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After some ZIL changes 6 years ago zil_slog_limit got partially broken

Browse Source 
due to zl_itx_list_sz not updated when async itx'es upgraded to sync.
Actually because of other changes about that time zl_itx_list_sz is not
really required to implement the functionality, so this patch removes
some unneeded broken code and variables.

Original idea of zil_slog_limit was to reduce chance of SLOG abuse by
single heavy logger, that increased latency for other (more latency critical)
loggers, by pushing heavy log out into the main pool instead of SLOG. Beside
huge latency increase for heavy writers, this implementation caused double
write of all data, since the log records were explicitly prepared for SLOG.
Since we now have I/O scheduler, I've found it can be much more efficient
to reduce priority of heavy logger SLOG writes from ZIO_PRIORITY_SYNC_WRITE
to ZIO_PRIORITY_ASYNC_WRITE, while still leave them on SLOG.

Existing ZIL implementation had problem with space efficiency when it
has to write large chunks of data into log blocks of limited size. In some
cases efficiency stopped to almost as low as 50%. In case of ZIL stored on
spinning rust, that also reduced log write speed in half, since head had to
uselessly fly over allocated but not written areas. This change improves
the situation by offloading problematic operations from z*_log_write() to
zil_lwb_commit(), which knows real situation of log blocks allocation and
can split large requests into pieces much more efficiently. Also as side
effect it removes one of two data copy operations done by ZIL code WR_COPIED
case.

While there, untangle and unify code of z*_log_write() functions.
Also zfs_log_write() alike to zvol_log_write() can now handle writes crossing
block boundary, that may also improve efficiency if ZPL is made to do that.

Sponsored by:	iXsystems, Inc.
This commit is contained in:
Alexander Motin 2016-11-17 21:01:27 +00:00
parent eb9bfc257d
commit 14b5719f6a
8 changed files with 100 additions and 110 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
cddl/contrib/opensolaris/cmd/ztest/ztest.c
View File

@ -1371,7 +1371,6 @@ ztest_log_write(ztest_ds_t *zd, dmu_tx_t *tx, lr_write_t *lr)
itx->itx_private = zd;
itx->itx_wr_state = write_state;
itx->itx_sync = (ztest_random(8) == 0);
itx->itx_sod += (write_state == WR_NEED_COPY ? lr->lr_length : 0);
bcopy(&lr->lr_common + 1, &itx->itx_lr + 1,
sizeof (*lr) - sizeof (lr_t));

1
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/zil.h
View File

@ -369,7 +369,6 @@ typedef struct itx {
void *itx_private; /* type-specific opaque data */
itx_wr_state_t itx_wr_state; /* write state */
uint8_t itx_sync; /* synchronous transaction */
uint64_t itx_sod; /* record size on disk */
uint64_t itx_oid; /* object id */
lr_t itx_lr; /* common part of log record */
/* followed by type-specific part of lr_xx_t and its immediate data */

5
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/zil_impl.h
View File

@ -42,6 +42,7 @@ extern "C" {
typedef struct lwb {
zilog_t *lwb_zilog; /* back pointer to log struct */
blkptr_t lwb_blk; /* on disk address of this log blk */
boolean_t lwb_slog; /* lwb_blk is on SLOG device */
int lwb_nused; /* # used bytes in buffer */
int lwb_sz; /* size of block and buffer */
char *lwb_buf; /* log write buffer */
@ -62,7 +63,6 @@ typedef struct itxs {
typedef struct itxg {
kmutex_t itxg_lock; /* lock for this structure */
uint64_t itxg_txg; /* txg for this chain */
uint64_t itxg_sod; /* total size on disk for this txg */
itxs_t *itxg_itxs; /* sync and async itxs */
} itxg_t;
@ -120,7 +120,6 @@ struct zilog {
kcondvar_t zl_cv_batch[2]; /* batch condition variables */
itxg_t zl_itxg[TXG_SIZE]; /* intent log txg chains */
list_t zl_itx_commit_list; /* itx list to be committed */
uint64_t zl_itx_list_sz; /* total size of records on list */
uint64_t zl_cur_used; /* current commit log size used */
list_t zl_lwb_list; /* in-flight log write list */
kmutex_t zl_vdev_lock; /* protects zl_vdev_tree */
@ -142,6 +141,8 @@ typedef struct zil_bp_node {
#define ZIL_MAX_LOG_DATA (SPA_OLD_MAXBLOCKSIZE - sizeof (zil_chain_t) - \
sizeof (lr_write_t))
#define ZIL_MAX_COPIED_DATA \
((SPA_OLD_MAXBLOCKSIZE - sizeof (zil_chain_t)) / 2 - sizeof (lr_write_t))
#ifdef __cplusplus
}

