On Thursday, November 30, 2017 12:23:45 AM CET Luis R. Rodriguez wrote: > This is a followup from the original RFC which proposed to start > to kill kthread freezing all together [0]. Instead of going straight > out to the jugular for kthread freezing this series only addresses > killing freezer calls on filesystems which implement freeze_fs, after > we let the kernel freeze these filesystems for us on suspend. > > This approach puts on a slow but steady path towards the original goal > though. Each subsystem could look for similar solutions. Even with > filesystems we're not all done yet, after this we'll still have to > decide what to do about filesystems which do not implement freeze_fs(). > > Motivation and problem: > > kthreads have some semantics for freezing, which helps the kernel > freeze them when a system is going to suspend or hibernation. These > semantics are not well defined though, and it actually turns out > pretty hard to get it right. > > Without a proper solution suspend and hibernation are fragile on filesystems, > it can easily break suspend and fixing such issues are in no way trivial [1] > [2]. > > Proposed solution: > > Instead of fixing such semantics and trying to get all filesystems to do it > right, we can easily do away with all freezing calls if the filesystem > implements a proper freeze_fs() callback. The following 9 filesystems have > freeze_fs() implemented as such we can let the kernel issue the callback upon > suspend and thaw on resume automatically on our behalf. > > o xfs > o reiserfs > o nilfs2 > o jfs > o f2fs > o ext4 > o ext2 > o btrfs > > Of these, the following have freezer helpers, which can then be removed > after the kernel automaticaly calls freeze_fs for us on suspend: > > o xfs > o nilfs2 > o jfs > o f2fs > o ext4 > > I've tested this on a system with ext4 and XFS, and have let 0-day go at > without issues. I have branches availabe for linux-next [3] and Linus' > latest tree [4]. > > Further testing, thoughts, reviews, flames are all equally appreciated. > > [0] https://lkml.kernel.org/r/20171003185313.1017-1-mcgrof@xxxxxxxxxx > [1] https://bugzilla.suse.com/show_bug.cgi?id=1043449 > [2] https://lkml.kernel.org/r/20171113103139.GA18936@xxxxxxxxxxxxxxxxxxxx > [3] https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux-next.git/log/?h=20171129-fs-freeze-cleanup > [4] https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux.git/log/?h=20171129-fs-freeze-cleanup > > Luis R. Rodriguez (11): > fs: provide unlocked helper for freeze_super() > fs: provide unlocked helper thaw_super() > fs: add frozen sb state helpers > fs: distinguish between user initiated freeze and kernel initiated > freeze > fs: add iterate_supers_excl() and iterate_supers_reverse_excl() > fs: freeze on suspend and thaw on resume > xfs: remove not needed freezing calls > ext4: remove not needed freezing calls > f2fs: remove not needed freezing calls > nilfs2: remove not needed freezing calls > jfs: remove not needed freezing calls > > fs/ext4/ext4_jbd2.c | 2 +- > fs/ext4/super.c | 2 - > fs/f2fs/gc.c | 5 +- > fs/f2fs/segment.c | 6 +- > fs/jfs/jfs_logmgr.c | 11 +- > fs/jfs/jfs_txnmgr.c | 31 ++--- > fs/nilfs2/segment.c | 48 ++++---- > fs/super.c | 320 ++++++++++++++++++++++++++++++++++++++++--------- > fs/xfs/xfs_trans.c | 2 +- > fs/xfs/xfs_trans_ail.c | 7 +- > include/linux/fs.h | 63 +++++++++- > kernel/power/process.c | 15 ++- > 12 files changed, 378 insertions(+), 134 deletions(-) > I'm assuming an update of this to be posted due to the comments from Jan on patch [3/11] and patch [7/11] probably. Is there anything else that needs to be addressed? Thanks, Rafael
