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Reintroduce zfs_remove() synchronous deletes

Browse Source 
Reintroduce a slightly adapted version of the Illumos logic for
synchronous unlinks.  The basic idea here is that only files
smaller than zfs_delete_blocks (20480) blocks should be deleted
synchronously.  Unlinking larger files should be handled
asynchronously to minimize impact to the caller.

To accomplish this iput() which is responsible for calling
zfs_znode_delete() on Linux is only called in the delete_now
path.  Otherwise zfs_async_iput() is used which allows the
last reference to be dropped by a taskq thread effectively
making the removal asynchronous.

Porting notes:
- Add zfs_delete_blocks module option for performance analysis.
  The default value is DMU_MAX_DELETEBLKCNT which is the same
  as upstream.  Reducing this value means that smaller files
  will be unlinked asynchronously like large files.
- All occurrences of zfsvfs changes to zsb.

Ported-by: KernelOfTruth kerneloftruth@gmail.com
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This commit is contained in:
kernelOfTruth 2015-08-21 03:43:10 +02:00 committed by Brian Behlendorf
parent 460a021391
commit a966c5640e
2 changed files with 81 additions and 12 deletions
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15
man/man5/zfs-module-parameters.5
View File

@ -715,6 +715,21 @@ Note: \fBzfs_delay_scale\fR * \fBzfs_dirty_data_max\fR must be < 2^64.
Default value: \fB500,000\fR.
.RE
.sp
.ne 2
.na
\fBzfs_delete_blocks\fR (ulong)
.ad
.RS 12n
This is the used to define a large file for the purposes of delete. Files
containing more than \fBzfs_delete_blocks\fR will be deleted asynchronously
while smaller files are deleted synchronously. Decreasing this value will
reduce the time spent in an unlink(2) system call at the expense of a longer
delay before the freed space is available.
.sp
Default value: \fB20,480\fR.
.RE
.sp
.ne 2
.na

