On 03/03, Jaegeuk Kim wrote: > On 03/04, Dave Chinner wrote: > > On Thu, Mar 03, 2022 at 06:21:04PM -0800, Jaegeuk Kim wrote: > > > Otherwise, we will get a deadlock. > > > > NACK. > > > > We have to be able to evict clean inodes from memory on frozen > > inodes because we can still instantiate inodes while the filesytem > > is frozen. e.g. there's a find running when the filesystem is > > frozen. What happens if we can't evict clean cached inodes from > > memory when we run out of memory trying to instantiate new inodes? > > Ok, that makes sense. > > > > > > > > > [freeze test] shrinkder > > > freeze_super > > > - pwercpu_down_write(SB_FREEZE_FS) > > > - super_cache_scan > > > - down_read(&sb->s_umount) > > > - prune_icache_sb > > > - dispose_list > > > - evict > > > - f2fs_evict_inode > > > thaw_super > > > - down_write(&sb->s_umount); > > > - __percpu_down_read(SB_FREEZE_FS) > > > > That seems like a f2fs bug, not a generic problem. > > > > Filesystems already have to handle stuff like this if an unlinked > > file is closed while the fs is frozen - we have to handle inode > > eviction needing to modify the file, and different filesystems > > handle this differently. Most filesystems simply block in > > ->evict_inode in this case, but this never occurs from the shrinker > > context. > > > > IOWs, the shrinker should never be evicting inodes that require the > > filesystem to immediately block on frozen filesystems. If you have > > such inodes in cache at the time the filesystem is frozen, then they > > should be purged from the cache as part of the freeze process so the > > shrinker won't ever find inodes that it could deadlock on. > > If so, is this a bug in drop_caches_sysctl_handler? Or, I shouldn't have > used "echo 3 > sysfs/drop_caches" with freezefs in xfstests? My bad. I totally misunderstood. I'm testing a patch to call evict_inodes() in f2fs_freeze(). Thank you for the comment. :) > > > > > Cheers, > > > > Dave. > > -- > > Dave Chinner > > david@xxxxxxxxxxxxx
