[PATCH 0/4] add support for a lazytime mount option

Theodore Ts'o
2014-11-21T19:59:46Z

This is an updated version of what had originally been an
ext4-specific patch which significantly improves performance by lazily
writing timestamp updates (and in particular, mtime updates) to disk.
The in-memory timestamps are always correct, but they are only written
to disk when required for correctness.

This provides a huge performance boost for ext4 due to how it handles
journalling, but it's valuable for all file systems running on flash
storage or drive-managed SMR disks by reducing the metadata write
load. So upon request, I've moved the functionality to the VFS layer.
Once the /sbin/mount program adds support for MS_LAZYTIME, all file
systems should be able to benefit from this optimization.

There is still an ext4-specific optimization, which may be applicable
for other file systems which store more than one inode in a block, but
it will require file system specific code. It is purely optional,
however.

Please note the changes to update_time() and the new write_time() inode
operations functions, which impact btrfs and xfs. The changes are
fairly simple, but I would appreciate confirmation from the btrfs and
xfs teams that I got things right. Thanks!!

Theodore Ts'o (4):
fs: split update_time() into update_time() and write_time()
vfs: add support for a lazytime mount option
vfs: don't let the dirty time inodes get more than a day stale
ext4: add support for a lazytime mount option

fs/btrfs/inode.c | 10 ++++++
fs/ext4/inode.c | 46 +++++++++++++++++++++++++-
fs/ext4/super.c | 9 +++++
fs/fs-writeback.c | 39 +++++++++++++++++++++-
fs/inode.c | 88 ++++++++++++++++++++++++++++++++++++++++++-------
fs/proc_namespace.c | 1 +
fs/sync.c | 7 ++++
fs/xfs/xfs_iops.c | 39 +++++++++-------------
include/linux/fs.h | 5 +++
include/uapi/linux/fs.h | 1 +
10 files changed, 209 insertions(+), 36 deletions(-)

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2.1.0