fuse: Fix EIO for writeback when DLM returns -EAGAIN#148
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Fix a logical error where the DLM lock was acquired regardless of whether the writeback part was actually called. This is necessarry after the move to iomap_file_buffered_write() Signed-off-by: Horst Birthelmer <hbirthelmer@ddn.com>
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fs/fuse/file.c.rej should not been added into the commit
The comment is incorrect to me.
We should not return EAGAIN to user space, but when the write return, it releases folio lock, why will it be an ABBA deadlock ?
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fuse_do_readfolio() is called by fuse_iomap_read_folio_range() as well and is not supposed to return a positive value, thus the translation has to be done in another layer. Signed-off-by: Horst Birthelmer <hbirthelmer@ddn.com>
When FUSE server returns -EAGAIN during iomap write operations due to DLM lock contention, a deadlock can occur: 1. iomap write path holds folio lock and calls fuse_iomap_read_folio_range() 2. FUSE gets -EAGAIN from server (DLM lock conflict with page invalidation) 3. fuse_do_readfolio() converts -EAGAIN to AOP_TRUNCATED_PAGE 4. iomap doesn't understand AOP_TRUNCATED_PAGE and fails the write 5. Meanwhile page invalidation holds DLM lock and waits for folio lock 6. Result: ABBA deadlock This is a FUSE-only workaround until mainline iomap gains AOP_TRUNCATED_PAGE retry support. The solution: 1. Add per-task retry tracking in fuse_conn using xarray 2. When fuse_iomap_read_folio_range() sees AOP_TRUNCATED_PAGE: - Create retry entry for current task - Convert to -EAGAIN for iomap 3. In fuse_cache_write_iter(), after iomap returns error: - Check if retry entry exists for current task - If yes, erase it and retry the entire write operation This breaks the deadlock by allowing the folio lock to be released (per AOP_TRUNCATED_PAGE contract) and retrying at a higher level. Signed-off-by: Bernd Schubert <bernd@bsbernd.com>
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yes I noticed ;-) |
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These are some small improvements that are only valid for kernel 6.17