fuse: only refresh size on cached write when opened with O_APPEND - #193
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In fuse_cache_write_iter, writeback_cache mode was always refreshing STATX_SIZE along with STATX_MODE before a buffered write. The size refresh is only needed for the O_APPEND path, where the kernel must know the current EOF before extending the file. For ordinary writes, fetching size is unnecessary work and can race with concurrent writes and then impact writeback performance. Keep refreshing STATX_MODE in all cases so SUID clearing still sees an up-to-date mode. Request STATX_SIZE only when the file is opened with O_APPEND. Signed-off-by Hai Zhong Zhou <hazhou@ddn.com>
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achhenderson,
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cding-ddn,
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yongzech
July 29, 2026 12:04
hbirth
approved these changes
Jul 29, 2026
hbirth
merged commit Jul 29, 2026
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DDNStorage:redfs-ubuntu-hwe-6.17.0-16.16-24.04.1
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In fuse_cache_write_iter, writeback_cache mode was always refreshing STATX_SIZE along with STATX_MODE before a buffered write. The size refresh is only needed for the O_APPEND path, where the kernel must know the current EOF before extending the file. For ordinary writes, fetching size is unnecessary work and can race with concurrent writes and then impact writeback performance.
Keep refreshing STATX_MODE in all cases so SUID clearing still sees an up-to-date mode. Request STATX_SIZE only when the file is opened with O_APPEND.
Signed-off-by Hai Zhong Zhou hazhou@ddn.com