fuse: avoid tmp copying of data for writeback cached data #9
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bsbernd
approved these changes
Jul 10, 2025
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We need to test this severely through xfstests. @hbirth I think there are missing flags for the mm system that we cannot backport - could add in the commit message which parts you couldn't backport and also add a link to the patch you took the main changes from?
I do xfstests ATM. With KASAN it takes a very long time ... so I will do with and without to save some time. Will do the documentation after some of the testing. |
generic/488 fails with fuse2fs in the following fashion: generic/488 _check_generic_filesystem: filesystem on /dev/sdf is inconsistent (see /var/tmp/fstests/generic/488.full for details) This test opens a large number of files, unlinks them (which really just renames them to fuse hidden files), closes the program, unmounts the filesystem, and runs fsck to check that there aren't any inconsistencies in the filesystem. Unfortunately, the 488.full file shows that there are a lot of hidden files left over in the filesystem, with incorrect link counts. Tracing fuse_request_* shows that there are a large number of FUSE_RELEASE commands that are queued up on behalf of the unlinked files at the time that fuse_conn_destroy calls fuse_abort_conn. Had the connection not aborted, the fuse server would have responded to the RELEASE commands by removing the hidden files; instead they stick around. Create a function to push all the background requests to the queue and then wait for the number of pending events to hit zero, and call this before fuse_abort_conn. That way, all the pending events are processed by the fuse server and we don't end up with a corrupt filesystem. Signed-off-by: Darrick J. Wong <[email protected]>
This is a preparation to allow fuse-io-uring bg queue flush from flush_bg_queue() This does two function renames: fuse_uring_flush_bg -> fuse_uring_flush_queue_bg fuse_uring_abort_end_requests -> fuse_uring_flush_bg And fuse_uring_abort_end_queue_requests() is moved to fuse_uring_stop_queues(). Signed-off-by: Bernd Schubert <[email protected]>
This is useful to have a unique API to flush background requests. For example when the bg queue gets flushed before the remaining of fuse_conn_destroy(). Signed-off-by: Bernd Schubert <[email protected]>
When writing back pages while using writeback caching the code did a copy of data into temporary pages to avoid a deadlock in reclaiming of memory. This is an adaptation and backport of a patch by Joanne Koong [email protected]. Since we use pinned memory with io_uring we don't need the temporary copies and we don't use the AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM flag in the pagemap. Link: https://www.spinics.net/lists/linux-mm/msg407405.html Signed-off-by: Horst Birthelmer <[email protected]>
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When calling the fuse server with a dlm request and the fuse server responds with some other error than ENOSYS most likely the lock size will be set to zero. In that case the kernel will abort the fuse connection. This is completely unnecessary. Signed-off-by: Horst Birthelmer <[email protected]>
Check whether dlm is still enabled when interpreting the returned error from fuse server. Signed-off-by: Horst Birthelmer <[email protected]>
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The patch fuse: fix connection abort on mmap when fuse server returns ENOSYS looks good, thanks for catching this issue. |
bsbernd
approved these changes
Jul 21, 2025
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When writing back pages while using writeback caching the code did a copy of data into temporary pages to avoid a deadlock in reclaiming of memory.
Since we use pinned memory with io_uring we don't need the temporary copies.