2
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/zio.h
View File

@ -547,7 +547,7 @@ extern zio_t *zio_free_sync(zio_t *pio, spa_t *spa, uint64_t txg,
const blkptr_t *bp, uint64_t size, enum zio_flag flags);
extern int zio_alloc_zil(spa_t *spa, uint64_t txg, blkptr_t *new_bp,
blkptr_t *old_bp, uint64_t size, boolean_t use_slog);
blkptr_t *old_bp, uint64_t size, boolean_t *slog);
extern void zio_free_zil(spa_t *spa, uint64_t txg, blkptr_t *bp);
extern void zio_flush(zio_t *zio, vdev_t *vd);
extern zio_t *zio_trim(zio_t *zio, spa_t *spa, vdev_t *vd, uint64_t offset,

37
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_log.c
View File

@ -464,20 +464,17 @@ void
zfs_log_write(zilog_t *zilog, dmu_tx_t *tx, int txtype,
znode_t *zp, offset_t off, ssize_t resid, int ioflag)
{
uint32_t blocksize = zp->z_blksz;
itx_wr_state_t write_state;
boolean_t slogging;
uintptr_t fsync_cnt;
ssize_t immediate_write_sz;
if (zil_replaying(zilog, tx) || zp->z_unlinked)
return;
immediate_write_sz = (zilog->zl_logbias == ZFS_LOGBIAS_THROUGHPUT)
? 0 : zfs_immediate_write_sz;
slogging = spa_has_slogs(zilog->zl_spa) &&
(zilog->zl_logbias == ZFS_LOGBIAS_LATENCY);
if (resid > immediate_write_sz && !slogging && resid <= zp->z_blksz)
if (zilog->zl_logbias == ZFS_LOGBIAS_THROUGHPUT)
write_state = WR_INDIRECT;
else if (!spa_has_slogs(zilog->zl_spa) &&
resid >= zfs_immediate_write_sz)
write_state = WR_INDIRECT;
else if (ioflag & (FSYNC | FDSYNC))
write_state = WR_COPIED;
@ -491,30 +488,26 @@ zfs_log_write(zilog_t *zilog, dmu_tx_t *tx, int txtype,
while (resid) {
itx_t *itx;
lr_write_t *lr;
ssize_t len;
itx_wr_state_t wr_state = write_state;
ssize_t len = resid;
/*
* If the write would overflow the largest block then split it.
*/
if (write_state != WR_INDIRECT && resid > ZIL_MAX_LOG_DATA)
len = SPA_OLD_MAXBLOCKSIZE >> 1;
else
len = resid;
if (wr_state == WR_COPIED && resid > ZIL_MAX_COPIED_DATA)
wr_state = WR_NEED_COPY;
else if (wr_state == WR_INDIRECT)
len = MIN(blocksize - P2PHASE(off, blocksize), resid);
itx = zil_itx_create(txtype, sizeof (*lr) +
(write_state == WR_COPIED ? len : 0));
(wr_state == WR_COPIED ? len : 0));
lr = (lr_write_t *)&itx->itx_lr;
if (write_state == WR_COPIED && dmu_read(zp->z_zfsvfs->z_os,
if (wr_state == WR_COPIED && dmu_read(zp->z_zfsvfs->z_os,
zp->z_id, off, len, lr + 1, DMU_READ_NO_PREFETCH) != 0) {
zil_itx_destroy(itx);
itx = zil_itx_create(txtype, sizeof (*lr));
lr = (lr_write_t *)&itx->itx_lr;
write_state = WR_NEED_COPY;
wr_state = WR_NEED_COPY;
}
itx->itx_wr_state = write_state;
if (write_state == WR_NEED_COPY)
itx->itx_sod += len;
itx->itx_wr_state = wr_state;
lr->lr_foid = zp->z_id;
lr->lr_offset = off;
lr->lr_length = len;

