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fs/buffer: serialize set_buffer_uptodate against concurrent clears #1305

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fs/buffer: serialize set_buffer_uptodate against concurrent clears #1305

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14 changes: 14 additions & 0 deletions fs/buffer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2211,8 +2211,22 @@ void block_commit_write(struct folio *folio, size_t from, size_t to)
if (!buffer_uptodate(bh))
partial = true;
} else {
/*
* Per the contract documented at set_buffer_uptodate()
* in include/linux/buffer_head.h, callers must hold
* BH_Lock to serialize against concurrent clears of
* BH_Uptodate. Holding only the folio lock is not
* sufficient: a concurrent end_buffer_write_sync() on
* the write-error path clears BH_Uptodate while
* holding BH_Lock; without BH_Lock here the clear can
* land between set_buffer_uptodate() and
* mark_buffer_dirty(), tripping the WARN_ON_ONCE in
* mark_buffer_dirty().
*/
lock_buffer(bh);
set_buffer_uptodate(bh);
mark_buffer_dirty(bh);
unlock_buffer(bh);
}
if (buffer_new(bh))
clear_buffer_new(bh);
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