On Mon, 2017-12-18 at 17:07 +0100, Jan Kara wrote:

On Mon 18-12-17 10:11:53, Jeff Layton wrote:

quoted

From: Jeff Layton <redacted>

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 <redacted>
---
 fs/inode.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index 03102d6ef044..83f6cfc3cde7 100644
--- a/fs/inode.c
+++ b/fs/inode.c

@@ -19,6 +19,7 @@
 #include <linux/ratelimit.h>
 #include <linux/list_lru.h>
 #include <trace/events/writeback.h>
+#include <linux/iversion.h>
 #include "internal.h"
 
 /*

@@ -1634,17 +1635,24 @@ 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)
+	if (flags & S_ATIME) {
 		inode->i_atime = *time;
+		dirty |= !(inode->i_sb->s_flags & SB_LAZYTIME);
+	}
 	if (flags & S_VERSION)
-		inode_inc_iversion(inode);
-	if (flags & S_CTIME)
+		dirty |= inode_maybe_inc_iversion(inode, dirty);
+	if (flags & S_CTIME) {
 		inode->i_ctime = *time;
-	if (flags & S_MTIME)
+		dirty = true;
+	}
+	if (flags & S_MTIME) {
 		inode->i_mtime = *time;
+		dirty = true;
+	}

The SB_LAZYTIME handling is wrong here. That option is not only about atime
handling but rather about all inode time stamps. So you rather need
something like:

	if (flags & (S_ATIME | S_CTIME | S_MTIME) &&
	    !(inode->i_sb->s_flags & SB_LAZYTIME))
		dirty = true;

								Honza

Thanks. I misunderstood that. Will fix.

quoted

 
-	if (!(inode->i_sb->s_flags & SB_LAZYTIME) || (flags & S_VERSION))
+	if (dirty)
 		iflags |= I_DIRTY_SYNC;
 	__mark_inode_dirty(inode, iflags);
 	return 0;

@@ -1863,7 +1871,7 @@ 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)

-- 
2.14.3

-- 
Jeff Layton [off-list ref]