/* * CDDL HEADER START * * The contents of this file are subject to the terms of the * Common Development and Distribution License (the "License"). * You may not use this file except in compliance with the License. * * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE * or http://www.opensolaris.org/os/licensing. * See the License for the specific language governing permissions * and limitations under the License. * * When distributing Covered Code, include this CDDL HEADER in each * file and include the License file at usr/src/OPENSOLARIS.LICENSE. * If applicable, add the following below this CDDL HEADER, with the * fields enclosed by brackets "[]" replaced with your own identifying * information: Portions Copyright [yyyy] [name of copyright owner] * * CDDL HEADER END */ /* * Copyright (C) 2008-2010 Lawrence Livermore National Security, LLC. * Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER). * Rewritten for Linux by Brian Behlendorf . * LLNL-CODE-403049. * * ZFS volume emulation driver. * * Makes a DMU object look like a volume of arbitrary size, up to 2^64 bytes. * Volumes are accessed through the symbolic links named: * * /dev// * * Volumes are persistent through reboot and module load. No user command * needs to be run before opening and using a device. * * Copyright 2014 Nexenta Systems, Inc. All rights reserved. * Copyright (c) 2016 Actifio, Inc. All rights reserved. * Copyright (c) 2012, 2017 by Delphix. All rights reserved. */ /* * Note on locking of zvol state structures. * * These structures are used to maintain internal state used to emulate block * devices on top of zvols. In particular, management of device minor number * operations - create, remove, rename, and set_snapdev - involves access to * these structures. The zvol_state_lock is primarily used to protect the * zvol_state_list. The zv->zv_state_lock is used to protect the contents * of the zvol_state_t structures, as well as to make sure that when the * time comes to remove the structure from the list, it is not in use, and * therefore, it can be taken off zvol_state_list and freed. * * The zv_suspend_lock was introduced to allow for suspending I/O to a zvol, * e.g. for the duration of receive and rollback operations. This lock can be * held for significant periods of time. Given that it is undesirable to hold * mutexes for long periods of time, the following lock ordering applies: * - take zvol_state_lock if necessary, to protect zvol_state_list * - take zv_suspend_lock if necessary, by the code path in question * - take zv_state_lock to protect zvol_state_t * * The minor operations are issued to spa->spa_zvol_taskq queues, that are * single-threaded (to preserve order of minor operations), and are executed * through the zvol_task_cb that dispatches the specific operations. Therefore, * these operations are serialized per pool. Consequently, we can be certain * that for a given zvol, there is only one operation at a time in progress. * That is why one can be sure that first, zvol_state_t for a given zvol is * allocated and placed on zvol_state_list, and then other minor operations * for this zvol are going to proceed in the order of issue. * * It is also worth keeping in mind that once add_disk() is called, the zvol is * announced to the world, and zvol_open()/zvol_release() can be called at any * time. Incidentally, add_disk() itself calls zvol_open()->zvol_first_open() * and zvol_release()->zvol_last_close() directly as well. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include unsigned int zvol_inhibit_dev = 0; unsigned int zvol_major = ZVOL_MAJOR; unsigned int zvol_threads = 32; unsigned int zvol_request_sync = 0; unsigned int zvol_prefetch_bytes = (128 * 1024); unsigned long zvol_max_discard_blocks = 16384; static taskq_t *zvol_taskq; static kmutex_t zvol_state_lock; static list_t zvol_state_list; #define ZVOL_HT_SIZE 1024 static struct hlist_head *zvol_htable; #define ZVOL_HT_HEAD(hash) (&zvol_htable[(hash) & (ZVOL_HT_SIZE-1)]) static struct ida zvol_ida; /* * The in-core state of each volume. */ struct zvol_state { char zv_name[MAXNAMELEN]; /* name */ uint64_t zv_volsize; /* advertised space */ uint64_t zv_volblocksize; /* volume block size */ objset_t *zv_objset; /* objset handle */ uint32_t zv_flags; /* ZVOL_* flags */ uint32_t zv_open_count; /* open counts */ uint32_t zv_changed; /* disk changed */ zilog_t *zv_zilog; /* ZIL handle */ zfs_rlock_t zv_range_lock; /* range lock */ dnode_t *zv_dn; /* dnode hold */ dev_t zv_dev; /* device id */ struct gendisk *zv_disk; /* generic disk */ struct request_queue *zv_queue; /* request queue */ list_node_t zv_next; /* next zvol_state_t linkage */ uint64_t zv_hash; /* name hash */ struct hlist_node zv_hlink; /* hash link */ kmutex_t zv_state_lock; /* protects zvol_state_t */ atomic_t zv_suspend_ref; /* refcount for suspend */ krwlock_t zv_suspend_lock; /* suspend lock */ }; typedef enum { ZVOL_ASYNC_CREATE_MINORS, ZVOL_ASYNC_REMOVE_MINORS, ZVOL_ASYNC_RENAME_MINORS, ZVOL_ASYNC_SET_SNAPDEV, ZVOL_ASYNC_MAX } zvol_async_op_t; typedef struct { zvol_async_op_t op; char pool[MAXNAMELEN]; char name1[MAXNAMELEN]; char name2[MAXNAMELEN]; zprop_source_t source; uint64_t snapdev; } zvol_task_t; #define ZVOL_RDONLY 0x1 static uint64_t zvol_name_hash(const char *name) { int i; uint64_t crc = -1ULL; uint8_t *p = (uint8_t *)name; ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); for (i = 0; i < MAXNAMELEN - 1 && *p; i++, p++) { crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ (*p)) & 0xFF]; } return (crc); } /* * Find a zvol_state_t given the full major+minor dev_t. If found, * return with zv_state_lock taken, otherwise, return (NULL) without * taking zv_state_lock. */ static zvol_state_t * zvol_find_by_dev(dev_t dev) { zvol_state_t *zv; mutex_enter(&zvol_state_lock); for (zv = list_head(&zvol_state_list); zv != NULL; zv = list_next(&zvol_state_list, zv)) { mutex_enter(&zv->zv_state_lock); if (zv->zv_dev == dev) { mutex_exit(&zvol_state_lock); return (zv); } mutex_exit(&zv->zv_state_lock); } mutex_exit(&zvol_state_lock); return (NULL); } /* * Find a zvol_state_t given the name and hash generated by zvol_name_hash. * If found, return with zv_suspend_lock and zv_state_lock taken, otherwise, * return (NULL) without the taking locks. The zv_suspend_lock is always taken * before zv_state_lock. The mode argument indicates the mode (including none) * for zv_suspend_lock to be taken. */ static zvol_state_t * zvol_find_by_name_hash(const char *name, uint64_t hash, int mode) { zvol_state_t *zv; struct hlist_node *p; mutex_enter(&zvol_state_lock); hlist_for_each(p, ZVOL_HT_HEAD(hash)) { zv = hlist_entry(p, zvol_state_t, zv_hlink); mutex_enter(&zv->zv_state_lock); if (zv->zv_hash == hash && strncmp(zv->zv_name, name, MAXNAMELEN) == 0) { /* * this is the right zvol, take the locks in the * right order */ if (mode != RW_NONE && !rw_tryenter(&zv->zv_suspend_lock, mode)) { mutex_exit(&zv->zv_state_lock); rw_enter(&zv->zv_suspend_lock, mode); mutex_enter(&zv->zv_state_lock); /* * zvol cannot be renamed as we continue * to hold zvol_state_lock */ ASSERT(zv->zv_hash == hash && strncmp(zv->zv_name, name, MAXNAMELEN) == 0); } mutex_exit(&zvol_state_lock); return (zv); } mutex_exit(&zv->zv_state_lock); } mutex_exit(&zvol_state_lock); return (NULL); } /* * Find a zvol_state_t given the name. * If found, return with zv_suspend_lock and zv_state_lock taken, otherwise, * return (NULL) without the taking locks. The zv_suspend_lock is always taken * before zv_state_lock. The mode argument indicates the mode (including none) * for zv_suspend_lock to be taken. */ static zvol_state_t * zvol_find_by_name(const char *name, int mode) { return (zvol_find_by_name_hash(name, zvol_name_hash(name), mode)); } /* * Given a path, return TRUE if path is a ZVOL. */ boolean_t zvol_is_zvol(const char *device) { struct block_device *bdev; unsigned int major; bdev = vdev_lookup_bdev(device); if (IS_ERR(bdev)) return (B_FALSE); major = MAJOR(bdev->bd_dev); bdput(bdev); if (major == zvol_major) return (B_TRUE); return (B_FALSE); } /* * ZFS_IOC_CREATE callback handles dmu zvol and zap object creation. */ void zvol_create_cb(objset_t *os, void *arg, cred_t *cr, dmu_tx_t *tx) { zfs_creat_t *zct = arg; nvlist_t *nvprops = zct->zct_props; int error; uint64_t volblocksize, volsize; VERIFY(nvlist_lookup_uint64(nvprops, zfs_prop_to_name(ZFS_PROP_VOLSIZE), &volsize) == 0); if (nvlist_lookup_uint64(nvprops, zfs_prop_to_name(ZFS_PROP_VOLBLOCKSIZE), &volblocksize) != 0) volblocksize = zfs_prop_default_numeric(ZFS_PROP_VOLBLOCKSIZE); /* * These properties must be removed from the list so the generic * property setting step won't apply to them. */ VERIFY(nvlist_remove_all(nvprops, zfs_prop_to_name(ZFS_PROP_VOLSIZE)) == 0); (void) nvlist_remove_all(nvprops, zfs_prop_to_name(ZFS_PROP_VOLBLOCKSIZE)); error = dmu_object_claim(os, ZVOL_OBJ, DMU_OT_ZVOL, volblocksize, DMU_OT_NONE, 0, tx); ASSERT(error == 0); error = zap_create_claim(os, ZVOL_ZAP_OBJ, DMU_OT_ZVOL_PROP, DMU_OT_NONE, 0, tx); ASSERT(error == 0); error = zap_update(os, ZVOL_ZAP_OBJ, "size", 8, 1, &volsize, tx); ASSERT(error == 0); } /* * ZFS_IOC_OBJSET_STATS entry point. */ int zvol_get_stats(objset_t *os, nvlist_t *nv) { int error; dmu_object_info_t *doi; uint64_t val; error = zap_lookup(os, ZVOL_ZAP_OBJ, "size", 8, 1, &val); if (error) return (SET_ERROR(error)); dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_VOLSIZE, val); doi = kmem_alloc(sizeof (dmu_object_info_t), KM_SLEEP); error = dmu_object_info(os, ZVOL_OBJ, doi); if (error == 0) { dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_VOLBLOCKSIZE, doi->doi_data_block_size); } kmem_free(doi, sizeof (dmu_object_info_t)); return (SET_ERROR(error)); } static void zvol_size_changed(zvol_state_t *zv, uint64_t volsize) { struct block_device *bdev; ASSERT(MUTEX_HELD(&zv->zv_state_lock)); bdev = bdget_disk(zv->zv_disk, 0); if (bdev == NULL) return; set_capacity(zv->zv_disk, volsize >> 9); zv->zv_volsize = volsize; check_disk_size_change(zv->zv_disk, bdev); bdput(bdev); } /* * Sanity check volume size. */ int zvol_check_volsize(uint64_t volsize, uint64_t blocksize) { if (volsize == 0) return (SET_ERROR(EINVAL)); if (volsize % blocksize != 0) return (SET_ERROR(EINVAL)); #ifdef _ILP32 if (volsize - 1 > SPEC_MAXOFFSET_T) return (SET_ERROR(EOVERFLOW)); #endif return (0); } /* * Ensure the zap is flushed then inform the VFS of the capacity change. */ static int zvol_update_volsize(uint64_t volsize, objset_t *os) { dmu_tx_t *tx; int error; uint64_t txg; tx = dmu_tx_create(os); dmu_tx_hold_zap(tx, ZVOL_ZAP_OBJ, TRUE, NULL); dmu_tx_mark_netfree(tx); error = dmu_tx_assign(tx, TXG_WAIT); if (error) { dmu_tx_abort(tx); return (SET_ERROR(error)); } txg = dmu_tx_get_txg(tx); error = zap_update(os, ZVOL_ZAP_OBJ, "size", 8, 1, &volsize, tx); dmu_tx_commit(tx); txg_wait_synced(dmu_objset_pool(os), txg); if (error == 0) error = dmu_free_long_range(os, ZVOL_OBJ, volsize, DMU_OBJECT_END); return (error); } static int zvol_update_live_volsize(zvol_state_t *zv, uint64_t volsize) { zvol_size_changed(zv, volsize); /* * We should post a event here describing the expansion. However, * the zfs_ereport_post() interface doesn't nicely support posting * events for zvols, it assumes events relate to vdevs or zios. */ return (0); } /* * Set ZFS_PROP_VOLSIZE set entry point. */ int zvol_set_volsize(const char *name, uint64_t volsize) { zvol_state_t *zv = NULL; objset_t *os = NULL; int error; dmu_object_info_t *doi; uint64_t readonly; boolean_t owned = B_FALSE; error = dsl_prop_get_integer(name, zfs_prop_to_name(ZFS_PROP_READONLY), &readonly, NULL); if (error != 0) return (SET_ERROR(error)); if (readonly) return (SET_ERROR(EROFS)); zv = zvol_find_by_name(name, RW_READER); ASSERT(zv == NULL || (MUTEX_HELD(&zv->zv_state_lock) && RW_READ_HELD(&zv->zv_suspend_lock))); if (zv == NULL || zv->zv_objset == NULL) { if (zv != NULL) rw_exit(&zv->zv_suspend_lock); if ((error = dmu_objset_own(name, DMU_OST_ZVOL, B_FALSE, FTAG, &os)) != 0) { if (zv != NULL) mutex_exit(&zv->zv_state_lock); return (SET_ERROR(error)); } owned = B_TRUE; if (zv != NULL) zv->zv_objset = os; } else { os = zv->zv_objset; } doi = kmem_alloc(sizeof (dmu_object_info_t), KM_SLEEP); if ((error = dmu_object_info(os, ZVOL_OBJ, doi)) || (error = zvol_check_volsize(volsize, doi->doi_data_block_size))) goto out; error = zvol_update_volsize(volsize, os); if (error == 0 && zv != NULL) error = zvol_update_live_volsize(zv, volsize); out: kmem_free(doi, sizeof (dmu_object_info_t)); if (owned) { dmu_objset_disown(os, FTAG); if (zv != NULL) zv->zv_objset = NULL; } else { rw_exit(&zv->zv_suspend_lock); } if (zv != NULL) mutex_exit(&zv->zv_state_lock); return (SET_ERROR(error)); } /* * Sanity check volume block size. */ int zvol_check_volblocksize(const char *name, uint64_t volblocksize) { /* Record sizes above 128k need the feature to be enabled */ if (volblocksize > SPA_OLD_MAXBLOCKSIZE) { spa_t *spa; int error; if ((error = spa_open(name, &spa, FTAG)) != 0) return (error); if (!spa_feature_is_enabled(spa, SPA_FEATURE_LARGE_BLOCKS)) { spa_close(spa, FTAG); return (SET_ERROR(ENOTSUP)); } /* * We don't allow setting the property above 1MB, * unless the tunable has been changed. */ if (volblocksize > zfs_max_recordsize) return (SET_ERROR(EDOM)); spa_close(spa, FTAG); } if (volblocksize < SPA_MINBLOCKSIZE || volblocksize > SPA_MAXBLOCKSIZE || !ISP2(volblocksize)) return (SET_ERROR(EDOM)); return (0); } /* * Set ZFS_PROP_VOLBLOCKSIZE set entry point. */ int zvol_set_volblocksize(const char *name, uint64_t volblocksize) { zvol_state_t *zv; dmu_tx_t *tx; int error; zv = zvol_find_by_name(name, RW_READER); if (zv == NULL) return (SET_ERROR(ENXIO)); ASSERT(MUTEX_HELD(&zv->zv_state_lock) && RW_READ_HELD(&zv->zv_suspend_lock)); if (zv->zv_flags & ZVOL_RDONLY) { mutex_exit(&zv->zv_state_lock); rw_exit(&zv->zv_suspend_lock); return (SET_ERROR(EROFS)); } tx = dmu_tx_create(zv->zv_objset); dmu_tx_hold_bonus(tx, ZVOL_OBJ); error = dmu_tx_assign(tx, TXG_WAIT); if (error) { dmu_tx_abort(tx); } else { error = dmu_object_set_blocksize(zv->zv_objset, ZVOL_OBJ, volblocksize, 0, tx); if (error == ENOTSUP) error = SET_ERROR(EBUSY); dmu_tx_commit(tx); if (error == 0) zv->zv_volblocksize = volblocksize; } mutex_exit(&zv->zv_state_lock); rw_exit(&zv->zv_suspend_lock); return (SET_ERROR(error)); } /* * Replay a TX_TRUNCATE ZIL transaction if asked. TX_TRUNCATE is how we * implement DKIOCFREE/free-long-range. */ static int zvol_replay_truncate(zvol_state_t *zv, lr_truncate_t *lr, boolean_t byteswap) { uint64_t offset, length; if (byteswap) byteswap_uint64_array(lr, sizeof (*lr)); offset = lr->lr_offset; length = lr->lr_length; return (dmu_free_long_range(zv->zv_objset, ZVOL_OBJ, offset, length)); } /* * Replay a TX_WRITE ZIL transaction that didn't get committed * after a system failure */ static int zvol_replay_write(zvol_state_t *zv, lr_write_t *lr, boolean_t byteswap) { objset_t *os = zv->zv_objset; char *data = (char *)(lr + 1); /* data follows lr_write_t */ uint64_t off = lr->lr_offset; uint64_t len = lr->lr_length; dmu_tx_t *tx; int error; if (byteswap) byteswap_uint64_array(lr, sizeof (*lr)); tx = dmu_tx_create(os); dmu_tx_hold_write(tx, ZVOL_OBJ, off, len); error = dmu_tx_assign(tx, TXG_WAIT); if (error) { dmu_tx_abort(tx); } else { dmu_write(os, ZVOL_OBJ, off, len, data, tx); dmu_tx_commit(tx); } return (SET_ERROR(error)); } static int zvol_replay_err(zvol_state_t *zv, lr_t *lr, boolean_t byteswap) { return (SET_ERROR(ENOTSUP)); } /* * Callback vectors for replaying records. * Only TX_WRITE and TX_TRUNCATE are needed for zvol. */ zil_replay_func_t zvol_replay_vector[TX_MAX_TYPE] = { (zil_replay_func_t)zvol_replay_err, /* no such transaction type */ (zil_replay_func_t)zvol_replay_err, /* TX_CREATE */ (zil_replay_func_t)zvol_replay_err, /* TX_MKDIR */ (zil_replay_func_t)zvol_replay_err, /* TX_MKXATTR */ (zil_replay_func_t)zvol_replay_err, /* TX_SYMLINK */ (zil_replay_func_t)zvol_replay_err, /* TX_REMOVE */ (zil_replay_func_t)zvol_replay_err, /* TX_RMDIR */ (zil_replay_func_t)zvol_replay_err, /* TX_LINK */ (zil_replay_func_t)zvol_replay_err, /* TX_RENAME */ (zil_replay_func_t)zvol_replay_write, /* TX_WRITE */ (zil_replay_func_t)zvol_replay_truncate, /* TX_TRUNCATE */ (zil_replay_func_t)zvol_replay_err, /* TX_SETATTR */ (zil_replay_func_t)zvol_replay_err, /* TX_ACL */ }; /* * zvol_log_write() handles synchronous writes using TX_WRITE ZIL transactions. * * We store data in the log buffers if it's small enough. * Otherwise we will later flush the data out via dmu_sync(). */ ssize_t zvol_immediate_write_sz = 32768; static void zvol_log_write(zvol_state_t *zv, dmu_tx_t *tx, uint64_t offset, uint64_t size, int sync) { uint32_t blocksize = zv->zv_volblocksize; zilog_t *zilog = zv->zv_zilog; itx_wr_state_t write_state; if (zil_replaying(zilog, tx)) return; if (zilog->zl_logbias == ZFS_LOGBIAS_THROUGHPUT) write_state = WR_INDIRECT; else if (!spa_has_slogs(zilog->zl_spa) && size >= blocksize && blocksize > zvol_immediate_write_sz) write_state = WR_INDIRECT; else if (sync) write_state = WR_COPIED; else write_state = WR_NEED_COPY; while (size) { itx_t *itx; lr_write_t *lr; itx_wr_state_t wr_state = write_state; ssize_t len = size; if (wr_state == WR_COPIED && size > ZIL_MAX_COPIED_DATA) wr_state = WR_NEED_COPY; else if (wr_state == WR_INDIRECT) len = MIN(blocksize - P2PHASE(offset, blocksize), size); itx = zil_itx_create(TX_WRITE, sizeof (*lr) + (wr_state == WR_COPIED ? len : 0)); lr = (lr_write_t *)&itx->itx_lr; if (wr_state == WR_COPIED && dmu_read_by_dnode(zv->zv_dn, offset, 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; wr_state = WR_NEED_COPY; } itx->itx_wr_state = wr_state; lr->lr_foid = ZVOL_OBJ; lr->lr_offset = offset; lr->lr_length = len; lr->lr_blkoff = 0; BP_ZERO(&lr->lr_blkptr); itx->itx_private = zv; itx->itx_sync = sync; (void) zil_itx_assign(zilog, itx, tx); offset += len; size -= len; } } typedef struct zv_request { zvol_state_t *zv; struct bio *bio; rl_t *rl; } zv_request_t; static void uio_from_bio(uio_t *uio, struct bio *bio) { uio->uio_bvec = &bio->bi_io_vec[BIO_BI_IDX(bio)]; uio->uio_skip = BIO_BI_SKIP(bio); uio->uio_resid = BIO_BI_SIZE(bio); uio->uio_iovcnt = bio->bi_vcnt - BIO_BI_IDX(bio); uio->uio_loffset = BIO_BI_SECTOR(bio) << 9; uio->uio_limit = MAXOFFSET_T; uio->uio_segflg = UIO_BVEC; } static void zvol_write(void *arg) { zv_request_t *zvr = arg; struct bio *bio = zvr->bio; uio_t uio; zvol_state_t *zv = zvr->zv; uint64_t volsize = zv->zv_volsize; boolean_t sync; int error = 0; unsigned long start_jif; uio_from_bio(&uio, bio); ASSERT(zv && zv->zv_open_count > 0); start_jif = jiffies; generic_start_io_acct(WRITE, bio_sectors(bio), &zv->zv_disk->part0); sync = bio_is_fua(bio) || zv->zv_objset->os_sync == ZFS_SYNC_ALWAYS; while (uio.uio_resid > 0 && uio.uio_loffset < volsize) { uint64_t bytes = MIN(uio.uio_resid, DMU_MAX_ACCESS >> 1); uint64_t off = uio.uio_loffset; dmu_tx_t *tx = dmu_tx_create(zv->zv_objset); if (bytes > volsize - off) /* don't write past the end */ bytes = volsize - off; dmu_tx_hold_write(tx, ZVOL_OBJ, off, bytes); /* This will only fail for ENOSPC */ error = dmu_tx_assign(tx, TXG_WAIT); if (error) { dmu_tx_abort(tx); break; } error = dmu_write_uio_dnode(zv->zv_dn, &uio, bytes, tx); if (error == 0) zvol_log_write(zv, tx, off, bytes, sync); dmu_tx_commit(tx); if (error) break; } zfs_range_unlock(zvr->rl); if (sync) zil_commit(zv->zv_zilog, ZVOL_OBJ); rw_exit(&zv->zv_suspend_lock); generic_end_io_acct(WRITE, &zv->zv_disk->part0, start_jif); BIO_END_IO(bio, -error); kmem_free(zvr, sizeof (zv_request_t)); } /* * Log a DKIOCFREE/free-long-range to the ZIL with TX_TRUNCATE. */ static void zvol_log_truncate(zvol_state_t *zv, dmu_tx_t *tx, uint64_t off, uint64_t len, boolean_t sync) { itx_t *itx; lr_truncate_t *lr; zilog_t *zilog = zv->zv_zilog; if (zil_replaying(zilog, tx)) return; itx = zil_itx_create(TX_TRUNCATE, sizeof (*lr)); lr = (lr_truncate_t *)&itx->itx_lr; lr->lr_foid = ZVOL_OBJ; lr->lr_offset = off; lr->lr_length = len; itx->itx_sync = sync; zil_itx_assign(zilog, itx, tx); } static void zvol_discard(void *arg) { zv_request_t *zvr = arg; struct bio *bio = zvr->bio; zvol_state_t *zv = zvr->zv; uint64_t start = BIO_BI_SECTOR(bio) << 9; uint64_t size = BIO_BI_SIZE(bio); uint64_t end = start + size; int error = 0; dmu_tx_t *tx; unsigned long start_jif; ASSERT(zv && zv->zv_open_count > 0); start_jif = jiffies; generic_start_io_acct(WRITE, bio_sectors(bio), &zv->zv_disk->part0); if (end > zv->zv_volsize) { error = SET_ERROR(EIO); goto out; } /* * Align the request to volume block boundaries when a secure erase is * not required. This will prevent dnode_free_range() from zeroing out * the unaligned parts which is slow (read-modify-write) and useless * since we are not freeing any space by doing so. */ if (!bio_is_secure_erase(bio)) { start = P2ROUNDUP(start, zv->zv_volblocksize); end = P2ALIGN(end, zv->zv_volblocksize); size = end - start; } if (start >= end) goto out; tx = dmu_tx_create(zv->zv_objset); dmu_tx_mark_netfree(tx); error = dmu_tx_assign(tx, TXG_WAIT); if (error != 0) { dmu_tx_abort(tx); } else { zvol_log_truncate(zv, tx, start, size, B_TRUE); dmu_tx_commit(tx); error = dmu_free_long_range(zv->zv_objset, ZVOL_OBJ, start, size); } out: