[PATCH-v4 3/7] vfs: don't let the dirty time inodes get more than a day stale

Theodore Ts'o
2014-11-26T10:24:06Z

Guarantee that the on-disk timestamps will be no more than 24 hours
stale.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---
fs/fs-writeback.c | 1 +
fs/inode.c | 18 ++++++++++++++++++
include/linux/fs.h | 1 +
3 files changed, 20 insertions(+)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index ef8c5d8..529480a 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1143,6 +1143,7 @@ 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 9e464cc..37c0429 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1510,6 +1510,8 @@ 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 days_since_boot;
int ret;

if (inode->i_op->update_time) {
@@ -1526,11 +1528,26 @@ static int update_time(struct inode *inode, struct timespec *time, int flags)
if (flags & S_MTIME)
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) &&
!(inode->i_state & (I_DIRTY_SYNC | I_DIRTY_DATASYNC))) {
if (inode->i_state & I_DIRTY_TIME)
return 0;
+ get_monotonic_boottime(&uptime);
+ days_since_boot = div_u64(uptime.tv_sec, 86400);
+ if (inode->i_ts_dirty_day &&
+ (inode->i_ts_dirty_day != days_since_boot))
+ goto force_dirty;
+
spin_lock(&inode->i_lock);
if (inode->i_state & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
spin_unlock(&inode->i_lock);
@@ -1541,6 +1558,7 @@ static int update_time(struct inode *inode, struct timespec *time, int flags)
return 0;
}
inode->i_state |= I_DIRTY_TIME;
+ inode->i_ts_dirty_day = days_since_boot;
spin_unlock(&inode->i_lock);
inode_requeue_dirtytime(inode);
return 0;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 55cf34d..d0a2181 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