fuse: fix io-uring background queue dispatch on request completion

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When a background request completes via the io_uring path, the
background queue gets flushed to dispatch pending background requests,
but this is done before the connection-level background counters
(fc->num_background, fc->active_background) are properly accounted,
which may reduce effective queue depth to one.

The connection-level counters are decremented in fuse_request_end(), but
flush_bg_queue() flushes the /dev/fuse path queue (fc->bg_queue), not
the io_uring per-queue bg one, which means pending uring background
requests on the queue are never dispatched in this path.

Fix this by accounting the connection-level background counters first
before flushing the queue's background queue. Since
fuse_request_bg_finish() clears FR_BACKGROUND, fuse_request_end() will
skip the background cleanup branch entirely, which avoids any
double-decrements; it will call the wake_up(&req->waitq) branch but this
is effectively a no-op as background requests have no waiters on
req->waitq.

Reviewed-by: Bernd Schubert <bernd@bsbernd.com>
Fixes: 857b0263f3 ("fuse: Allow to queue bg requests through io-uring")
Cc: stable@vger.kernel.org
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

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This commit is contained in:

Joanne Koong 2026-04-08 10:25:10 -07:00 • committed by Miklos Szeredi

parent 9fa4f7a534

commit 31da059891

3 changed files with 26 additions and 17 deletions

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41

fs/fuse/dev.c

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1

fs/fuse/dev_uring.c

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1

fs/fuse/fuse_dev_i.h

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