zfs_range_unlock(zvr->rl); rw_exit(&zv->zv_suspend_lock); generic_end_io_acct(WRITE, &zv->zv_disk->part0, start_jif); BIO_END_IO(bio, -error); kmem_free(zvr, sizeof (zv_request_t)); } static void zvol_read(void *arg) { zv_request_t *zvr = arg; struct bio *bio = zvr->bio; uio_t uio; zvol_state_t *zv = zvr->zv; uint64_t volsize = zv->zv_volsize; int error = 0; unsigned long start_jif; uio_from_bio(&uio, bio); ASSERT(zv && zv->zv_open_count > 0); start_jif = jiffies; generic_start_io_acct(READ, bio_sectors(bio), &zv->zv_disk->part0); while (uio.uio_resid > 0 && uio.uio_loffset < volsize) { uint64_t bytes = MIN(uio.uio_resid, DMU_MAX_ACCESS >> 1); /* don't read past the end */ if (bytes > volsize - uio.uio_loffset) bytes = volsize - uio.uio_loffset; error = dmu_read_uio_dnode(zv->zv_dn, &uio, bytes); if (error) { /* convert checksum errors into IO errors */ if (error == ECKSUM) error = SET_ERROR(EIO); break; } } zfs_range_unlock(zvr->rl); rw_exit(&zv->zv_suspend_lock); generic_end_io_acct(READ, &zv->zv_disk->part0, start_jif); BIO_END_IO(bio, -error); kmem_free(zvr, sizeof (zv_request_t)); } static MAKE_REQUEST_FN_RET zvol_request(struct request_queue *q, struct bio *bio) { zvol_state_t *zv = q->queuedata; fstrans_cookie_t cookie = spl_fstrans_mark(); uint64_t offset = BIO_BI_SECTOR(bio) << 9; uint64_t size = BIO_BI_SIZE(bio); int rw = bio_data_dir(bio); zv_request_t *zvr; if (bio_has_data(bio) && offset + size > zv->zv_volsize) { printk(KERN_INFO "%s: bad access: offset=%llu, size=%lu\n", zv->zv_disk->disk_name, (long long unsigned)offset, (long unsigned)size); BIO_END_IO(bio, -SET_ERROR(EIO)); goto out; } if (rw == WRITE) { if (unlikely(zv->zv_flags & ZVOL_RDONLY)) { BIO_END_IO(bio, -SET_ERROR(EROFS)); goto out; } /* * To be released in the I/O function. See the comment on * zfs_range_lock below. */ rw_enter(&zv->zv_suspend_lock, RW_READER); /* bio marked as FLUSH need to flush before write */ if (bio_is_flush(bio)) zil_commit(zv->zv_zilog, ZVOL_OBJ); /* Some requests are just for flush and nothing else. */ if (size == 0) { rw_exit(&zv->zv_suspend_lock); BIO_END_IO(bio, 0); goto out; } zvr = kmem_alloc(sizeof (zv_request_t), KM_SLEEP); zvr->zv = zv; zvr->bio = bio; /* * To be released in the I/O function. Since the I/O functions * are asynchronous, we take it here synchronously to make * sure overlapped I/Os are properly ordered. */ zvr->rl = zfs_range_lock(&zv->zv_range_lock, offset, size, RL_WRITER); if (bio_is_discard(bio) || bio_is_secure_erase(bio)) { if (zvol_request_sync || taskq_dispatch(zvol_taskq, zvol_discard, zvr, TQ_SLEEP) == TASKQID_INVALID) zvol_discard(zvr); } else { if (zvol_request_sync || taskq_dispatch(zvol_taskq, zvol_write, zvr, TQ_SLEEP) == TASKQID_INVALID) zvol_write(zvr); } } else { zvr = kmem_alloc(sizeof (zv_request_t), KM_SLEEP); zvr->zv = zv; zvr->bio = bio; rw_enter(&zv->zv_suspend_lock, RW_READER); zvr->rl = zfs_range_lock(&zv->zv_range_lock, offset, size, RL_READER); if (zvol_request_sync || taskq_dispatch(zvol_taskq, zvol_read, zvr, TQ_SLEEP) == TASKQID_INVALID) zvol_read(zvr); } out: spl_fstrans_unmark(cookie); #ifdef HAVE_MAKE_REQUEST_FN_RET_INT return (0); #elif defined(HAVE_MAKE_REQUEST_FN_RET_QC) return (BLK_QC_T_NONE); #endif } static void zvol_get_done(zgd_t *zgd, int error) { if (zgd->zgd_db) dmu_buf_rele(zgd->zgd_db, zgd); zfs_range_unlock(zgd->zgd_rl); if (error == 0 && zgd->zgd_bp) zil_add_block(zgd->zgd_zilog, zgd->zgd_bp); kmem_free(zgd, sizeof (zgd_t)); } /* * Get data to generate a TX_WRITE intent log record. */ static int zvol_get_data(void *arg, lr_write_t *lr, char *buf, zio_t *zio) { zvol_state_t *zv = arg; uint64_t offset = lr->lr_offset; uint64_t size = lr->lr_length; dmu_buf_t *db; zgd_t *zgd; int error; ASSERT(zio != NULL); ASSERT(size != 0); zgd = (zgd_t *)kmem_zalloc(sizeof (zgd_t), KM_SLEEP); zgd->zgd_zilog = zv->zv_zilog; zgd->zgd_rl = zfs_range_lock(&zv->zv_range_lock, offset, size, RL_READER); /* * Write records come in two flavors: immediate and indirect. * For small writes it's cheaper to store the data with the * log record (immediate); for large writes it's cheaper to * sync the data and get a pointer to it (indirect) so that * we don't have to write the data twice. */ if (buf != NULL) { /* immediate write */ error = dmu_read_by_dnode(zv->zv_dn, offset, size, buf, DMU_READ_NO_PREFETCH); } else { size = zv->zv_volblocksize; offset = P2ALIGN_TYPED(offset, size, uint64_t); error = dmu_buf_hold_by_dnode(zv->zv_dn, offset, zgd, &db, DMU_READ_NO_PREFETCH); if (error == 0) { blkptr_t *bp = &lr->lr_blkptr; zgd->zgd_db = db; zgd->zgd_bp = bp; ASSERT(db != NULL); ASSERT(db->db_offset == offset); ASSERT(db->db_size == size); error = dmu_sync(zio, lr->lr_common.lrc_txg, zvol_get_done, zgd); if (error == 0) return (0); } } zvol_get_done(zgd, error); return (SET_ERROR(error)); } /* * The zvol_state_t's are inserted into zvol_state_list and zvol_htable. */ static void zvol_insert(zvol_state_t *zv) { ASSERT(MUTEX_HELD(&zvol_state_lock)); ASSERT3U(MINOR(zv->zv_dev) & ZVOL_MINOR_MASK, ==, 0); list_insert_head(&zvol_state_list, zv); hlist_add_head(&zv->zv_hlink, ZVOL_HT_HEAD(zv->zv_hash)); } /* * Simply remove the zvol from to list of zvols. */ static void zvol_remove(zvol_state_t *zv) { ASSERT(MUTEX_HELD(&zvol_state_lock)); list_remove(&zvol_state_list, zv); hlist_del(&zv->zv_hlink); } /* * Setup zv after we just own the zv->objset */ static int