[lustre-devel] [PATCH 15/40] lustre: llite: fix relatime support

[James Simmons <jsimmons@infradead.org>]

From: Aurelien Degremont <degremoa@amazon.com>

relatime behavior is properly managed by VFS, however
Lustre also stores acmtime on OST objects and atime
updates for OST objects should honor relatime behavior.

This patch updates 'ci_noatime' feature which was introduced to
properly honor noatime option for OST objects, to also support
'relatime'.
file_is_noatime() code already comes from upstream touch_atime().
Add missing parts from touch_atime() to also support relatime.

It also forces atime to disk on MDD if ondisk atime is older than
ondisk mtime/ctime to match relatime (even if relatime is not enabled)

WC-bug-id: https://jira.whamcloud.com/browse/LU-15728
Lustre-commit: c10c6eeb37dd55316 ("LU-15728 llite: fix relatime support")
Signed-off-by: Aurelien Degremont <degremoa@amazon.com>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/47017
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Yang Sheng <ys@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
---
 fs/lustre/llite/file.c | 45 ++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 42 insertions(+), 3 deletions(-)

diff --git a/fs/lustre/llite/file.c b/fs/lustre/llite/file.c
index 668d544..18f3302 100644
--- a/fs/lustre/llite/file.c
+++ b/fs/lustre/llite/file.c
@@ -1541,12 +1541,46 @@ void ll_io_set_mirror(struct cl_io *io, const struct file *file)
 	       file->f_path.dentry->d_name.name, io->ci_designated_mirror);
 }
 
+/*
+ * This is relatime_need_update() from Linux 5.17, which is not exported.
+ */
+static int relatime_need_update(struct vfsmount *mnt, struct inode *inode,
+				struct timespec64 now)
+{
+	if (!(mnt->mnt_flags & MNT_RELATIME))
+		return 1;
+	/*
+	 * Is mtime younger than atime? If yes, update atime:
+	 */
+	if (timespec64_compare(&inode->i_mtime, &inode->i_atime) >= 0)
+		return 1;
+	/*
+	 * Is ctime younger than atime? If yes, update atime:
+	 */
+	if (timespec64_compare(&inode->i_ctime, &inode->i_atime) >= 0)
+		return 1;
+
+	/*
+	 * Is the previous atime value older than a day? If yes,
+	 * update atime:
+	 */
+	if ((long)(now.tv_sec - inode->i_atime.tv_sec) >= 24*60*60)
+		return 1;
+	/*
+	 * Good, we can skip the atime update:
+	 */
+	return 0;
+}
+
+/*
+ * Very similar to kernel function: !__atime_needs_update()
+ */
 static bool file_is_noatime(const struct file *file)
 {
-	const struct vfsmount *mnt = file->f_path.mnt;
-	const struct inode *inode = file_inode(file);
+	struct vfsmount *mnt = file->f_path.mnt;
+	struct inode *inode = file_inode(file);
+	struct timespec64 now;
 
-	/* Adapted from file_accessed() and touch_atime().*/
 	if (file->f_flags & O_NOATIME)
 		return true;
 
@@ -1565,6 +1599,11 @@ static bool file_is_noatime(const struct file *file)
 	if ((inode->i_sb->s_flags & SB_NODIRATIME) && S_ISDIR(inode->i_mode))
 		return true;
 
+	now = current_time(inode);
+
+	if (!relatime_need_update(mnt, inode, now))
+		return true;
+
 	return false;
 }
 
-- 
1.8.3.1

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