Messages in this thread | | | From | Amir Goldstein <> | Date | Thu, 9 Apr 2020 13:23:29 +0300 | Subject | Re: [PATCH] ovl: skip overlayfs superblocks at global sync |
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On Thu, Apr 9, 2020 at 11:30 AM Konstantin Khlebnikov <khlebnikov@yandex-team.ru> wrote: > > Stacked filesystems like overlayfs has no own writeback, but they have to > forward syncfs() requests to backend for keeping data integrity. > > During global sync() each overlayfs instance calls method ->sync_fs() > for backend although it itself is in global list of superblocks too. > As a result one syscall sync() could write one superblock several times > and send multiple disk barriers. > > This patch adds flag SB_I_SKIP_SYNC into sb->sb_iflags to avoid that. > > Reported-by: Dmitry Monakhov <dmtrmonakhov@yandex-team.ru> > Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> > ---
Seems reasonable. You may add: Reviewed-by: Amir Goldstein <amir73il@gmail.com>
+CC: containers list
This bring up old memories. I posted this way back to fix handling of emergency_remount() in the presence of loop mounted fs: https://lore.kernel.org/linux-ext4/CAA2m6vfatWKS1CQFpaRbii2AXiZFvQUjVvYhGxWTSpz+2rxDyg@mail.gmail.com/
But seems to me that emergency_sync() and sync(2) are equally broken for this use case.
I wonder if anyone cares enough about resilience of loop mounted fs to try and change the iterate_* functions to iterate supers/bdevs in reverse order...
Thanks, Amir.
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