99
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zil.c
View File

@ -88,6 +88,15 @@ SYSCTL_DECL(_vfs_zfs_trim);
SYSCTL_INT(_vfs_zfs_trim, OID_AUTO, enabled, CTLFLAG_RDTUN, &zfs_trim_enabled, 0,
"Enable ZFS TRIM");
/*
* Limit SLOG write size per commit executed with synchronous priority.
* Any writes above that executed with lower (asynchronous) priority to
* limit potential SLOG device abuse by single active ZIL writer.
*/
uint64_t zil_slog_limit = 768 * 1024;
SYSCTL_QUAD(_vfs_zfs, OID_AUTO, zil_slog_limit, CTLFLAG_RWTUN,
&zil_slog_limit, 0, "Maximal SLOG commit size with sync priority");
static kmem_cache_t *zil_lwb_cache;
#define LWB_EMPTY(lwb) ((BP_GET_LSIZE(&lwb->lwb_blk) - \
@ -447,13 +456,14 @@ zil_free_log_record(zilog_t *zilog, lr_t *lrc, void *tx, uint64_t claim_txg)
}
static lwb_t *
zil_alloc_lwb(zilog_t *zilog, blkptr_t *bp, uint64_t txg)
zil_alloc_lwb(zilog_t *zilog, blkptr_t *bp, boolean_t slog, uint64_t txg)
{
lwb_t *lwb;
lwb = kmem_cache_alloc(zil_lwb_cache, KM_SLEEP);
lwb->lwb_zilog = zilog;
lwb->lwb_blk = *bp;
lwb->lwb_slog = slog;
lwb->lwb_buf = zio_buf_alloc(BP_GET_LSIZE(bp));
lwb->lwb_max_txg = txg;
lwb->lwb_zio = NULL;
@ -516,6 +526,7 @@ zil_create(zilog_t *zilog)
dmu_tx_t *tx = NULL;
blkptr_t blk;
int error = 0;
boolean_t slog = FALSE;
/*
* Wait for any previous destroy to complete.
@ -544,7 +555,7 @@ zil_create(zilog_t *zilog)
}
error = zio_alloc_zil(zilog->zl_spa, txg, &blk, NULL,
ZIL_MIN_BLKSZ, zilog->zl_logbias == ZFS_LOGBIAS_LATENCY);
ZIL_MIN_BLKSZ, &slog);
if (error == 0)
zil_init_log_chain(zilog, &blk);
@ -554,7 +565,7 @@ zil_create(zilog_t *zilog)
* Allocate a log write buffer (lwb) for the first log block.
*/
if (error == 0)
lwb = zil_alloc_lwb(zilog, &blk, txg);
lwb = zil_alloc_lwb(zilog, &blk, slog, txg);
/*
* If we just allocated the first log block, commit our transaction
@ -885,6 +896,7 @@ static void
zil_lwb_write_init(zilog_t *zilog, lwb_t *lwb)
{
zbookmark_phys_t zb;
zio_priority_t prio;
SET_BOOKMARK(&zb, lwb->lwb_blk.blk_cksum.zc_word[ZIL_ZC_OBJSET],
ZB_ZIL_OBJECT, ZB_ZIL_LEVEL,
@ -895,9 +907,13 @@ zil_lwb_write_init(zilog_t *zilog, lwb_t *lwb)
ZIO_FLAG_CANFAIL);
}
if (lwb->lwb_zio == NULL) {
if (zilog->zl_cur_used <= zil_slog_limit || !lwb->lwb_slog)
prio = ZIO_PRIORITY_SYNC_WRITE;
