diff options
Diffstat (limited to 'module/zfs/zfs_vnops.c')
| -rw-r--r-- | module/zfs/zfs_vnops.c | 32 |
1 files changed, 15 insertions, 17 deletions
diff --git a/module/zfs/zfs_vnops.c b/module/zfs/zfs_vnops.c index abf3747db..1552b61e0 100644 --- a/module/zfs/zfs_vnops.c +++ b/module/zfs/zfs_vnops.c @@ -106,11 +106,18 @@ * (3) All range locks must be grabbed before calling dmu_tx_assign(), * as they can span dmu_tx_assign() calls. * - * (4) Always pass TXG_NOWAIT as the second argument to dmu_tx_assign(). - * This is critical because we don't want to block while holding locks. - * Note, in particular, that if a lock is sometimes acquired before - * the tx assigns, and sometimes after (e.g. z_lock), then failing to - * use a non-blocking assign can deadlock the system. The scenario: + * (4) If ZPL locks are held, pass TXG_NOWAIT as the second argument to + * dmu_tx_assign(). This is critical because we don't want to block + * while holding locks. + * + * If no ZPL locks are held (aside from ZFS_ENTER()), use TXG_WAIT. This + * reduces lock contention and CPU usage when we must wait (note that if + * throughput is constrained by the storage, nearly every transaction + * must wait). + * + * Note, in particular, that if a lock is sometimes acquired before + * the tx assigns, and sometimes after (e.g. z_lock), then failing + * to use a non-blocking assign can deadlock the system. The scenario: * * Thread A has grabbed a lock before calling dmu_tx_assign(). * Thread B is in an already-assigned tx, and blocks for this lock. @@ -712,7 +719,6 @@ zfs_write(struct inode *ip, uio_t *uio, int ioflag, cred_t *cr) while (n > 0) { abuf = NULL; woff = uio->uio_loffset; -again: if (zfs_owner_overquota(zsb, zp, B_FALSE) || zfs_owner_overquota(zsb, zp, B_TRUE)) { if (abuf != NULL) @@ -762,13 +768,8 @@ again: dmu_tx_hold_sa(tx, zp->z_sa_hdl, B_FALSE); dmu_tx_hold_write(tx, zp->z_id, woff, MIN(n, max_blksz)); zfs_sa_upgrade_txholds(tx, zp); - error = dmu_tx_assign(tx, TXG_NOWAIT); + error = dmu_tx_assign(tx, TXG_WAIT); if (error) { - if (error == ERESTART) { - dmu_tx_wait(tx); - dmu_tx_abort(tx); - goto again; - } dmu_tx_abort(tx); if (abuf != NULL) dmu_return_arcbuf(abuf); @@ -2833,12 +2834,9 @@ top: zfs_sa_upgrade_txholds(tx, zp); - err = dmu_tx_assign(tx, TXG_NOWAIT); - if (err) { - if (err == ERESTART) - dmu_tx_wait(tx); + err = dmu_tx_assign(tx, TXG_WAIT); + if (err) goto out; - } count = 0; /* |