mirror_zfs/include/sys
Chunwei Chen 0df9673f01 Fix atime handling and relatime
The problem for atime:

We have 3 places for atime: inode->i_atime, znode->z_atime and SA. And its
handling is a mess. A huge part of mess regarding atime comes from
zfs_tstamp_update_setup, zfs_inode_update, and zfs_getattr, which behave
inconsistently with those three values.

zfs_tstamp_update_setup clears z_atime_dirty unconditionally as long as you
don't pass ATTR_ATIME. Which means every write(2) operation which only updates
ctime and mtime will cause atime changes to not be written to disk.

Also zfs_inode_update from write(2) will replace inode->i_atime with what's
inside SA(stale). But doesn't touch z_atime. So after read(2) and write(2).
You'll have i_atime(stale), z_atime(new), SA(stale) and z_atime_dirty=0.

Now, if you do stat(2), zfs_getattr will actually replace i_atime with what's
inside, z_atime. So you will have now you'll have i_atime(new), z_atime(new),
SA(stale) and z_atime_dirty=0. These will all gone after umount. And you'll
leave with a stale atime.

The problem for relatime:

We do have a relatime config inside ZFS dataset, but how it should interact
with the mount flag MS_RELATIME is not well defined. It seems it wanted
relatime mount option to override the dataset config by showing it as
temporary in `zfs get`. But at the same time, `zfs set relatime=on|off` would
also seems to want to override the mount option. Not to mention that
MS_RELATIME flag is actually never passed into ZFS, so it never really worked.

How Linux handles atime:

The Linux kernel actually handles atime completely in VFS, except for writing
it to disk. So if we remove the atime handling in ZFS, things would just work,
no matter it's strictatime, relatime, noatime, or even O_NOATIME. And whenever
VFS updates the i_atime, it will notify the underlying filesystem via
sb->dirty_inode().

And also there's one thing to note about atime flags like MS_RELATIME and
other flags like MS_NODEV, etc. They are mount point flags rather than
filesystem(sb) flags. Since native linux filesystem can be mounted at multiple
places at the same time, they can all have different atime settings. So these
flags are never passed down to filesystem drivers.

What this patch tries to do:

We remove znode->z_atime, since we won't gain anything from it. We remove most
of the atime handling and leave it to VFS. The only thing we do with atime is
to write it when dirty_inode() or setattr() is called. We also add
file_accessed() in zpl_read() since it's not provided in vfs_read().

After this patch, only the MS_RELATIME flag will have effect. The setting in
dataset won't do anything. We will make zfstuil to mount ZFS with MS_RELATIME
set according to the setting in dataset in future patch.

Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #4482
2016-04-05 18:54:55 -07:00
..
fm Illumos 3749 - zfs event processing should work on R/O root filesystems 2016-01-12 14:42:32 -08:00
fs Illumos 4929 - want prevsnap property 2016-01-11 11:58:26 -08:00
arc_impl.h Illumos 6214 - zpools going south 2015-09-11 11:14:38 -07:00
arc.h Illumos 5987 - zfs prefetch code needs work 2016-01-12 09:02:33 -08:00
avl_impl.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
avl.h Illumos 4745 - fix AVL code misspellings 2015-07-10 11:58:37 -07:00
blkptr.h Illumos 4757, 4913 2014-08-01 14:28:05 -07:00
bplist.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
bpobj.h Illumos 5810 - zdb should print details of bpobj 2015-05-11 15:10:24 -07:00
bptree.h Illumos 4914 - zfs on-disk bookmark structure should be named *_phys_t 2014-08-06 14:48:41 -07:00
bqueue.h Illumos 5960, 5925 2016-01-08 15:08:19 -08:00
dbuf.h Illumos 5960, 5925 2016-01-08 15:08:19 -08:00
ddt.h Add ddt, ddt_entry, and l2arc_hdr caches 2014-01-07 10:33:11 -08:00
dmu_impl.h Illumos 4757, 4913 2014-08-01 14:28:05 -07:00
dmu_objset.h Illumos 6267 - dn_bonus evicted too early 2015-10-13 14:12:02 -07:00
dmu_send.h Illumos 5765 - add support for estimating send stream size with lzc_send_space when source is a bookmark 2015-05-13 09:03:59 -07:00
dmu_traverse.h Illumos 4914 - zfs on-disk bookmark structure should be named *_phys_t 2014-08-06 14:48:41 -07:00
dmu_tx.h dmu_tx kstat cleanup 2014-03-04 12:22:24 -08:00
dmu_zfetch.h Illumos 5987 - zfs prefetch code needs work 2016-01-12 09:02:33 -08:00
dmu.h Illumos 4950 - files sometimes can't be removed from a full filesystem 2016-01-21 16:59:30 -08:00
dnode.h Illumos 5141 - zfs minimum indirect block size is 4K 2016-01-12 14:11:31 -08:00
dsl_bookmark.h Illumos 4368, 4369. 2014-07-29 10:55:29 -07:00
dsl_dataset.h Illumos 6171 - dsl_prop_unregister() slows down dataset eviction. 2016-01-12 10:53:12 -08:00
dsl_deadlist.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
dsl_deleg.h Illumos 4368, 4369. 2014-07-29 10:55:29 -07:00
dsl_destroy.h Illumos #3888 2013-11-04 11:18:14 -08:00
dsl_dir.h Illumos 6171 - dsl_prop_unregister() slows down dataset eviction. 2016-01-12 10:53:12 -08:00
dsl_pool.h Illumos 5981 - Deadlock in dmu_objset_find_dp 2015-07-06 09:31:35 -07:00
dsl_prop.h Illumos 6171 - dsl_prop_unregister() slows down dataset eviction. 2016-01-12 10:53:12 -08:00
dsl_scan.h Illumos 4914 - zfs on-disk bookmark structure should be named *_phys_t 2014-08-06 14:48:41 -07:00
dsl_synctask.h Illumos 4951 - ZFS administrative commands should use reserved space 2015-05-04 09:41:10 -07:00
dsl_userhold.h Illumos #3740 2013-11-04 11:17:48 -08:00
efi_partition.h Ext4's typical GPT partition type not recognized 2015-12-04 09:27:00 -08:00
Makefile.am Illumos 5960, 5925 2016-01-08 15:08:19 -08:00
metaslab_impl.h Remove fastwrite mutex 2016-01-15 15:38:35 -08:00
metaslab.h Illumos 5213 - panic in metaslab_init due to space_map_open returning ENXIO 2014-11-14 15:37:45 -08:00
mntent.h Honor xattr=sa dataset property 2015-09-19 14:04:14 -07:00
multilist.h Illumos 5497 - lock contention on arcs_mtx 2015-06-11 10:27:25 -07:00
nvpair_impl.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
nvpair.h Replace __va_list with va_list 2014-08-13 10:35:00 -07:00
range_tree.h Illumos #4374 2014-07-30 09:20:35 -07:00
refcount.h Illumos 5045 - use atomic_{inc,dec}_* instead of atomic_add_* 2016-01-15 15:38:36 -08:00
rrwlock.h Illumos 5008 - lock contention (rrw_exit) while running a read only load 2015-07-06 09:34:13 -07:00
sa_impl.h Illumos 5056 - ZFS deadlock on db_mtx and dn_holds 2015-04-28 16:25:34 -07:00
sa.h Prevent SA length overflow 2015-12-30 13:20:12 -08:00
sdt.h Swap DTRACE_PROBE* with Linux tracepoints 2014-11-17 11:13:55 -08:00
spa_boot.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
spa_impl.h Add support for asynchronous zvol minor operations 2016-03-10 09:49:22 -08:00
spa.h Illumos 5746 - more checksumming in zfs send 2015-12-30 14:24:14 -08:00
space_map.h Illumos 5164-5165 - space map fixes 2014-10-23 15:30:32 -07:00
