diff options
| -rw-r--r-- | module/os/linux/zfs/zfs_vnops_os.c | 34 |
1 files changed, 22 insertions, 12 deletions
diff --git a/module/os/linux/zfs/zfs_vnops_os.c b/module/os/linux/zfs/zfs_vnops_os.c index 15b7f019c..0587dd7cc 100644 --- a/module/os/linux/zfs/zfs_vnops_os.c +++ b/module/os/linux/zfs/zfs_vnops_os.c @@ -87,15 +87,18 @@ * must be checked with ZFS_VERIFY_ZP(zp). Both of these macros * can return EIO from the calling function. * - * (2) zrele() should always be the last thing except for zil_commit() - * (if necessary) and ZFS_EXIT(). This is for 3 reasons: - * First, if it's the last reference, the vnode/znode - * can be freed, so the zp may point to freed memory. Second, the last - * reference will call zfs_zinactive(), which may induce a lot of work -- - * pushing cached pages (which acquires range locks) and syncing out - * cached atime changes. Third, zfs_zinactive() may require a new tx, - * which could deadlock the system if you were already holding one. - * If you must call zrele() within a tx then use zfs_zrele_async(). + * (2) zrele() should always be the last thing except for zil_commit() (if + * necessary) and ZFS_EXIT(). This is for 3 reasons: First, if it's the + * last reference, the vnode/znode can be freed, so the zp may point to + * freed memory. Second, the last reference will call zfs_zinactive(), + * which may induce a lot of work -- pushing cached pages (which acquires + * range locks) and syncing out cached atime changes. Third, + * zfs_zinactive() may require a new tx, which could deadlock the system + * if you were already holding one. This deadlock occurs because the tx + * currently being operated on prevents a txg from syncing, which + * prevents the new tx from progressing, resulting in a deadlock. If you + * must call zrele() within a tx, use zfs_zrele_async(). Note that iput() + * is a synonym for zrele(). * * (3) All range locks must be grabbed before calling dmu_tx_assign(), * as they can span dmu_tx_assign() calls. @@ -398,11 +401,18 @@ zfs_zrele_async(znode_t *zp) ASSERT(atomic_read(&ip->i_count) > 0); ASSERT(os != NULL); - if (atomic_read(&ip->i_count) == 1) + /* + * If decrementing the count would put us at 0, we can't do it inline + * here, because that would be synchronous. Instead, dispatch an iput + * to run later. + * + * For more information on the dangers of a synchronous iput, see the + * header comment of this file. + */ + if (!atomic_add_unless(&ip->i_count, -1, 1)) { VERIFY(taskq_dispatch(dsl_pool_zrele_taskq(dmu_objset_pool(os)), (task_func_t *)iput, ip, TQ_SLEEP) != TASKQID_INVALID); - else - zrele(zp); + } } |