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[PATCH-v3 3/6] vfs: don't let the dirty time inodes get more than a day

To: Linux Filesystem Development List <linux-fsdevel@xxxxxxxxxxxxxxx>
Subject: [PATCH-v3 3/6] vfs: don't let the dirty time inodes get more than a day stale
From: Theodore Ts'o <tytso@xxxxxxx>
Date: Tue, 25 Nov 2014 00:34:31 -0500
Cc: Ext4 Developers List <linux-ext4@xxxxxxxxxxxxxxx>, Linux btrfs Developers List <linux-btrfs@xxxxxxxxxxxxxxx>, XFS Developers <xfs@xxxxxxxxxxx>, Theodore Ts'o <tytso@xxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
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In-reply-to: <1416893674-419-1-git-send-email-tytso@xxxxxxx>
References: <1416893674-419-1-git-send-email-tytso@xxxxxxx>
Guarantee that the on-disk timestamps will be no more than 24 hours
stale.

Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
---
 fs/fs-writeback.c  |  1 +
 fs/inode.c         | 28 +++++++++++++++++++++++-----
 include/linux/fs.h |  1 +
 3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index ce7de22..eb04277 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1141,6 +1141,7 @@ void __mark_inode_dirty(struct inode *inode, int flags)
        if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
                trace_writeback_dirty_inode_start(inode, flags);
 
+               inode->i_ts_dirty_day = 0;
                if (sb->s_op->dirty_inode)
                        sb->s_op->dirty_inode(inode, flags);
 
diff --git a/fs/inode.c b/fs/inode.c
index 2093a84..34a443f 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1511,6 +1511,8 @@ static int relatime_need_update(struct vfsmount *mnt, 
struct inode *inode,
  */
 static int update_time(struct inode *inode, struct timespec *time, int flags)
 {
+       struct timespec uptime;
+       unsigned short daycode;
        int ret;
 
        if (inode->i_op->update_time) {
@@ -1525,17 +1527,33 @@ static int update_time(struct inode *inode, struct 
timespec *time, int flags)
                if (flags & S_CTIME)
                        inode->i_ctime = *time;
                if (flags & S_MTIME)
-                       inode->i_mtime = *time;
+               inode->i_mtime = *time;
        }
+       /*
+        * If i_ts_dirty_day is zero, then either we have not deferred
+        * timestamp updates, or the system has been up for less than
+        * a day (so days_since_boot is zero), so we defer timestamp
+        * updates in that case and set the I_DIRTY_TIME flag.  If a
+        * day or more has passed, then i_ts_dirty_day will be
+        * different from days_since_boot, and then we should update
+        * the on-disk inode and then we can clear i_ts_dirty_day.
+        */
        if ((inode->i_sb->s_flags & MS_LAZYTIME) &&
            !(flags & S_VERSION)) {
                if (inode->i_state & I_DIRTY_TIME)
                        return 0;
-               spin_lock(&inode->i_lock);
-               inode->i_state |= I_DIRTY_TIME;
-               spin_unlock(&inode->i_lock);
-               return 0;
+               get_monotonic_boottime(&uptime);
+               daycode = div_u64(uptime.tv_sec, (HZ * 86400));
+               if (!inode->i_ts_dirty_day ||
+                   inode->i_ts_dirty_day == daycode) {
+                       spin_lock(&inode->i_lock);
+                       inode->i_state |= I_DIRTY_TIME;
+                       spin_unlock(&inode->i_lock);
+                       inode->i_ts_dirty_day = daycode;
+                       return 0;
+               }
        }
+       inode->i_ts_dirty_day = 0;
        if (inode->i_op->write_time)
                return inode->i_op->write_time(inode);
        mark_inode_dirty_sync(inode);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 489b2f2..e3574cd 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -575,6 +575,7 @@ struct inode {
        struct timespec         i_ctime;
        spinlock_t              i_lock; /* i_blocks, i_bytes, maybe i_size */
        unsigned short          i_bytes;
+       unsigned short          i_ts_dirty_day;
        unsigned int            i_blkbits;
        blkcnt_t                i_blocks;
 
-- 
2.1.0

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