On 5/21/24 03:21, David Sterba wrote:
On Sat, May 18, 2024 at 05:57:12AM +0800, Anand Jain wrote:
On 5/17/24 06:12, David Sterba wrote:
From: Josef Bacik <josef@xxxxxxxxxxxxxx>
There are some btrfs tests that do _scratch_pool_mkfs in a loop.
Sometimes this fails with EBUSY. Tracing revealed that udevd will
sometimes write to /sys/block/device/uevent to make sure an event
triggers to rules get written. However these events will not get sent
to user space until after an O_EXCL open as been closed. The general
flow is something like
mkfs.btrfs /dev/sda /dev/sdb /dev/sdc /dev/sdd
mount /dev/sda /mnt/test
<things>
umount /mnt/test
in a loop. The problem is udevd will add uevents for the devices and
they won't get delivered until after the umount. If we're doing the
above sequence in a loop the next mkfs.btrfs will fail because udev is
touching the devices to consume the KOBJ_CHANGE event.
Fix this by doing a udev settle before _scratch_pool_mkfs.
Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
---
common/rc | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/common/rc b/common/rc
index 0fe56382a6a497..5d38571ffe87eb 100644
--- a/common/rc
+++ b/common/rc
@@ -903,6 +903,12 @@ _scratch_pool_mkfs()
{
case $FSTYP in
btrfs)
+ # For multi-disk file systems udev can queue up events on the device
+ # when we mkfs the device, and thus tie up the device after we've
+ # unmounted. Tests that _scratch_pool_mkfs() in a loop can sometimes
+ # trip over udev trying to do the updates after the umount, so make sure
+ # we settle before we try mkfs'ing so we don't get an EBUSY
+ $UDEV_SETTLE_PROG >/dev/null 2>&1
$MKFS_BTRFS_PROG $MKFS_OPTIONS $* $SCRATCH_DEV_POOL > /dev/null
;;
Just curious: have we seen this issue even after the btrfs-progs commit
below?
e54514aaeab6 btrfs-progs: fix stray fd close in open_ctree_fs_info()
That's a good question, I don't know but I can revert the change and see
if things break. This may take time as triggering the udev/mkfs race is
not reliable.
Agreed. The udev/mkfs race is tricky and will take a while to report,
but it's good to experiment. IMO.
Thanks! Anand