else
prio = ZIO_PRIORITY_ASYNC_WRITE;
lwb->lwb_zio = zio_rewrite(zilog->zl_root_zio, zilog->zl_spa,
0, &lwb->lwb_blk, lwb->lwb_buf, BP_GET_LSIZE(&lwb->lwb_blk),
zil_lwb_write_done, lwb, ZIO_PRIORITY_SYNC_WRITE,
zil_lwb_write_done, lwb, prio,
ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_PROPAGATE, &zb);
}
}
@ -916,18 +932,6 @@ uint64_t zil_block_buckets[] = {
UINT64_MAX
};
/*
* Use the slog as long as the logbias is 'latency' and the current commit size
* is less than the limit or the total list size is less than 2X the limit.
* Limit checking is disabled by setting zil_slog_limit to UINT64_MAX.
*/
uint64_t zil_slog_limit = 1024 * 1024;
SYSCTL_QUAD(_vfs_zfs, OID_AUTO, zil_slog_limit, CTLFLAG_RWTUN,
&zil_slog_limit, 0, "Maximal commit size to use SLOG");
#define USE_SLOG(zilog) (((zilog)->zl_logbias == ZFS_LOGBIAS_LATENCY) && \
(((zilog)->zl_cur_used < zil_slog_limit) || \
((zilog)->zl_itx_list_sz < (zil_slog_limit << 1))))
/*
* Start a log block write and advance to the next log block.
* Calls are serialized.
@ -943,6 +947,7 @@ zil_lwb_write_start(zilog_t *zilog, lwb_t *lwb)
uint64_t txg;
uint64_t zil_blksz, wsz;
int i, error;
boolean_t slog;
if (BP_GET_CHECKSUM(&lwb->lwb_blk) == ZIO_CHECKSUM_ZILOG2) {
zilc = (zil_chain_t *)lwb->lwb_buf;
@ -999,8 +1004,7 @@ zil_lwb_write_start(zilog_t *zilog, lwb_t *lwb)
BP_ZERO(bp);
/* pass the old blkptr in order to spread log blocks across devs */
error = zio_alloc_zil(spa, txg, bp, &lwb->lwb_blk, zil_blksz,
USE_SLOG(zilog));
error = zio_alloc_zil(spa, txg, bp, &lwb->lwb_blk, zil_blksz, &slog);
if (error == 0) {
ASSERT3U(bp->blk_birth, ==, txg);
bp->blk_cksum = lwb->lwb_blk.blk_cksum;
@ -1009,7 +1013,7 @@ zil_lwb_write_start(zilog_t *zilog, lwb_t *lwb)
/*
* Allocate a new log write buffer (lwb).
*/
nlwb = zil_alloc_lwb(zilog, bp, txg);
nlwb = zil_alloc_lwb(zilog, bp, slog, txg);
/* Record the block for later vdev flushing */
zil_add_block(zilog, &lwb->lwb_blk);
@ -1046,12 +1050,13 @@ zil_lwb_write_start(zilog_t *zilog, lwb_t *lwb)
static lwb_t *
zil_lwb_commit(zilog_t *zilog, itx_t *itx, lwb_t *lwb)
{
lr_t *lrc = &itx->itx_lr; /* common log record */
lr_write_t *lrw = (lr_write_t *)lrc;
lr_t *lrcb, *lrc = &itx->itx_lr; /* common log record */