zvol_setup_zv(zvol_state_t *zv) { uint64_t volsize; int error; uint64_t ro; objset_t *os = zv->zv_objset; ASSERT(MUTEX_HELD(&zv->zv_state_lock) && RW_LOCK_HELD(&zv->zv_suspend_lock)); error = dsl_prop_get_integer(zv->zv_name, "readonly", &ro, NULL); if (error) return (SET_ERROR(error)); error = zap_lookup(os, ZVOL_ZAP_OBJ, "size", 8, 1, &volsize); if (error) return (SET_ERROR(error)); error = dnode_hold(os, ZVOL_OBJ, FTAG, &zv->zv_dn); if (error) return (SET_ERROR(error)); set_capacity(zv->zv_disk, volsize >> 9); zv->zv_volsize = volsize; zv->zv_zilog = zil_open(os, zvol_get_data); if (ro || dmu_objset_is_snapshot(os) || !spa_writeable(dmu_objset_spa(os))) { set_disk_ro(zv->zv_disk, 1); zv->zv_flags |= ZVOL_RDONLY; } else { set_disk_ro(zv->zv_disk, 0); zv->zv_flags &= ~ZVOL_RDONLY; } return (0); } /* * Shutdown every zv_objset related stuff except zv_objset itself. * The is the reverse of zvol_setup_zv. */ static void zvol_shutdown_zv(zvol_state_t *zv) { ASSERT(MUTEX_HELD(&zv->zv_state_lock) && RW_LOCK_HELD(&zv->zv_suspend_lock)); zil_close(zv->zv_zilog); zv->zv_zilog = NULL; dnode_rele(zv->zv_dn, FTAG); zv->zv_dn = NULL; /* * Evict cached data */ if (dsl_dataset_is_dirty(dmu_objset_ds(zv->zv_objset)) && !(zv->zv_flags & ZVOL_RDONLY)) txg_wait_synced(dmu_objset_pool(zv->zv_objset), 0); (void) dmu_objset_evict_dbufs(zv->zv_objset); } /* * return the proper tag for rollback and recv */ void * zvol_tag(zvol_state_t *zv) { ASSERT(RW_WRITE_HELD(&zv->zv_suspend_lock)); return (zv->zv_open_count > 0 ? zv : NULL); } /* * Suspend the zvol for recv and rollback. */ zvol_state_t * zvol_suspend(const char *name) { zvol_state_t *zv; zv = zvol_find_by_name(name, RW_WRITER); if (zv == NULL) return (NULL); /* block all I/O, release in zvol_resume. */ ASSERT(MUTEX_HELD(&zv->zv_state_lock) && RW_WRITE_HELD(&zv->zv_suspend_lock)); atomic_inc(&zv->zv_suspend_ref); if (zv->zv_open_count > 0) zvol_shutdown_zv(zv); /* * do not hold zv_state_lock across suspend/resume to * avoid locking up zvol lookups */ mutex_exit(&zv->zv_state_lock); /* zv_suspend_lock is released in zvol_resume() */ return (zv); } int zvol_resume(zvol_state_t *zv) { int error = 0; ASSERT(RW_WRITE_HELD(&zv->zv_suspend_lock)); mutex_enter(&zv->zv_state_lock); if (zv->zv_open_count > 0) { VERIFY0(dmu_objset_hold(zv->zv_name, zv, &zv->zv_objset)); VERIFY3P(zv->zv_objset->os_dsl_dataset->ds_owner, ==, zv); VERIFY(dsl_dataset_long_held(zv->zv_objset->os_dsl_dataset)); dmu_objset_rele(zv->zv_objset, zv); error = zvol_setup_zv(zv); } mutex_exit(&zv->zv_state_lock); rw_exit(&zv->zv_suspend_lock); /* * We need this because we don't hold zvol_state_lock while releasing * zv_suspend_lock. zvol_remove_minors_impl thus cannot check * zv_suspend_lock to determine it is safe to free because rwlock is * not inherent atomic. */ atomic_dec(&zv->zv_suspend_ref); return (SET_ERROR(error)); } static int zvol_first_open(zvol_state_t *zv) { objset_t *os; int error, locked = 0; ASSERT(RW_READ_HELD(&zv->zv_suspend_lock)); ASSERT(MUTEX_HELD(&zv->zv_state_lock)); /* * In all other cases the spa_namespace_lock is taken before the * bdev->bd_mutex lock. But in this case the Linux __blkdev_get() * function calls fops->open() with the bdev->bd_mutex lock held. * This deadlock can be easily observed with zvols used as vdevs. * * To avoid a potential lock inversion deadlock we preemptively * try to take the spa_namespace_lock(). Normally it will not * be contended and this is safe because spa_open_common() handles * the case where the caller already holds the spa_namespace_lock. * * When it is contended we risk a lock inversion if we were to * block waiting for the lock. Luckily, the __blkdev_get() * function allows us to return -ERESTARTSYS which will result in * bdev->bd_mutex being dropped, reacquired, and fops->open() being * called again. This process can be repeated safely until both * locks are acquired. */ if (!mutex_owned(&spa_namespace_lock)) { locked = mutex_tryenter(&spa_namespace_lock); if (!locked) return (-SET_ERROR(ERESTARTSYS)); } /* lie and say we're read-only */ error = dmu_objset_own(zv->zv_name, DMU_OST_ZVOL, 1, zv, &os); if (error) goto out_mutex; zv->zv_objset = os; error = zvol_setup_zv(zv); if (error) { dmu_objset_disown(os, zv); zv->zv_objset = NULL; } out_mutex: if (locked) mutex_exit(&spa_namespace_lock); return (SET_ERROR(-error)); } static void zvol_last_close(zvol_state_t *zv) { ASSERT(RW_READ_HELD(&zv->zv_suspend_lock)); ASSERT(MUTEX_HELD(&zv->zv_state_lock)); zvol_shutdown_zv(zv); dmu_objset_disown(zv->zv_objset, zv); zv->zv_objset = NULL; } static int zvol_open(struct block_device *bdev, fmode_t flag) { zvol_state_t *zv; int error = 0; boolean_t drop_suspend = B_FALSE; ASSERT(!mutex_owned(&zvol_state_lock)); mutex_enter(&zvol_state_lock); /* * Obtain a copy of private_data under the zvol_state_lock to make * sure that either the result of zvol free code path setting * bdev->bd_disk->private_data to NULL is observed, or zvol_free() * is not called on this zv because of the positive zv_open_count. */ zv = bdev->bd_disk->private_data; if (zv == NULL) { mutex_exit(&zvol_state_lock); return (SET_ERROR(-ENXIO)); } /* take zv_suspend_lock before zv_state_lock */ rw_enter(&zv->zv_suspend_lock, RW_READER); mutex_enter(&zv->zv_state_lock); /* * make sure zvol is not suspended during first open * (hold