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block: Fix elv_iosched_local_module handling of "none" scheduler

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commit e3accac1a976e65491a9b9fba82ce8ddbd3d2389 upstream.

Commit 734e1a8603 ("block: Prevent deadlocks when switching
elevators") introduced the function elv_iosched_load_module() to allow
loading an elevator module outside of elv_iosched_store() with the
target device queue not frozen, to avoid deadlocks. However, the "none"
scheduler does not have a module and as a result,
elv_iosched_load_module() always returns an error when trying to switch
to this valid scheduler.

Fix this by ignoring the return value of the request_module() call
done by elv_iosched_load_module(). This restores the behavior before
commit 734e1a8603, which was to ignore the request_module() result and
instead rely on elevator_change() to handle the "none" scheduler case.

Reported-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Fixes: 734e1a8603 ("block: Prevent deadlocks when switching elevators")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240917133231.134806-1-dlemoal@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Damien Le Moal 2024-09-17 22:32:31 +09:00 committed by Greg Kroah-Hartman
parent cdf27834c3
commit 2327c3f9d4
1 changed files with 3 additions and 1 deletions
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4
block/elevator.c
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@ -715,7 +715,9 @@ int elv_iosched_load_module(struct gendisk *disk, const char *buf,
strscpy(elevator_name, buf, sizeof(elevator_name));
return request_module("%s-iosched", strstrip(elevator_name));
request_module("%s-iosched", strstrip(elevator_name));
return 0;
}
ssize_t elv_iosched_store(struct gendisk *disk, const char *buf,