lr_write_t *lrwb, *lrw = (lr_write_t *)lrc;
char *lr_buf;
uint64_t txg = lrc->lrc_txg;
uint64_t reclen = lrc->lrc_reclen;
uint64_t dlen = 0;
uint64_t dnow, lwb_sp;
if (lwb == NULL)
return (NULL);
@ -1068,25 +1073,30 @@ zil_lwb_commit(zilog_t *zilog, itx_t *itx, lwb_t *lwb)
zil_lwb_write_init(zilog, lwb);
cont:
/*
* If this record won't fit in the current log block, start a new one.
* For WR_NEED_COPY optimize layout for minimal number of chunks, but
* try to keep wasted space withing reasonable range (12%).
*/
if (lwb->lwb_nused + reclen + dlen > lwb->lwb_sz) {
lwb_sp = lwb->lwb_sz - lwb->lwb_nused;
if (reclen > lwb_sp || (reclen + dlen > lwb_sp &&
lwb_sp < ZIL_MAX_LOG_DATA / 8 && (dlen % ZIL_MAX_LOG_DATA == 0 ||
lwb_sp < reclen + dlen % ZIL_MAX_LOG_DATA))) {
lwb = zil_lwb_write_start(zilog, lwb);
if (lwb == NULL)
return (NULL);
zil_lwb_write_init(zilog, lwb);
ASSERT(LWB_EMPTY(lwb));
if (lwb->lwb_nused + reclen + dlen > lwb->lwb_sz) {
txg_wait_synced(zilog->zl_dmu_pool, txg);
return (lwb);
}
lwb_sp = lwb->lwb_sz - lwb->lwb_nused;
ASSERT3U(reclen + MIN(dlen, sizeof(uint64_t)), <=, lwb_sp);
}
dnow = MIN(dlen, lwb_sp - reclen);
lr_buf = lwb->lwb_buf + lwb->lwb_nused;
bcopy(lrc, lr_buf, reclen);
lrc = (lr_t *)lr_buf;
lrw = (lr_write_t *)lrc;
lrcb = (lr_t *)lr_buf;
lrwb = (lr_write_t *)lrcb;
/*
* If it's a write, fetch the data or get its blkptr as appropriate.
@ -1098,16 +1108,19 @@ zil_lwb_commit(zilog_t *zilog, itx_t *itx, lwb_t *lwb)
char *dbuf;
int error;
if (dlen) {
ASSERT(itx->itx_wr_state == WR_NEED_COPY);
if (itx->itx_wr_state == WR_NEED_COPY) {
dbuf = lr_buf + reclen;
lrw->lr_common.lrc_reclen += dlen;
lrcb->lrc_reclen += dnow;
if (lrwb->lr_length > dnow)
lrwb->lr_length = dnow;
lrw->lr_offset += dnow;
lrw->lr_length -= dnow;
} else {
ASSERT(itx->itx_wr_state == WR_INDIRECT);
dbuf = NULL;
}
error = zilog->zl_get_data(
itx->itx_private, lrw, dbuf, lwb->lwb_zio);
itx->itx_private, lrwb, dbuf, lwb->lwb_zio);
if (error == EIO) {
txg_wait_synced(zilog->zl_dmu_pool, txg);
return (lwb);
@ -1126,12 +1139,18 @@ zil_lwb_commit(zilog_t *zilog, itx_t *itx, lwb_t *lwb)
* equal to the itx sequence number because not all transactions
* are synchronous, and sometimes spa_sync() gets there first.
*/
lrc->lrc_seq = ++zilog->zl_lr_seq; /* we are single threaded */