zv_suspend_lock), otherwise, drop the lock */ if (zv->zv_open_count == 0) { drop_suspend = B_TRUE; } else { rw_exit(&zv->zv_suspend_lock); } mutex_exit(&zvol_state_lock); if (zv->zv_open_count == 0) { error = zvol_first_open(zv); if (error) goto out_mutex; } if ((flag & FMODE_WRITE) && (zv->zv_flags & ZVOL_RDONLY)) { error = -EROFS; goto out_open_count; } zv->zv_open_count++; check_disk_change(bdev); out_open_count: if (zv->zv_open_count == 0) zvol_last_close(zv); out_mutex: mutex_exit(&zv->zv_state_lock); if (drop_suspend) rw_exit(&zv->zv_suspend_lock); return (SET_ERROR(error)); } #ifdef HAVE_BLOCK_DEVICE_OPERATIONS_RELEASE_VOID static void #else static int #endif zvol_release(struct gendisk *disk, fmode_t mode) { zvol_state_t *zv; boolean_t drop_suspend = B_FALSE; ASSERT(!mutex_owned(&zvol_state_lock)); mutex_enter(&zvol_state_lock); zv = disk->private_data; ASSERT(zv && zv->zv_open_count > 0); /* take zv_suspend_lock before zv_state_lock */ rw_enter(&zv->zv_suspend_lock, RW_READER); mutex_enter(&zv->zv_state_lock); mutex_exit(&zvol_state_lock); /* * make sure zvol is not suspended during last close * (hold zv_suspend_lock), otherwise, drop the lock */ if (zv->zv_open_count == 1) drop_suspend = B_TRUE; else rw_exit(&zv->zv_suspend_lock); zv->zv_open_count--; if (zv->zv_open_count == 0) zvol_last_close(zv); mutex_exit(&zv->zv_state_lock); if (drop_suspend) rw_exit(&zv->zv_suspend_lock); #ifndef HAVE_BLOCK_DEVICE_OPERATIONS_RELEASE_VOID return (0); #endif } static int zvol_ioctl(struct block_device *bdev, fmode_t mode, unsigned int cmd, unsigned long arg) { zvol_state_t *zv = bdev->bd_disk->private_data; int error = 0; ASSERT(zv && zv->zv_open_count > 0); switch (cmd) { case BLKFLSBUF: fsync_bdev(bdev); invalidate_bdev(bdev); rw_enter(&zv->zv_suspend_lock, RW_READER); if (dsl_dataset_is_dirty(dmu_objset_ds(zv->zv_objset)) && !(zv->zv_flags & ZVOL_RDONLY)) txg_wait_synced(dmu_objset_pool(zv->zv_objset), 0); rw_exit(&zv->zv_suspend_lock); break; case BLKZNAME: mutex_enter(&zv->zv_state_lock); error = copy_to_user((void *)arg, zv->zv_name, MAXNAMELEN); mutex_exit(&zv->zv_state_lock); break; default: error = -ENOTTY; break; } return (SET_ERROR(error)); } #ifdef CONFIG_COMPAT static int zvol_compat_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd, unsigned long arg) { return (zvol_ioctl(bdev, mode, cmd, arg)); } #else #define zvol_compat_ioctl NULL #endif static int zvol_media_changed(struct gendisk *disk) { zvol_state_t *zv = disk->private_data; ASSERT(zv && zv->zv_open_count > 0); return (zv->zv_changed); } static int zvol_revalidate_disk(struct gendisk *disk) { zvol_state_t *zv = disk->private_data; ASSERT(zv && zv->zv_open_count > 0); zv->zv_changed = 0; set_capacity(zv->zv_disk, zv->zv_volsize >> 9); return (0); } /* * Provide a simple virtual geometry for legacy compatibility. For devices * smaller than 1 MiB a small head and sector count is used to allow very * tiny devices. For devices over 1 Mib a standard head and sector count * is used to keep the cylinders count reasonable. */ static int zvol_getgeo(struct block_device *bdev, struct hd_geometry *geo) { zvol_state_t *zv = bdev->bd_disk->private_data; sector_t sectors; ASSERT(zv && zv->zv_open_count > 0); sectors = get_capacity(zv->zv_disk); if (sectors > 2048) { geo->heads = 16; geo->sectors = 63; } else { geo->heads = 2; geo->sectors = 4; } geo->start = 0; geo->cylinders = sectors / (geo->heads * geo->sectors); return (0); } static struct kobject * zvol_probe(dev_t dev, int *part, void *arg) { zvol_state_t *zv; struct kobject *kobj; zv = zvol_find_by_dev(dev); kobj = zv ? get_disk(zv->zv_disk) : NULL; ASSERT(zv == NULL || MUTEX_HELD(&zv->zv_state_lock)); if (zv) mutex_exit(&zv->zv_state_lock); return (kobj); } #ifdef HAVE_BDEV_BLOCK_DEVICE_OPERATIONS static struct block_device_operations zvol_ops = { .open = zvol_open, .release = zvol_release, .ioctl = zvol_ioctl, .compat_ioctl = zvol_compat_ioctl, .media_changed = zvol_media_changed, .revalidate_disk = zvol_revalidate_disk, .getgeo = zvol_getgeo, .owner = THIS_MODULE, }; #else /* HAVE_BDEV_BLOCK_DEVICE_OPERATIONS */ static int zvol_open_by_inode(struct inode *inode, struct file *file) { return (zvol_open(inode->i_bdev, file->f_mode)); } static int zvol_release_by_inode(struct inode *inode, struct file *file) { return (zvol_release(inode->i_bdev->bd_disk, file->f_mode)); } static int zvol_ioctl_by_inode(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg) { if (file == NULL || inode == NULL) return (SET_ERROR(-EINVAL)); return (zvol_ioctl(inode->i_bdev, file->f_mode, cmd, arg)); } #ifdef CONFIG_COMPAT static long zvol_compat_ioctl_by_inode(struct file *file, unsigned int cmd, unsigned long arg) { if (file == NULL) return (SET_ERROR(-EINVAL)); return (zvol_compat_ioctl(file->f_dentry->d_inode->i_bdev, file->f_mode, cmd, arg)); } #else #define zvol_compat_ioctl_by_inode NULL #endif static struct block_device_operations zvol_ops = { .open = zvol_open_by_inode, .release = zvol_release_by_inode, .ioctl = zvol_ioctl_by_inode, .compat_ioctl = zvol_compat_ioctl_by_inode, .media_changed = zvol_media_changed, .revalidate_disk = zvol_revalidate_disk, .getgeo = zvol_getgeo, .owner = THIS_MODULE, }; #endif /* HAVE_BDEV_BLOCK_DEVICE_OPERATIONS */ /* * Allocate memory for a new zvol_state_t and setup the required * request queue and