Fix corruption caused by mmap flushing problems #16019
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1) Make mmap flushes synchronous. Linux may skip flushing dirty pages already in writeback unless data-integrity sync is requested. 2) Change zfs_putpage to use TXG_WAIT. Otherwise dirty pages may be skipped due to DMU pushing back on TX assign. 3) Add missing mmap flush when doing block cloning. 4) While here, pass errors from putpage to writepage/writepages. This change fixes corruption edge cases, but unfortunately adds synchronous ZIL flushes for dirty mmap pages to llseek and bclone operations. It may be possible to avoid these sync writes later but would need more tricky refactoring of the writeback code. Fixes: openzfs#15933 Signed-off-by: Robert Evans <evansr@google.com>
amotin
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Mar 22, 2024
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behlendorf
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Mar 22, 2024
behlendorf
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Mar 22, 2024
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Will it be cherry-picked to v2.2.4 ? |
rrevans
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Mar 28, 2024
1) Make mmap flushes synchronous. Linux may skip flushing dirty pages already in writeback unless data-integrity sync is requested. 2) Change zfs_putpage to use TXG_WAIT. Otherwise dirty pages may be skipped due to DMU pushing back on TX assign. 3) Add missing mmap flush when doing block cloning. 4) While here, pass errors from putpage to writepage/writepages. This change fixes corruption edge cases, but unfortunately adds synchronous ZIL flushes for dirty mmap pages to llseek and bclone operations. It may be possible to avoid these sync writes later but would need more tricky refactoring of the writeback code. Reviewed-by: Alexander Motin <mav@FreeBSD.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Robert Evans <evansr@google.com> Closes openzfs#15933 Closes openzfs#16019
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@ssergiienko yes it will - I just opened a backport PR (#16039) so it doesn't get forgotten. |
behlendorf
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Mar 30, 2024
1) Make mmap flushes synchronous. Linux may skip flushing dirty pages already in writeback unless data-integrity sync is requested. 2) Change zfs_putpage to use TXG_WAIT. Otherwise dirty pages may be skipped due to DMU pushing back on TX assign. 3) Add missing mmap flush when doing block cloning. 4) While here, pass errors from putpage to writepage/writepages. This change fixes corruption edge cases, but unfortunately adds synchronous ZIL flushes for dirty mmap pages to llseek and bclone operations. It may be possible to avoid these sync writes later but would need more tricky refactoring of the writeback code. Reviewed-by: Alexander Motin <mav@FreeBSD.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Robert Evans <evansr@google.com> Closes #15933 Closes #16019
lundman
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Sep 4, 2024
1) Make mmap flushes synchronous. Linux may skip flushing dirty pages already in writeback unless data-integrity sync is requested. 2) Change zfs_putpage to use TXG_WAIT. Otherwise dirty pages may be skipped due to DMU pushing back on TX assign. 3) Add missing mmap flush when doing block cloning. 4) While here, pass errors from putpage to writepage/writepages. This change fixes corruption edge cases, but unfortunately adds synchronous ZIL flushes for dirty mmap pages to llseek and bclone operations. It may be possible to avoid these sync writes later but would need more tricky refactoring of the writeback code. Reviewed-by: Alexander Motin <mav@FreeBSD.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Robert Evans <evansr@google.com> Closes openzfs#15933 Closes openzfs#16019
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Motivation and Context
See #15933
TL;DR there are three separate bugs underlying that issue which are addressed by this PR. See the description below.
Description
Make mmap flushes synchronous. Linux may skip flushing dirty pages
already in writeback unless data-integrity sync is requested.
Change zfs_putpage to use TXG_WAIT. Otherwise dirty pages may be
skipped due to DMU pushing back on TX assign.
Add missing mmap flush when doing block cloning.
While here, pass errors from putpage to writepage/writepages.
This change fixes corruption edge cases, but unfortunately adds synchronous ZIL flushes for dirty mmap pages to llseek and bclone operations. It may be possible to avoid these sync writes later but would need more tricky refactoring of the writeback code.
How Has This Been Tested?
Both the reproducer from #15933 and gentoo emerge test script pass after multiple hours.
Types of changes
Checklist:
Signed-off-by.