lwb->lwb_nused += reclen + dlen;
lrcb->lrc_seq = ++zilog->zl_lr_seq; /* we are single threaded */
lwb->lwb_nused += reclen + dnow;
lwb->lwb_max_txg = MAX(lwb->lwb_max_txg, txg);
ASSERT3U(lwb->lwb_nused, <=, lwb->lwb_sz);
ASSERT0(P2PHASE(lwb->lwb_nused, sizeof (uint64_t)));
dlen -= dnow;
if (dlen > 0) {
zilog->zl_cur_used += reclen;
goto cont;
}
return (lwb);
}
@ -1145,7 +1164,6 @@ zil_itx_create(uint64_t txtype, size_t lrsize)
itx = kmem_alloc(offsetof(itx_t, itx_lr) + lrsize, KM_SLEEP);
itx->itx_lr.lrc_txtype = txtype;
itx->itx_lr.lrc_reclen = lrsize;
itx->itx_sod = lrsize; /* if write & WR_NEED_COPY will be increased */
itx->itx_lr.lrc_seq = 0; /* defensive */
itx->itx_sync = B_TRUE; /* default is synchronous */
@ -1294,11 +1312,8 @@ zil_itx_assign(zilog_t *zilog, itx_t *itx, dmu_tx_t *tx)
* this itxg. Save the itxs for release below.
* This should be rare.
*/
atomic_add_64(&zilog->zl_itx_list_sz, -itxg->itxg_sod);
itxg->itxg_sod = 0;
clean = itxg->itxg_itxs;
}
ASSERT(itxg->itxg_sod == 0);
itxg->itxg_txg = txg;
itxs = itxg->itxg_itxs = kmem_zalloc(sizeof (itxs_t), KM_SLEEP);
@ -1310,8 +1325,6 @@ zil_itx_assign(zilog_t *zilog, itx_t *itx, dmu_tx_t *tx)
}
if (itx->itx_sync) {
list_insert_tail(&itxs->i_sync_list, itx);
atomic_add_64(&zilog->zl_itx_list_sz, itx->itx_sod);
itxg->itxg_sod += itx->itx_sod;
} else {
avl_tree_t *t = &itxs->i_async_tree;
uint64_t foid = ((lr_ooo_t *)&itx->itx_lr)->lr_foid;
@ -1359,8 +1372,6 @@ zil_clean(zilog_t *zilog, uint64_t synced_txg)
ASSERT3U(itxg->itxg_txg, <=, synced_txg);
ASSERT(itxg->itxg_txg != 0);
ASSERT(zilog->zl_clean_taskq != NULL);
atomic_add_64(&zilog->zl_itx_list_sz, -itxg->itxg_sod);
itxg->itxg_sod = 0;
clean_me = itxg->itxg_itxs;
itxg->itxg_itxs = NULL;
itxg->itxg_txg = 0;
@ -1384,7 +1395,6 @@ zil_get_commit_list(zilog_t *zilog)
{
uint64_t otxg, txg;
list_t *commit_list = &zilog->zl_itx_commit_list;
uint64_t push_sod = 0;
if (spa_freeze_txg(zilog->zl_spa) != UINT64_MAX) /* ziltest support */
otxg = ZILTEST_TXG;
@ -1401,12 +1411,9 @@ zil_get_commit_list(zilog_t *zilog)
}
list_move_tail(commit_list, &itxg->itxg_itxs->i_sync_list);
push_sod += itxg->itxg_sod;
itxg->itxg_sod = 0;
mutex_exit(&itxg->itxg_lock);
}
atomic_add_64(&zilog->zl_itx_list_sz, -push_sod);
}
/*

