and wipeout the log.
sync
del_inc=$(( $NUM_NEW_FILES / $NUM_FILE_DELETES ))
for ((i = 1; i <= $NUM_NEW_FILES; i += $del_inc)); do
rm -f $MNT/testdir/file_$i
done
# fsync the directory, this will only log dir items, there are no
# dentries pointing to new inodes.
start=$(date +%s%N)
xfs_io -c "fsync" $MNT/testdir
end=$(date +%s%N)
dur=$(( (end - start) / 1000000 ))
echo "dir fsync took $dur ms after deleting $NUM_FILE_DELETES files"
umount $MNT
Test results with NUM_NEW_FILES set to 100 000 and 1 000 000:
**** before patchset, 100 000 files, 1000 deletes ****
dir fsync took 848 ms after adding 100000 files
dir fsync took 175 ms after deleting 1000 files
**** after patchset, 100 000 files, 1000 deletes ****
dir fsync took 758 ms after adding 100000 files (-11.2%)
dir fsync took 63 ms after deleting 1000 files (-94.1%)
**** before patchset, 1 000 000 files, 1000 deletes ****
dir fsync took 9945 ms after adding 1000000 files
dir fsync took 473 ms after deleting 1000 files
**** after patchset, 1 000 000 files, 1000 deletes ****
dir fsync took 8677 ms after adding 1000000 files (-13.6%)
dir fsync took 146 ms after deleting 1000 files (-105.6%)
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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When logging a directory, we scan its directory items from the subvolume
tree and then copy one by one into the log tree. This is not efficient
since we generally are able to insert several items in a batch, using a
single btree operation for adding several items at once. The reason we
copy items one by one is that we must check if each item was previously
logged in the current transaction, and if it was we either overwrite it
or skip it in case its content did not change in the subvolume tree (this
can happen only for dir item keys, but not for dir index keys), and doing
such check makes it a bit cumbersome to attempt batch insertions.
However the chances for doing batch insertions are very frequent and
always happen when:
1) Logging the directory for the first time in the current transaction,
as none of the items exist in the log tree yet;
2) Logging new dir index keys, because the offset for new dir index keys
comes from a monotonically increasing counter. This means if we keep
adding dentries to a directory, through creation of new files and
sub-directories or by adding new links or renaming from some other
directory into the one we are logging, all the new dir index keys
have a new offset that is greater than the offset of any previously
logged index keys, so we can insert them in batches into the log tree.
For dir item keys, since their offset depends on the result of an hash
function against the dentry's name, unless the directory is being logged
for the first time in the current transaction, the chances being able to
insert the items in the log using batches is pretty much random and not
predictable, as it depends on the names of the dentries, but still happens
often enough.
So change directory logging to keep track of consecutive directory items
that don't exist yet in the log and batch insert them.
This patch is part of a patchset comprised of the following 5 patches:
btrfs: remove root argument from btrfs_log_inode() and its callees
btrfs: remove redundant log root assignment from log_dir_items()
btrfs: factor out the copying loop of dir items from log_dir_items()
btrfs: insert items in batches when logging a directory when possible
btrfs: keep track of the last logged keys when logging a directory
This is patch 4/5. The change log of the last patch (5/5) has performance
results.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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In preparation for the next change, move the loop that processes a leaf
and copies its directory items to the log, into a separate helper
function. This makes the next change simpler and it also helps making
log_dir_items() a bit shorter (specially after the next change).
This patch is part of a patchset comprised of the following 5 patches:
btrfs: remove root argument from btrfs_log_inode() and its callees
btrfs: remove redundant log root assignment from log_dir_items()
btrfs: factor out the copying loop of dir items from log_dir_items()
btrfs: insert items in batches when logging a directory when possible
btrfs: keep track of the last logged keys when logging a directory
This is patch 3/5. The change log of the last patch (5/5) has performance
results.
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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Anand Jain
Nikolay Borisov
Josef Bacik
Kai Song
Qu Wenruo
Filipe Manana
