| Message ID | 20230725-mgctime-v6-0-a794c2b7abca@kernel.org |
|---|---|
| Headers | show |
| Series | fs: implement multigrain timestamps | expand |
On Tue, 25 Jul 2023 10:58:13 -0400, Jeff Layton wrote: > The VFS always uses coarse-grained timestamps when updating the > ctime and mtime after a change. This has the benefit of allowing > filesystems to optimize away a lot metadata updates, down to around 1 > per jiffy, even when a file is under heavy writes. > > Unfortunately, this coarseness has always been an issue when we're > exporting via NFSv3, which relies on timestamps to validate caches. A > lot of changes can happen in a jiffy, so timestamps aren't sufficient to > help the client decide to invalidate the cache. > > [...] Survives xfstests (tmpfs, ext4, overlayfs) and the fs portions of LTP. Let's keep our eyes open for any potential issues. Past suspects has been IMA interacting with overlayfs. We'll see. Picked everything minus the tmpfs-writepage patch that was contentious. --- Applied to the vfs.ctime branch of the vfs/vfs.git tree. Patches in the vfs.ctime branch should appear in linux-next soon. Please report any outstanding bugs that were missed during review in a new review to the original patch series allowing us to drop it. It's encouraged to provide Acked-bys and Reviewed-bys even though the patch has now been applied. If possible patch trailers will be updated. Note that commit hashes shown below are subject to change due to rebase, trailer updates or similar. If in doubt, please check the listed branch. tree: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git branch: vfs.ctime [1/7] fs: pass the request_mask to generic_fillattr https://git.kernel.org/vfs/vfs/c/0a6ab6dc6958 [2/7] fs: add infrastructure for multigrain timestamps https://git.kernel.org/vfs/vfs/c/d242b98ac3e9 [4/7] tmpfs: add support for multigrain timestamps https://git.kernel.org/vfs/vfs/c/1f31c58cf032 [5/7] xfs: switch to multigrain timestamps https://git.kernel.org/vfs/vfs/c/859dd91017dd [6/7] ext4: switch to multigrain timestamps https://git.kernel.org/vfs/vfs/c/093af249eab4 [7/7] btrfs: convert to multigrain timestamps https://git.kernel.org/vfs/vfs/c/b90a04d1c30c
The VFS always uses coarse-grained timestamps when updating the ctime and mtime after a change. This has the benefit of allowing filesystems to optimize away a lot metadata updates, down to around 1 per jiffy, even when a file is under heavy writes. Unfortunately, this coarseness has always been an issue when we're exporting via NFSv3, which relies on timestamps to validate caches. A lot of changes can happen in a jiffy, so timestamps aren't sufficient to help the client decide to invalidate the cache. Even with NFSv4, a lot of exported filesystems don't properly support a change attribute and are subject to the same problems with timestamp granularity. Other applications have similar issues with timestamps (e.g backup applications). If we were to always use fine-grained timestamps, that would improve the situation, but that becomes rather expensive, as the underlying filesystem would have to log a lot more metadata updates. What we need is a way to only use fine-grained timestamps when they are being actively queried. The idea is to use an unused bit in the ctime's tv_nsec field to mark when the mtime or ctime has been queried via getattr. Once that has been marked, the next m/ctime update will use a fine-grained timestamp. This patch series is based on top of Christian's vfs.all branch, which has the recent conversion to the new ctime accessors. It should apply cleanly on top of linux-next. The first two patches should probably go in via the vfs tree. Should the fs-specific patches go in that way as well, or should they go via maintainer trees? Either should be fine. The first two patches should probably go in via Christian's vfs tree. The rest could go via maintainer trees or the vfs tree. For now, I'd like to get these into linux-next. Christian, would you be willing to pick these up for now? Alternately, I can feed them there via the iversion branch that Stephen is already pulling in from my tree. Signed-off-by: Jeff Layton <jlayton@kernel.org> base-commit: cf22d118b89a09a0160586412160d89098f7c4c7 --- Changes in v6: - drop the patch that removed XFS_ICHGTIME_CHG - change WARN_ON_ONCE to ASSERT in xfs conversion patch --- Jeff Layton (7): fs: pass the request_mask to generic_fillattr fs: add infrastructure for multigrain timestamps tmpfs: bump the mtime/ctime/iversion when page becomes writeable tmpfs: add support for multigrain timestamps xfs: switch to multigrain timestamps ext4: switch to multigrain timestamps btrfs: convert to multigrain timestamps fs/9p/vfs_inode.c | 4 +- fs/9p/vfs_inode_dotl.c | 4 +- fs/afs/inode.c | 2 +- fs/btrfs/file.c | 24 ++-------- fs/btrfs/inode.c | 2 +- fs/btrfs/super.c | 5 ++- fs/ceph/inode.c | 2 +- fs/coda/inode.c | 3 +- fs/ecryptfs/inode.c | 5 ++- fs/erofs/inode.c | 2 +- fs/exfat/file.c | 2 +- fs/ext2/inode.c | 2 +- fs/ext4/inode.c | 2 +- fs/ext4/super.c | 2 +- fs/f2fs/file.c | 2 +- fs/fat/file.c | 2 +- fs/fuse/dir.c | 2 +- fs/gfs2/inode.c | 2 +- fs/hfsplus/inode.c | 2 +- fs/inode.c | 98 +++++++++++++++++++++++++++++------------ fs/kernfs/inode.c | 2 +- fs/libfs.c | 4 +- fs/minix/inode.c | 2 +- fs/nfs/inode.c | 2 +- fs/nfs/namespace.c | 3 +- fs/ntfs3/file.c | 2 +- fs/ocfs2/file.c | 2 +- fs/orangefs/inode.c | 2 +- fs/proc/base.c | 4 +- fs/proc/fd.c | 2 +- fs/proc/generic.c | 2 +- fs/proc/proc_net.c | 2 +- fs/proc/proc_sysctl.c | 2 +- fs/proc/root.c | 3 +- fs/smb/client/inode.c | 2 +- fs/smb/server/smb2pdu.c | 22 ++++----- fs/smb/server/vfs.c | 3 +- fs/stat.c | 59 ++++++++++++++++++++----- fs/sysv/itree.c | 3 +- fs/ubifs/dir.c | 2 +- fs/udf/symlink.c | 2 +- fs/vboxsf/utils.c | 2 +- fs/xfs/libxfs/xfs_trans_inode.c | 6 +-- fs/xfs/xfs_iops.c | 4 +- fs/xfs/xfs_super.c | 2 +- include/linux/fs.h | 47 ++++++++++++++++++-- mm/shmem.c | 16 ++++++- 47 files changed, 248 insertions(+), 125 deletions(-) --- base-commit: 810b5fff7917119ea82ff96e312e2d4350d6b681 change-id: 20230713-mgctime-f2a9fc324918 Best regards,