15
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zio.c
View File

@ -2908,20 +2908,21 @@ zio_dva_unallocate(zio_t *zio, zio_gang_node_t *gn, blkptr_t *bp)
*/
int
zio_alloc_zil(spa_t *spa, uint64_t txg, blkptr_t *new_bp, blkptr_t *old_bp,
uint64_t size, boolean_t use_slog)
uint64_t size, boolean_t *slog)
{
int error = 1;
ASSERT(txg > spa_syncing_txg(spa));
if (use_slog) {
error = metaslab_alloc(spa, spa_log_class(spa), size,
new_bp, 1, txg, old_bp, METASLAB_HINTBP_AVOID, NULL);
}
if (error) {
error = metaslab_alloc(spa, spa_log_class(spa), size,
new_bp, 1, txg, old_bp, METASLAB_HINTBP_AVOID, NULL);
if (error == 0) {
*slog = TRUE;
} else {
error = metaslab_alloc(spa, spa_normal_class(spa), size,
new_bp, 1, txg, old_bp, METASLAB_HINTBP_AVOID, NULL);
if (error == 0)
*slog = FALSE;
}
if (error == 0) {

50
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c
View File

@ -1387,54 +1387,44 @@ zvol_log_write(zvol_state_t *zv, dmu_tx_t *tx, offset_t off, ssize_t resid,
{
uint32_t blocksize = zv->zv_volblocksize;
zilog_t *zilog = zv->zv_zilog;
boolean_t slogging;
ssize_t immediate_write_sz;
itx_wr_state_t write_state;
if (zil_replaying(zilog, tx))
return;
immediate_write_sz = (zilog->zl_logbias == ZFS_LOGBIAS_THROUGHPUT)
? 0 : zvol_immediate_write_sz;
slogging = spa_has_slogs(zilog->zl_spa) &&
(zilog->zl_logbias == ZFS_LOGBIAS_LATENCY);
if (zilog->zl_logbias == ZFS_LOGBIAS_THROUGHPUT)
write_state = WR_INDIRECT;
else if (!spa_has_slogs(zilog->zl_spa) &&
resid >= blocksize && blocksize > zvol_immediate_write_sz)
write_state = WR_INDIRECT;
else if (sync)
write_state = WR_COPIED;
else
write_state = WR_NEED_COPY;
while (resid) {
itx_t *itx;
lr_write_t *lr;
ssize_t len;
itx_wr_state_t write_state;
itx_wr_state_t wr_state = write_state;
ssize_t len = resid;
/*
* Unlike zfs_log_write() we can be called with
* upto DMU_MAX_ACCESS/2 (5MB) writes.
*/
if (blocksize > immediate_write_sz && !slogging &&
resid >= blocksize && off % blocksize == 0) {
write_state = WR_INDIRECT; /* uses dmu_sync */
len = blocksize;
} else if (sync) {
write_state = WR_COPIED;
len = MIN(ZIL_MAX_LOG_DATA, resid);
} else {
write_state = WR_NEED_COPY;
len = MIN(ZIL_MAX_LOG_DATA, resid);
}
if (wr_state == WR_COPIED && resid > ZIL_MAX_COPIED_DATA)
wr_state = WR_NEED_COPY;
else if (wr_state == WR_INDIRECT)
len = MIN(blocksize - P2PHASE(off, blocksize), resid);
itx = zil_itx_create(TX_WRITE, sizeof (*lr) +
(write_state == WR_COPIED ? len : 0));
(wr_state == WR_COPIED ? len : 0));
lr = (lr_write_t *)&itx->itx_lr;
if (write_state == WR_COPIED && dmu_read(zv->zv_objset,
if (wr_state == WR_COPIED && dmu_read(zv->zv_objset,
ZVOL_OBJ, off, len, lr + 1, DMU_READ_NO_PREFETCH) != 0) {
zil_itx_destroy(itx);
itx = zil_itx_create(TX_WRITE, sizeof (*lr));
lr = (lr_write_t *)&itx->itx_lr;
write_state = WR_NEED_COPY;
wr_state = WR_NEED_COPY;
}
itx->itx_wr_state = write_state;
if (write_state == WR_NEED_COPY)
itx->itx_sod += len;
itx->itx_wr_state = wr_state;
lr->lr_foid = ZVOL_OBJ;
lr->lr_offset = off;
lr->lr_length = len;