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Implement relatime.
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Add the "relatime" property.  When set to "on", a file's atime will only
be updated if the existing atime at least a day old or if the existing
ctime or mtime has been updated since the last access.  This behavior
is compatible with the Linux "relatime" mount option.

Signed-off-by: Tim Chase <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #2064
Closes #1917
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@dweeezil @behlendorf
dweeezil authored and behlendorf committed Jan 29, 2014
1 parent 2278381 commit 6d11113
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Showing 7 changed files with 110 additions and 10 deletions.
1 change: 1 addition & 0 deletions include/sys/fs/zfs.h
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Original file line number Diff line number Diff line change
Expand Up @@ -147,6 +147,7 @@ typedef enum {
ZFS_PROP_SELINUX_FSCONTEXT,
ZFS_PROP_SELINUX_DEFCONTEXT,
ZFS_PROP_SELINUX_ROOTCONTEXT,
ZFS_PROP_RELATIME,
ZFS_NUM_PROPS
} zfs_prop_t;

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1 change: 1 addition & 0 deletions include/sys/zfs_vfsops.h
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Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,7 @@ typedef struct zfs_sb {
boolean_t z_utf8; /* utf8-only */
int z_norm; /* normalization flags */
boolean_t z_atime; /* enable atimes mount option */
boolean_t z_relatime; /* enable relatime mount option */
boolean_t z_unmounted; /* unmounted */
rrwlock_t z_teardown_lock;
krwlock_t z_teardown_inactive_lock;
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7 changes: 7 additions & 0 deletions lib/libzfs/libzfs_dataset.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1421,6 +1421,7 @@ zfs_is_namespace_prop(zfs_prop_t prop)
switch (prop) {

case ZFS_PROP_ATIME:
case ZFS_PROP_RELATIME:
case ZFS_PROP_DEVICES:
case ZFS_PROP_EXEC:
case ZFS_PROP_SETUID:
Expand Down Expand Up @@ -1756,6 +1757,11 @@ get_numeric_property(zfs_handle_t *zhp, zfs_prop_t prop, zprop_source_t *src,
mntopt_off = MNTOPT_NOATIME;
break;

case ZFS_PROP_RELATIME:
mntopt_on = MNTOPT_RELATIME;
mntopt_off = MNTOPT_NORELATIME;
break;

case ZFS_PROP_DEVICES:
mntopt_on = MNTOPT_DEVICES;
mntopt_off = MNTOPT_NODEVICES;
Expand Down Expand Up @@ -1816,6 +1822,7 @@ get_numeric_property(zfs_handle_t *zhp, zfs_prop_t prop, zprop_source_t *src,

switch (prop) {
case ZFS_PROP_ATIME:
case ZFS_PROP_RELATIME:
case ZFS_PROP_DEVICES:
case ZFS_PROP_EXEC:
case ZFS_PROP_READONLY:
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14 changes: 13 additions & 1 deletion man/man8/zfs.8
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Original file line number Diff line number Diff line change
Expand Up @@ -738,7 +738,7 @@ the \fBxattr=sa\fR property. See the \fBxattr\fR property for more details.
.ad
.sp .6
.RS 4n
Controls whether the access time for files is updated when they are read. Turning this property off avoids producing write traffic when reading files and can result in significant performance gains, though it might confuse mailers and other similar utilities. The default value is \fBon\fR.
Controls whether the access time for files is updated when they are read. Turning this property off avoids producing write traffic when reading files and can result in significant performance gains, though it might confuse mailers and other similar utilities. The default value is \fBon\fR. See also \fBrelatime\fR below.
.RE

.sp
Expand Down Expand Up @@ -1021,6 +1021,17 @@ If \fBrefreservation\fR is set, a snapshot is only allowed if there is enough fr
This property can also be referred to by its shortened column name, \fBrefreserv\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBrelatime\fR=\fBon\fR | \fBoff\fR\fR
.ad
.sp .6
.RS 4n
Controls the manner in which the access time is updated when \fBatime=on\fR is set. Turning this property \fBon\fR causes the access time to be updated relative to the modify or change time. Access time is only updated if the previous access time was earlier than the current modify or change time or if the existing access time hasn't been updated within the past 24 hours. The default value is \fBoff\fR.
.RE