78
module/zfs/zfs_vnops.c
View File

@ -418,6 +418,7 @@ mappedread(struct inode *ip, int nbytes, uio_t *uio)
#endif /* _KERNEL */
unsigned long zfs_read_chunk_size = 1024 * 1024; /* Tunable */
unsigned long zfs_delete_blocks = DMU_MAX_DELETEBLKCNT;
/*
* Read bytes from specified file into supplied buffer.
@ -1520,13 +1521,13 @@ zfs_remove(struct inode *dip, char *name, cred_t *cr)
struct inode *ip;
zfs_sb_t *zsb = ITOZSB(dip);
zilog_t *zilog;
uint64_t xattr_obj;
uint64_t acl_obj, xattr_obj;
uint64_t xattr_obj_unlinked = 0;
uint64_t obj = 0;
zfs_dirlock_t *dl;
dmu_tx_t *tx;
boolean_t may_delete_now;
boolean_t unlinked;
boolean_t may_delete_now, delete_now = FALSE;
boolean_t unlinked, toobig = FALSE;
uint64_t txtype;
pathname_t *realnmp = NULL;
#ifdef HAVE_PN_UTILS
@ -1590,9 +1591,10 @@ top:
mutex_exit(&zp->z_lock);
/*
* We never delete the znode and always place it in the unlinked
* set. The dentry cache will always hold the last reference and
* is responsible for safely freeing the znode.
* We may delete the znode now, or we may put it in the unlinked set;
* it depends on whether we're the last link, and on whether there are
* other holds on the inode. So we dmu_tx_hold() the right things to
* allow for either case.
*/
obj = zp->z_id;
tx = dmu_tx_create(zsb->z_os);
@ -1600,6 +1602,12 @@ top:
dmu_tx_hold_sa(tx, zp->z_sa_hdl, B_FALSE);
zfs_sa_upgrade_txholds(tx, zp);
zfs_sa_upgrade_txholds(tx, dzp);
if (may_delete_now) {
toobig = zp->z_size > zp->z_blksz * zfs_delete_blocks;
/* if the file is too big, only hold_free a token amount */
dmu_tx_hold_free(tx, zp->z_id, 0,
(toobig ? DMU_MAX_ACCESS : DMU_OBJECT_END));
}
/* are there any extended attributes? */
error = sa_lookup(zp->z_sa_hdl, SA_ZPL_XATTR(zsb),
@ -1611,6 +1619,11 @@ top:
dmu_tx_hold_sa(tx, xzp->z_sa_hdl, B_FALSE);
}
mutex_enter(&zp->z_lock);
if ((acl_obj = zfs_external_acl(zp)) != 0 && may_delete_now)
dmu_tx_hold_free(tx, acl_obj, 0, DMU_OBJECT_END);
mutex_exit(&zp->z_lock);
/* charge as an update -- would be nice not to charge at all */
dmu_tx_hold_zap(tx, zsb->z_unlinkedobj, FALSE, NULL);
@ -1662,6 +1675,42 @@ top:
mutex_enter(&zp->z_lock);
(void) sa_lookup(zp->z_sa_hdl, SA_ZPL_XATTR(zsb),
&xattr_obj_unlinked, sizeof (xattr_obj_unlinked));
delete_now = may_delete_now && !toobig &&
atomic_read(&ip->i_count) == 1 && !(zp->z_is_mapped) &&
xattr_obj == xattr_obj_unlinked && zfs_external_acl(zp) ==
acl_obj;
}
if (delete_now) {
if (xattr_obj_unlinked) {
ASSERT3U(xzp->z_links, ==, 2);
mutex_enter(&xzp->z_lock);
xzp->z_unlinked = 1;
xzp->z_links = 0;
error = sa_update(xzp->z_sa_hdl, SA_ZPL_LINKS(zsb),
&xzp->z_links, sizeof (xzp->z_links), tx);
ASSERT3U(error, ==, 0);
mutex_exit(&xzp->z_lock);
zfs_unlinked_add(xzp, tx);
if (zp->z_is_sa)
error = sa_remove(zp->z_sa_hdl,
SA_ZPL_XATTR(zsb), tx);
else
error = sa_update(zp->z_sa_hdl,
SA_ZPL_XATTR(zsb), &null_xattr,
sizeof (uint64_t), tx);
ASSERT0(error);
}
/*
* Add to the unlinked set because a new reference could be
* taken concurrently resulting in a deferred destruction.
*/
zfs_unlinked_add(zp, tx);
mutex_exit(&zp->z_lock);
zfs_inode_update(zp);
iput(ip);
} else if (unlinked) {
mutex_exit(&zp->z_lock);
zfs_unlinked_add(zp, tx);
}
@ -1682,13 +1731,16 @@ out:
zfs_dirent_unlock(dl);
zfs_inode_update(dzp);
zfs_inode_update(zp);
if (xzp)
zfs_inode_update(xzp);
iput(ip);
if (xzp)
iput(ZTOI(xzp));
if (!delete_now) {
zfs_inode_update(zp);
zfs_iput_async(ip);
}
if (xzp) {
zfs_inode_update(xzp);
zfs_iput_async(ZTOI(xzp));
}
if (zsb->z_os->os_sync == ZFS_SYNC_ALWAYS)
zil_commit(zilog, 0);
@ -4710,6 +4762,8 @@ zfs_retzcbuf(struct inode *ip, xuio_t *xuio, cred_t *cr)
#endif /* HAVE_UIO_ZEROCOPY */
#if defined(_KERNEL) && defined(HAVE_SPL)
module_param(zfs_delete_blocks, ulong, 0644);
MODULE_PARM_DESC(zfs_delete_blocks, "Delete files larger than N blocks async");
module_param(zfs_read_chunk_size, long, 0644);
MODULE_PARM_DESC(zfs_read_chunk_size, "Bytes to read per chunk");
#endif