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authorQu Wenruo <wqu@suse.com>2024-09-16 08:12:40 +0930
committerDavid Sterba <dsterba@suse.com>2024-11-11 14:34:13 +0100
commitc96d0e3921419bd3e5d8a1f355970c8ae3047ef4 (patch)
tree4f4deb50f1b87e6ffeb8c70da9eac976e156b52a /tools/perf/scripts/python/export-to-postgresql.py
parent2bca8eb0774d271b1077b72f1be135073e0a898f (diff)
btrfs: mark all dirty sectors as locked inside writepage_delalloc()
Currently we only mark sectors as locked if there is a *NEW* delalloc range for it. But NEW delalloc range is not the same as dirty sectors we want to submit, e.g: 0 32K 64K 96K 128K | |////////||///////| |////| 120K For above 64K page size case, writepage_delalloc() for page 0 will find and lock the delalloc range [32K, 96K), which is beyond the page boundary. Then when writepage_delalloc() is called for the page 64K, since [64K, 96K) is already locked, only [120K, 128K) will be locked. This means, although range [64K, 96K) is dirty and will be submitted later by extent_writepage_io(), it will not be marked as locked. This is fine for now, as we call btrfs_folio_end_writer_lock_bitmap() to free every non-compressed sector, and compression is only allowed for full page range. But this is not safe for future sector perfect compression support, as this can lead to double folio unlock: Thread A | Thread B ---------------------------------------+-------------------------------- | submit_one_async_extent() | |- extent_clear_unlock_delalloc() extent_writepage() | |- btrfs_folio_end_writer_lock() |- btrfs_folio_end_writer_lock_bitmap()| |- btrfs_subpage_end_and_test_writer() | | | |- atomic_sub_and_test() | | | /* Now the atomic value is 0 */ |- if (atomic_read() == 0) | | |- folio_unlock() | |- folio_unlock() The root cause is the above range [64K, 96K) is dirtied and should also be locked but it isn't. So to make everything more consistent and prepare for the incoming sector perfect compression, mark all dirty sectors as locked. Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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