.sp
.ne 2
.mk
Expand Down Expand Up @@ -3184,6 +3195,7 @@ pool/home/bob usedbyrefreservation 0 -
pool/home/bob logbias latency default
pool/home/bob dedup off default
pool/home/bob mlslabel none default
pool/home/bob relatime off default
.fi
.in -2
.sp
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2 changes: 2 additions & 0 deletions module/zcommon/zfs_prop.c
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Original file line number Diff line number Diff line change
Expand Up @@ -263,6 +263,8 @@ zfs_prop_init(void)
/* inherit index (boolean) properties */
zprop_register_index(ZFS_PROP_ATIME, "atime", 1, PROP_INHERIT,
ZFS_TYPE_FILESYSTEM, "on | off", "ATIME", boolean_table);
zprop_register_index(ZFS_PROP_RELATIME, "relatime", 0, PROP_INHERIT,
ZFS_TYPE_FILESYSTEM, "on | off", "RELATIME", boolean_table);
zprop_register_index(ZFS_PROP_DEVICES, "devices", 1, PROP_INHERIT,
ZFS_TYPE_FILESYSTEM | ZFS_TYPE_SNAPSHOT, "on | off", "DEVICES",
boolean_table);
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13 changes: 13 additions & 0 deletions module/zfs/zfs_vfsops.c
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Original file line number Diff line number Diff line change
Expand Up @@ -137,6 +137,12 @@ atime_changed_cb(void *arg, uint64_t newval)
((zfs_sb_t *)arg)->z_atime = newval;
}

static void
relatime_changed_cb(void *arg, uint64_t newval)
{
((zfs_sb_t *)arg)->z_relatime = newval;
}

static void
xattr_changed_cb(void *arg, uint64_t newval)
{
Expand Down Expand Up @@ -275,6 +281,8 @@ zfs_register_callbacks(zfs_sb_t *zsb)
dsl_pool_config_enter(dmu_objset_pool(os), FTAG);
error = dsl_prop_register(ds,
zfs_prop_to_name(ZFS_PROP_ATIME), atime_changed_cb, zsb);
error = dsl_prop_register(ds,

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@lundman

lundman Feb 11, 2014

Contributor

Should this not keep the value of "error" like the other lines do?

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@dweeezil

dweeezil Feb 11, 2014

Author Contributor

Yes, indeed. Nice catch. I'll post a pull request for this shortly.

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@behlendorf

behlendorf Feb 11, 2014

Contributor

Indeed, @lundman thanks for the extra set of eyes on this change.
zfs_prop_to_name(ZFS_PROP_RELATIME), relatime_changed_cb, zsb);
error = error ? error : dsl_prop_register(ds,
zfs_prop_to_name(ZFS_PROP_XATTR), xattr_changed_cb, zsb);
error = error ? error : dsl_prop_register(ds,
Expand Down Expand Up @@ -314,6 +322,8 @@ zfs_register_callbacks(zfs_sb_t *zsb)
*/
(void) dsl_prop_unregister(ds, zfs_prop_to_name(ZFS_PROP_ATIME),
atime_changed_cb, zsb);
(void) dsl_prop_unregister(ds, zfs_prop_to_name(ZFS_PROP_RELATIME),
relatime_changed_cb, zsb);
(void) dsl_prop_unregister(ds, zfs_prop_to_name(ZFS_PROP_XATTR),
xattr_changed_cb, zsb);
(void) dsl_prop_unregister(ds, zfs_prop_to_name(ZFS_PROP_RECORDSIZE),
Expand Down Expand Up @@ -914,6 +924,9 @@ zfs_unregister_callbacks(zfs_sb_t *zsb)
VERIFY(dsl_prop_unregister(ds, "atime", atime_changed_cb,
zsb) == 0);

