From: Alyssa Ross hi@alyssa.is
[ Upstream commit bb430b69422640891b0b8db762885730579a4145 ]
LOOP_CONFIGURE is, as far as I understand it, supposed to be a way to combine LOOP_SET_FD and LOOP_SET_STATUS64 into a single syscall. When using LOOP_SET_FD+LOOP_SET_STATUS64, a single uevent would be sent for each partition found on the loop device after the second ioctl(), but when using LOOP_CONFIGURE, no such uevent was being sent.
In the old setup, uevents are disabled for LOOP_SET_FD, but not for LOOP_SET_STATUS64. This makes sense, as it prevents uevents being sent for a partially configured device during LOOP_SET_FD - they're only sent at the end of LOOP_SET_STATUS64. But for LOOP_CONFIGURE, uevents were disabled for the entire operation, so that final notification was never issued. To fix this, reduce the critical section to exclude the loop_reread_partitions() call, which causes the uevents to be issued, to after uevents are re-enabled, matching the behaviour of the LOOP_SET_FD+LOOP_SET_STATUS64 combination.
I noticed this because Busybox's losetup program recently changed from using LOOP_SET_FD+LOOP_SET_STATUS64 to LOOP_CONFIGURE, and this broke my setup, for which I want a notification from the kernel any time a new partition becomes available.
Signed-off-by: Alyssa Ross hi@alyssa.is [hch: reduced the critical section] Signed-off-by: Christoph Hellwig hch@lst.de Fixes: 3448914e8cc5 ("loop: Add LOOP_CONFIGURE ioctl") Link: https://lore.kernel.org/r/20230320125430.55367-1-hch@lst.de Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/block/loop.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 793ae876918ce..426d0b42685a0 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1010,9 +1010,6 @@ static int loop_configure(struct loop_device *lo, fmode_t mode, /* This is safe, since we have a reference from open(). */ __module_get(THIS_MODULE);
- /* suppress uevents while reconfiguring the device */ - dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 1); - /* * If we don't hold exclusive handle for the device, upgrade to it * here to avoid changing device under exclusive owner. @@ -1067,6 +1064,9 @@ static int loop_configure(struct loop_device *lo, fmode_t mode, } }
+ /* suppress uevents while reconfiguring the device */ + dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 1); + disk_force_media_change(lo->lo_disk, DISK_EVENT_MEDIA_CHANGE); set_disk_ro(lo->lo_disk, (lo->lo_flags & LO_FLAGS_READ_ONLY) != 0);
@@ -1109,17 +1109,17 @@ static int loop_configure(struct loop_device *lo, fmode_t mode, if (partscan) clear_bit(GD_SUPPRESS_PART_SCAN, &lo->lo_disk->state);
+ /* enable and uncork uevent now that we are done */ + dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 0); + loop_global_unlock(lo, is_loop); if (partscan) loop_reread_partitions(lo); + if (!(mode & FMODE_EXCL)) bd_abort_claiming(bdev, loop_configure);
- error = 0; -done: - /* enable and uncork uevent now that we are done */ - dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 0); - return error; + return 0;
out_unlock: loop_global_unlock(lo, is_loop); @@ -1130,7 +1130,7 @@ static int loop_configure(struct loop_device *lo, fmode_t mode, fput(file); /* This is safe: open() is still holding a reference. */ module_put(THIS_MODULE); - goto done; + return error; }
static void __loop_clr_fd(struct loop_device *lo, bool release)