From: Qu Wenruo <wqu@suse.com>
To: linux-btrfs@vger.kernel.org
Cc: Johannes.Thumshirn@wdc.com, josef@toxicpanda.com
Subject: [PATCH v5 0/5] btrfs: subpage + zoned fixes
Date: Sat, 18 May 2024 14:37:38 +0930 [thread overview]
Message-ID: <cover.1716008374.git.wqu@suse.com> (raw)
[CHANGELOG]
v5:
- Enhance the commit message on why we should not clear page dirty
inside extent_write_locked_range()
- Reorder the patches so that no temporary list based solution for
delalloc ranges
v4:
- Rebased to the latest for-next branch
Thankfully no conflicts at all.
- Include all the previous preparation patches
It turns out I split the preparation into other series and even get
myself confused.
- Use the correct commit message from my local branch
It turns out Josef is totally correct, the problem I described in
"btrfs: do no clera page dirty inside extent_write_locked_range()" is
really confusing, it has direct IO involved and my local branch is
already using a much better commit and I just forgot it.
v3:
- Use the minimal fsstress workload with trace_printk() output to
explain the bug better
v2:
- Update the commit message for the first patch
As there is something wrong with the ASCII art of the memory layout.
[REPO]
https://github.com/adam900710/linux/tree/subpage_delalloc
If running subpage with zoned devices (TCMU emulated HDD, 64K or 16K
page size with 4K sectorsize), btrfs can easily hitting various bugs:
- ASSERT()s related to submitting page range which has no OE coverage
- Various reserved space leakage and some OE never finished
This is caused by two major reasons:
- run_delalloc_cow() is not subpage compatible
There are several different problems involved furthermore.
* extent_write_locked_range() would try to submit dirty pages beyond
the specified subpage range
Thus hit some ASSERT() that a dirty range has no corresponding OE
* extent_write_locked_range() would unlock the whole page meanwhile
we're only triggered for a subpage range
Thus causing unexpected page to be unlocked.
This would be addressed by patch 1~3 by:
* Limited the submission range to follow the subpage ranges
* Make the page unlocking part also subpage compatible, and always
lock all delalloc subpage ranges covering the current page.
- Some dirty range is not submitted thus OE would never finish
This happens due to the mismatch that extent_write_locked_range() can
clear the full page dirty, even if we're only submitting part of the
dirty ranges, causing page dirty flags desync from subpage dirty
flags.
Then later __extent_writepage_io() would skip a non-dirty page, as the
check is only checking the full page dirty flag, not the
subpage bitmaps.
This would be addressed by patch 4~5.
Qu Wenruo (5):
btrfs: make __extent_writepage_io() to write specified range only
btrfs: subpage: introduce helpers to handle subpage delalloc locking
btrfs: lock subpage ranges in one go for writepage_delalloc()
btrfs: do not clear page dirty inside extent_write_locked_range()
btrfs: make extent_write_locked_range() to handle subpage writeback
correctly
fs/btrfs/extent_io.c | 105 +++++++++++++++++++++++++------
fs/btrfs/subpage.c | 144 +++++++++++++++++++++++++++++++++++++++++--
fs/btrfs/subpage.h | 10 ++-
3 files changed, 233 insertions(+), 26 deletions(-)
--
2.45.0
next reply other threads:[~2024-05-18 5:08 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-18 5:07 Qu Wenruo [this message]
2024-05-18 5:07 ` [PATCH v5 1/5] btrfs: make __extent_writepage_io() to write specified range only Qu Wenruo
2024-05-21 7:23 ` Naohiro Aota
2024-05-18 5:07 ` [PATCH v5 2/5] btrfs: subpage: introduce helpers to handle subpage delalloc locking Qu Wenruo
2024-05-21 7:50 ` Naohiro Aota
2024-05-21 7:57 ` Qu Wenruo
2024-05-18 5:07 ` [PATCH v5 3/5] btrfs: lock subpage ranges in one go for writepage_delalloc() Qu Wenruo
2024-05-21 8:11 ` Naohiro Aota
2024-05-21 8:45 ` Qu Wenruo
2024-05-21 11:54 ` Naohiro Aota
2024-05-21 22:16 ` Qu Wenruo
2024-05-22 1:10 ` Naohiro Aota
2024-05-18 5:07 ` [PATCH v5 4/5] btrfs: do not clear page dirty inside extent_write_locked_range() Qu Wenruo
2024-05-18 5:07 ` [PATCH v5 5/5] btrfs: make extent_write_locked_range() to handle subpage writeback correctly Qu Wenruo
2024-05-21 7:13 ` Naohiro Aota
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