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Enable lazytime semantic for atime 

Linux 4.0 introduces lazytime. The idea is that when we update the atime, we
delay writing it to disk for as long as it is reasonably possible.

When lazytime is enabled, dirty_inode will be called with only I_DIRTY_TIME
flag whenever i_atime is updated. So under such condition, we will set
z_atime_dirty. We will only write it to disk if file is closed, inode is
evicted or setattr is called. Ideally, we should also write it whenever SA
is going to be updated, but it is left for future improvement.

There's one thing that we should take care of now that we allow i_atime to be
dirty. In original implementation, whenever SA is modified, zfs_inode_update
will be called to overwrite every thing in inode. This will cause dirty
i_atime to be discarded. We fix this by don't overwrite i_atime in
zfs_inode_update. We only overwrite i_atime when allocating new inode or doing
zfs_rezget with zfs_inode_update_new.

Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #4482
This commit is contained in:
Chunwei Chen 2016-03-31 16:52:03 -07:00 committed by Brian Behlendorf
parent 5137c95dec
commit 1ad7f89628
3 changed files with 110 additions and 72 deletions
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23
module/zfs/zfs_vnops.c
View File

@ -2934,8 +2934,9 @@ top:
}
if (mask & ATTR_ATIME) {
ZFS_TIME_ENCODE(&vap->va_atime, atime);
if ((mask & ATTR_ATIME) || zp->z_atime_dirty) {
zp->z_atime_dirty = 0;
ZFS_TIME_ENCODE(&ip->i_atime, atime);
SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_ATIME(zsb), NULL,
&atime, sizeof (atime));
}
@ -4048,7 +4049,7 @@ zfs_dirty_inode(struct inode *ip, int flags)
dmu_tx_t *tx;
uint64_t mode, atime[2], mtime[2], ctime[2];
sa_bulk_attr_t bulk[4];
int error;
int error = 0;
int cnt = 0;
if (zfs_is_readonly(zsb) || dmu_objset_is_snapshot(zsb->z_os))
@ -4057,6 +4058,20 @@ zfs_dirty_inode(struct inode *ip, int flags)
ZFS_ENTER(zsb);
ZFS_VERIFY_ZP(zp);
#ifdef I_DIRTY_TIME
/*
* This is the lazytime semantic indroduced in Linux 4.0
* This flag will only be called from update_time when lazytime is set.
* (Note, I_DIRTY_SYNC will also set if not lazytime)
* Fortunately mtime and ctime are managed within ZFS itself, so we
* only need to dirty atime.
*/
if (flags == I_DIRTY_TIME) {
zp->z_atime_dirty = 1;
goto out;
}
#endif
tx = dmu_tx_create(zsb->z_os);
dmu_tx_hold_sa(tx, zp->z_sa_hdl, B_FALSE);
@ -4069,6 +4084,8 @@ zfs_dirty_inode(struct inode *ip, int flags)
}
mutex_enter(&zp->z_lock);
zp->z_atime_dirty = 0;
SA_ADD_BULK_ATTR(bulk, cnt, SA_ZPL_MODE(zsb), NULL, &mode, 8);
SA_ADD_BULK_ATTR(bulk, cnt, SA_ZPL_ATIME(zsb), NULL, &atime, 16);
SA_ADD_BULK_ATTR(bulk, cnt, SA_ZPL_MTIME(zsb), NULL, &mtime, 16);

