fs: only set S_VERSION when updating times if necessary

We only really need to update i_version if someone has queried for it
since we last incremented it. By doing that, we can avoid having to
update the inode if the times haven't changed.

If the times have changed, then we go ahead and forcibly increment the
counter, under the assumption that we'll be going to the storage
anyway, and the increment itself is relatively cheap.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>

diff --git a/fs/inode.c b/fs/inode.c
index 19e72f500f71c81b090fb707d351ede501622e5e..e2ca0f4b5151b243d3f4dab25ec3c130990fa407 100644 (file)
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1635,17 +1635,21 @@ static int relatime_need_update(const struct path *path, struct inode *inode,
 int generic_update_time(struct inode *inode, struct timespec *time, int flags)
 {
        int iflags = I_DIRTY_TIME;
+       bool dirty = false;
 
        if (flags & S_ATIME)
                inode->i_atime = *time;
        if (flags & S_VERSION)
-               inode_inc_iversion(inode);
+               dirty = inode_maybe_inc_iversion(inode, false);
        if (flags & S_CTIME)
                inode->i_ctime = *time;
        if (flags & S_MTIME)
                inode->i_mtime = *time;
+       if ((flags & (S_ATIME | S_CTIME | S_MTIME)) &&
+           !(inode->i_sb->s_flags & SB_LAZYTIME))
+               dirty = true;
 
-       if (!(inode->i_sb->s_flags & SB_LAZYTIME) || (flags & S_VERSION))
+       if (dirty)
                iflags |= I_DIRTY_SYNC;
        __mark_inode_dirty(inode, iflags);
        return 0;
@@ -1864,7 +1868,7 @@ int file_update_time(struct file *file)
        if (!timespec_equal(&inode->i_ctime, &now))
                sync_it |= S_CTIME;
 
-       if (IS_I_VERSION(inode))
+       if (IS_I_VERSION(inode) && inode_iversion_need_inc(inode))
                sync_it |= S_VERSION;
 
        if (!sync_it)