On 01/16/2018 03:26 AM, David Sterba wrote:
On Fri, Jan 12, 2018 at 06:14:40PM +0800, Anand Jain wrote:Misono, This change is causing subsequent (subvol) mount to fail when device option is specified. The simplest eg for failure is .. mkfs.btrfs -qf /dev/sdc /dev/sdb mount -o device=/dev/sdb /dev/sdc /btrfs mount -o device=/dev/sdb /dev/sdc /btrfs1 mount: /dev/sdc is already mounted or /btrfs1 busy Looks like blkdev_get_by_path() <-- is failing. btrfs_scan_one_device() btrfs_parse_early_options() btrfs_mount() Which is due to different holders (viz. btrfs_root_fs_type and btrfs_fs_type) one is used for vfs_mount and other for scan, so they form different holders and can't let EXCL open which is needed for both scan and open.This looks close to what I see in the random test failures. I've reverted your patch "btrfs: optimize move uuid_mutex closer to the critical section" as I bisected to it. The uuid mutex around blkdev_get_path probably protected the concurrent mount and scan so they did not ask for EXCL at the same time. Reverting (or removing the patch from the current misc-next) queue is simpler for me ATM as I want to get to a stable base now, we can add it later if we understand the issue with the mount/scan.
Right. I don't see above test case failing on your branch [1] which does not have the uuid_mutex patch. Quite strange, there isn't any concurrency (mount and scan) in this test case. [1] git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git for-next Ran xfstests, got stuck at btrfs/011 failures, (and will wait for Liubo's v2 patch). OR is there any other test case you were referring to as random test failures ? Thanks, Anand
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