156
module/zfs/zfs_znode.c
View File

@ -482,6 +482,90 @@ zfs_inode_set_ops(zfs_sb_t *zsb, struct inode *ip)
}
}
void
zfs_set_inode_flags(znode_t *zp, struct inode *ip)
{
/*
* Linux and Solaris have different sets of file attributes, so we
* restrict this conversion to the intersection of the two.
*/
if (zp->z_pflags & ZFS_IMMUTABLE)
ip->i_flags |= S_IMMUTABLE;
else
ip->i_flags &= ~S_IMMUTABLE;
if (zp->z_pflags & ZFS_APPENDONLY)
ip->i_flags |= S_APPEND;
else
ip->i_flags &= ~S_APPEND;
}
/*
* Update the embedded inode given the znode. We should work toward
* eliminating this function as soon as possible by removing values
* which are duplicated between the znode and inode. If the generic
* inode has the correct field it should be used, and the ZFS code
* updated to access the inode. This can be done incrementally.
*/
static void
zfs_inode_update_impl(znode_t *zp, boolean_t new)
{
zfs_sb_t *zsb;
struct inode *ip;
uint32_t blksize;
u_longlong_t i_blocks;
uint64_t atime[2], mtime[2], ctime[2];
ASSERT(zp != NULL);
zsb = ZTOZSB(zp);
ip = ZTOI(zp);
/* Skip .zfs control nodes which do not exist on disk. */
if (zfsctl_is_node(ip))
return;
sa_lookup(zp->z_sa_hdl, SA_ZPL_ATIME(zsb), &atime, 16);
sa_lookup(zp->z_sa_hdl, SA_ZPL_MTIME(zsb), &mtime, 16);
sa_lookup(zp->z_sa_hdl, SA_ZPL_CTIME(zsb), &ctime, 16);
dmu_object_size_from_db(sa_get_db(zp->z_sa_hdl), &blksize, &i_blocks);
spin_lock(&ip->i_lock);
ip->i_generation = zp->z_gen;
ip->i_uid = SUID_TO_KUID(zp->z_uid);
ip->i_gid = SGID_TO_KGID(zp->z_gid);
set_nlink(ip, zp->z_links);
ip->i_mode = zp->z_mode;
zfs_set_inode_flags(zp, ip);
ip->i_blkbits = SPA_MINBLOCKSHIFT;
ip->i_blocks = i_blocks;
/*
* Only read atime from SA if we are newly created inode (or rezget),
* otherwise i_atime might be dirty.
*/
if (new)
ZFS_TIME_DECODE(&ip->i_atime, atime);
ZFS_TIME_DECODE(&ip->i_mtime, mtime);
ZFS_TIME_DECODE(&ip->i_ctime, ctime);
i_size_write(ip, zp->z_size);
spin_unlock(&ip->i_lock);
}
static void
zfs_inode_update_new(znode_t *zp)
{
zfs_inode_update_impl(zp, B_TRUE);
}
void
zfs_inode_update(znode_t *zp)
{
zfs_inode_update_impl(zp, B_FALSE);
}
/*
* Construct a znode+inode and initialize.
*
@ -549,7 +633,7 @@ zfs_znode_alloc(zfs_sb_t *zsb, dmu_buf_t *db, int blksz,
zp->z_mode = mode;
ip->i_ino = obj;
zfs_inode_update(zp);
zfs_inode_update_new(zp);
zfs_inode_set_ops(zsb, ip);
/*
@ -576,73 +660,6 @@ error:
return (NULL);
}
void
zfs_set_inode_flags(znode_t *zp, struct inode *ip)
{
/*
* Linux and Solaris have different sets of file attributes, so we
* restrict this conversion to the intersection of the two.
*/
if (zp->z_pflags & ZFS_IMMUTABLE)
ip->i_flags |= S_IMMUTABLE;
else
ip->i_flags &= ~S_IMMUTABLE;
if (zp->z_pflags & ZFS_APPENDONLY)
ip->i_flags |= S_APPEND;
else
ip->i_flags &= ~S_APPEND;
}
/*
* Update the embedded inode given the znode. We should work toward
* eliminating this function as soon as possible by removing values
* which are duplicated between the znode and inode. If the generic
* inode has the correct field it should be used, and the ZFS code
* updated to access the inode. This can be done incrementally.
*/
void
zfs_inode_update(znode_t *zp)
{
zfs_sb_t *zsb;
struct inode *ip;
uint32_t blksize;
u_longlong_t i_blocks;
uint64_t atime[2], mtime[2], ctime[2];
ASSERT(zp != NULL);
zsb = ZTOZSB(zp);
ip = ZTOI(zp);
/* Skip .zfs control nodes which do not exist on disk. */
if (zfsctl_is_node(ip))
return;
sa_lookup(zp->z_sa_hdl, SA_ZPL_ATIME(zsb), &atime, 16);
sa_lookup(zp->z_sa_hdl, SA_ZPL_MTIME(zsb), &mtime, 16);
sa_lookup(zp->z_sa_hdl, SA_ZPL_CTIME(zsb), &ctime, 16);
dmu_object_size_from_db(sa_get_db(zp->z_sa_hdl), &blksize, &i_blocks);
spin_lock(&ip->i_lock);
ip->i_generation = zp->z_gen;
ip->i_uid = SUID_TO_KUID(zp->z_uid);
ip->i_gid = SGID_TO_KGID(zp->z_gid);
set_nlink(ip, zp->z_links);
ip->i_mode = zp->z_mode;
zfs_set_inode_flags(zp, ip);
ip->i_blkbits = SPA_MINBLOCKSHIFT;
ip->i_blocks = i_blocks;
ZFS_TIME_DECODE(&ip->i_atime, atime);
ZFS_TIME_DECODE(&ip->i_mtime, mtime);
ZFS_TIME_DECODE(&ip->i_ctime, ctime);
i_size_write(ip, zp->z_size);
spin_unlock(&ip->i_lock);
}
/*
* Safely mark an inode dirty. Inodes which are part of a read-only
* file system or snapshot may not be dirtied.
@ -1206,7 +1223,8 @@ zfs_rezget(znode_t *zp)
zp->z_unlinked = (zp->z_links == 0);
zp->z_blksz = doi.doi_data_block_size;
zfs_inode_update(zp);
zp->z_atime_dirty = 0;
zfs_inode_update_new(zp);
zfs_znode_hold_exit(zsb, zh);

3
module/zfs/zpl_inode.c
View File

@ -339,6 +339,9 @@ zpl_setattr(struct dentry *dentry, struct iattr *ia)
vap->va_mtime = ia->ia_mtime;
vap->va_ctime = ia->ia_ctime;
if (vap->va_mask & ATTR_ATIME)
ip->i_atime = ia->ia_atime;
cookie = spl_fstrans_mark();
error = -zfs_setattr(ip, vap, 0, cr);
if (!error && (ia->ia_valid & ATTR_MODE))