space_reftree.h Illumos #4101, #4102, #4103, #4105, #4106 2014-07-22 09:39:16 -07:00
trace_acl.h Fix atime handling and relatime 2016-04-05 18:54:55 -07:00
trace_arc.h Illumos 5987 - zfs prefetch code needs work 2016-01-12 09:02:33 -08:00
trace_dbgmsg.h SET_ERROR should print strings 2016-01-15 15:38:35 -08:00
trace_dbuf.h SET_ERROR should print strings 2016-01-15 15:38:35 -08:00
trace_dmu.h Fix build failure with Linux 4.1 and FTRACE 2015-07-29 07:35:06 -07:00
trace_dnode.h Fix build failure with Linux 4.1 and FTRACE 2015-07-29 07:35:06 -07:00
trace_multilist.h Fix build failure with Linux 4.1 and FTRACE 2015-08-18 16:47:21 -07:00
trace_txg.h Fix build failure with Linux 4.1 and FTRACE 2015-07-29 07:35:06 -07:00
trace_zil.h Fix build failure with Linux 4.1 and FTRACE 2015-07-29 07:35:06 -07:00
trace_zrlock.h SET_ERROR should print strings 2016-01-15 15:38:35 -08:00
trace.h Remove duplicate typedefs from trace.h 2015-01-06 16:53:24 -08:00
txg_impl.h Illumos #4045 write throttle & i/o scheduler performance work 2013-12-06 09:32:43 -08:00
txg.h Illumos 4753 - increase number of outstanding async writes when sync task is waiting 2014-09-23 13:50:55 -07:00
u8_textprep_data.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
u8_textprep.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
uberblock_impl.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
uberblock.h Illumos 5347 - idle pool may run itself out of space 2015-07-14 10:35:21 -07:00
uio_impl.h Add basic uio support 2011-02-10 09:21:43 -08:00
unique.h Illumos #3742 2013-11-04 10:55:25 -08:00
uuid.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
vdev_disk.h cstyle: Resolve C style issues 2013-12-18 16:46:35 -08:00
vdev_file.h Update all default taskq settings 2015-06-25 08:58:16 -07:00
vdev_impl.h FreeBSD r256956: Improve ZFS N-way mirror read performance by using load and locality information. 2016-02-26 11:24:35 -08:00
vdev.h FreeBSD r256956: Improve ZFS N-way mirror read performance by using load and locality information. 2016-02-26 11:24:35 -08:00
xvattr.h Add xvattr support 2011-03-02 11:43:50 -08:00
zap_impl.h Illumos 5027 - zfs large block support 2015-05-11 12:23:16 -07:00
zap_leaf.h Illumos 5056 - ZFS deadlock on db_mtx and dn_holds 2015-04-28 16:25:34 -07:00
zap.h Add zap_prefetch() interface 2015-12-04 09:39:20 -08:00
zfeature.h Illumos 4370, 4371 2014-07-28 14:29:58 -07:00
zfs_acl.h Illumos #3742 2013-11-04 10:55:25 -08:00
zfs_context.h Ensure correct return value type 2016-03-29 18:33:17 -07:00
zfs_ctldir.h Use spa as key besides objsetid for snapentry 2015-12-08 16:38:56 -08:00
zfs_debug.h Add dbgmsg kstat 2015-09-04 16:08:14 -07:00
zfs_delay.h cstyle: Resolve C style issues 2013-12-18 16:46:35 -08:00
zfs_dir.h Prototype/structure update for Linux 2011-02-10 09:27:21 -08:00
zfs_fuid.h Prototype/structure update for Linux 2011-02-10 09:27:21 -08:00
zfs_ioctl.h Illumos 5746 - more checksumming in zfs send 2015-12-30 14:24:14 -08:00
zfs_onexit.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
zfs_rlock.h Illumos #3742 2013-11-04 10:55:25 -08:00
zfs_sa.h Illumos 5027 - zfs large block support 2015-05-11 12:23:16 -07:00
zfs_stat.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
zfs_vfsops.h Fix zsb->z_hold_mtx deadlock 2016-01-15 15:33:45 -08:00
zfs_vnops.h Add zfs_iput_async() interface 2014-08-11 16:11:43 -07:00
zfs_znode.h Fix atime handling and relatime 2016-04-05 18:54:55 -07:00
zil_impl.h Illumos 5027 - zfs large block support 2015-05-11 12:23:16 -07:00
zil.h Illumos 5269 - zpool import slow 2015-06-09 13:48:02 -07:00
zio_checksum.h Illumos 5960, 5925 2016-01-08 15:08:19 -08:00
zio_compress.h Illumos #3742 2013-11-04 10:55:25 -08:00
zio_impl.h Illumos #3836 2013-11-05 12:14:56 -08:00
zio_priority.h Illumos 5960, 5925 2016-01-08 15:08:19 -08:00
zio.h Illumos 5960, 5925 2016-01-08 15:08:19 -08:00
zpl.h Add temporary mount options 2015-09-03 14:14:55 -07:00
zrlock.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
zvol.h Add support for asynchronous zvol minor operations 2016-03-10 09:49:22 -08:00