VERIFY(dsl_prop_unregister(ds, "relatime", relatime_changed_cb,
zsb) == 0);

VERIFY(dsl_prop_unregister(ds, "xattr", xattr_changed_cb,
zsb) == 0);

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82 changes: 73 additions & 9 deletions module/zfs/zfs_znode.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1109,25 +1109,89 @@ zfs_zinactive(znode_t *zp)
ZFS_OBJ_HOLD_EXIT(zsb, z_id);
}

static inline int
zfs_compare_timespec(struct timespec *t1, struct timespec *t2)
{
if (t1->tv_sec < t2->tv_sec)
return (-1);

if (t1->tv_sec > t2->tv_sec)
return (1);

return (t1->tv_nsec - t2->tv_nsec);
}

/*
* Determine whether the znode's atime must be updated. The logic mostly
* duplicates the Linux kernel's relatime_need_update() functionality.
* This function is only called if the underlying filesystem actually has
* atime updates enabled.
*/
static inline boolean_t
zfs_atime_need_update(znode_t *zp, timestruc_t *now)
{
if (!ZTOZSB(zp)->z_relatime)
return (B_TRUE);

/*
* In relatime mode, only update the atime if the previous atime
* is earlier than either the ctime or mtime or if at least a day
* has passed since the last update of atime.
*/
if (zfs_compare_timespec(&ZTOI(zp)->i_mtime, &ZTOI(zp)->i_atime) >= 0)
return (B_TRUE);

if (zfs_compare_timespec(&ZTOI(zp)->i_ctime, &ZTOI(zp)->i_atime) >= 0)
return (B_TRUE);

if ((long)now->tv_sec - ZTOI(zp)->i_atime.tv_sec >= 24*60*60)
return (B_TRUE);

return (B_FALSE);
}

/*
* Prepare to update znode time stamps.
*
* IN: zp - znode requiring timestamp update
* flag - ATTR_MTIME, ATTR_CTIME, ATTR_ATIME flags
* have_tx - true of caller is creating a new txg
*
* OUT: zp - new atime (via underlying inode's i_atime)
* mtime - new mtime
* ctime - new ctime
*
* NOTE: The arguments are somewhat redundant. The following condition
* is always true:
*
* have_tx == !(flag & ATTR_ATIME)
*/
void
zfs_tstamp_update_setup(znode_t *zp, uint_t flag, uint64_t mtime[2],
uint64_t ctime[2], boolean_t have_tx)
{
timestruc_t now;

ASSERT(have_tx == !(flag & ATTR_ATIME));
gethrestime(&now);

if (have_tx) { /* will sa_bulk_update happen really soon? */
/*
* NOTE: The following test intentionally does not update z_atime_dirty
* in the case where an ATIME update has been requested but for which
* the update is omitted due to relatime logic. The rationale being
* that if the flag was set somewhere else, we should leave it alone
* here.
*/
if (flag & ATTR_ATIME) {
if (zfs_atime_need_update(zp, &now)) {
ZFS_TIME_ENCODE(&now, zp->z_atime);
ZTOI(zp)->i_atime.tv_sec = zp->z_atime[0];
ZTOI(zp)->i_atime.tv_nsec = zp->z_atime[1];
zp->z_atime_dirty = 1;
}
} else {
zp->z_atime_dirty = 0;
zp->z_seq++;
} else {
zp->z_atime_dirty = 1;
}

if (flag & ATTR_ATIME) {
ZFS_TIME_ENCODE(&now, zp->z_atime);
ZTOI(zp)->i_atime.tv_sec = zp->z_atime[0];
ZTOI(zp)->i_atime.tv_nsec = zp->z_atime[1];
}

if (flag & ATTR_MTIME) {
Expand Down

2 comments on commit 6d11113

@CMCDragonkai
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@behlendorf So can one set atime=off and relatime=on. Does both need to be on to take effect?

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@CMCDragonkai relatime=[on|off] will have no effect unless atime=on

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