generic disk structures for the block device. */ static zvol_state_t * zvol_alloc(dev_t dev, const char *name) { zvol_state_t *zv; zv = kmem_zalloc(sizeof (zvol_state_t), KM_SLEEP); list_link_init(&zv->zv_next); mutex_init(&zv->zv_state_lock, NULL, MUTEX_DEFAULT, NULL); zv->zv_queue = blk_alloc_queue(GFP_ATOMIC); if (zv->zv_queue == NULL) goto out_kmem; blk_queue_make_request(zv->zv_queue, zvol_request); blk_queue_set_write_cache(zv->zv_queue, B_TRUE, B_TRUE); /* Limit read-ahead to a single page to prevent over-prefetching. */ blk_queue_set_read_ahead(zv->zv_queue, 1); /* Disable write merging in favor of the ZIO pipeline. */ queue_flag_set_unlocked(QUEUE_FLAG_NOMERGES, zv->zv_queue); zv->zv_disk = alloc_disk(ZVOL_MINORS); if (zv->zv_disk == NULL) goto out_queue; zv->zv_queue->queuedata = zv; zv->zv_dev = dev; zv->zv_open_count = 0; strlcpy(zv->zv_name, name, MAXNAMELEN); zfs_rlock_init(&zv->zv_range_lock); rw_init(&zv->zv_suspend_lock, NULL, RW_DEFAULT, NULL); zv->zv_disk->major = zvol_major; zv->zv_disk->first_minor = (dev & MINORMASK); zv->zv_disk->fops = &zvol_ops; zv->zv_disk->private_data = zv; zv->zv_disk->queue = zv->zv_queue; snprintf(zv->zv_disk->disk_name, DISK_NAME_LEN, "%s%d", ZVOL_DEV_NAME, (dev & MINORMASK)); return (zv); out_queue: blk_cleanup_queue(zv->zv_queue); out_kmem: kmem_free(zv, sizeof (zvol_state_t)); return (NULL); } /* * Cleanup then free a zvol_state_t which was created by zvol_alloc(). * At this time, the structure is not opened by anyone, is taken off * the zvol_state_list, and has its private data set to NULL. * The zvol_state_lock is dropped. */ static void zvol_free(void *arg) { zvol_state_t *zv = arg; ASSERT(!MUTEX_HELD(&zvol_state_lock)); ASSERT(!RW_LOCK_HELD(&zv->zv_suspend_lock)); ASSERT(!MUTEX_HELD(&zv->zv_state_lock)); ASSERT(zv->zv_open_count == 0); ASSERT(zv->zv_disk->private_data == NULL); rw_destroy(&zv->zv_suspend_lock); zfs_rlock_destroy(&zv->zv_range_lock); del_gendisk(zv->zv_disk); blk_cleanup_queue(zv->zv_queue); put_disk(zv->zv_disk); ida_simple_remove(&zvol_ida, MINOR(zv->zv_dev) >> ZVOL_MINOR_BITS); mutex_destroy(&zv->zv_state_lock); kmem_free(zv, sizeof (zvol_state_t)); } /* * Create a block device minor node and setup the linkage between it * and the specified volume. Once this function returns the block * device is live and ready for use. */ static int zvol_create_minor_impl(const char *name) { zvol_state_t *zv; objset_t *os; dmu_object_info_t *doi; uint64_t volsize; uint64_t len; unsigned minor = 0; int error = 0; int idx; uint64_t hash = zvol_name_hash(name); idx = ida_simple_get(&zvol_ida, 0, 0, kmem_flags_convert(KM_SLEEP)); if (idx < 0) return (SET_ERROR(-idx)); minor = idx << ZVOL_MINOR_BITS; zv = zvol_find_by_name_hash(name, hash, RW_NONE); if (zv) { ASSERT(MUTEX_HELD(&zv->zv_state_lock)); mutex_exit(&zv->zv_state_lock); ida_simple_remove(&zvol_ida, idx); return (SET_ERROR(EEXIST)); } doi = kmem_alloc(sizeof (dmu_object_info_t), KM_SLEEP); error = dmu_objset_own(name, DMU_OST_ZVOL, B_TRUE, FTAG, &os); if (error) goto out_doi; error = dmu_object_info(os, ZVOL_OBJ, doi); if (error) goto out_dmu_objset_disown; error = zap_lookup(os, ZVOL_ZAP_OBJ, "size", 8, 1, &volsize); if (error) goto out_dmu_objset_disown; zv = zvol_alloc(MKDEV(zvol_major, minor), name); if (zv == NULL) { error = SET_ERROR(EAGAIN); goto out_dmu_objset_disown; } zv->zv_hash = hash; if (dmu_objset_is_snapshot(os)) zv->zv_flags |= ZVOL_RDONLY; zv->zv_volblocksize = doi->doi_data_block_size; zv->zv_volsize = volsize; zv->zv_objset = os; set_capacity(zv->zv_disk, zv->zv_volsize >> 9); blk_queue_max_hw_sectors(zv->zv_queue, (DMU_MAX_ACCESS / 4) >> 9); blk_queue_max_segments(zv->zv_queue, UINT16_MAX); blk_queue_max_segment_size(zv->zv_queue, UINT_MAX); blk_queue_physical_block_size(zv->zv_queue, zv->zv_volblocksize); blk_queue_io_opt(zv->zv_queue, zv->zv_volblocksize); blk_queue_max_discard_sectors(zv->zv_queue, (zvol_max_discard_blocks * zv->zv_volblocksize) >> 9); blk_queue_discard_granularity(zv->zv_queue, zv->zv_volblocksize); queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, zv->zv_queue); #ifdef QUEUE_FLAG_NONROT queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zv->zv_queue); #endif #ifdef QUEUE_FLAG_ADD_RANDOM queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, zv->zv_queue); #endif if (spa_writeable(dmu_objset_spa(os))) { if (zil_replay_disable) zil_destroy(dmu_objset_zil(os), B_FALSE); else zil_replay(os, zv, zvol_replay_vector); } /* * When udev detects the addition of the device it will immediately * invoke blkid(8) to determine the type of content on the device. * Prefetching the blocks commonly scanned by blkid(8) will speed * up this process. */ len = MIN(MAX(zvol_prefetch_bytes, 0), SPA_MAXBLOCKSIZE); if (len > 0) { dmu_prefetch(os, ZVOL_OBJ, 0, 0, len, ZIO_PRIORITY_SYNC_READ); dmu_prefetch(os, ZVOL_OBJ, 0, volsize - len, len, ZIO_PRIORITY_SYNC_READ); } zv->zv_objset = NULL; out_dmu_objset_disown: dmu_objset_disown(os, FTAG); out_doi: kmem_free(doi, sizeof (dmu_object_info_t)); if (error == 0) { mutex_enter(&zvol_state_lock); zvol_insert(zv); mutex_exit(&zvol_state_lock); add_disk(zv->zv_disk); } else { ida_simple_remove(&zvol_ida, idx); } return (SET_ERROR(error)); } /* * Rename a block device minor mode for the specified volume. */ static void zvol_rename_minor(zvol_state_t *zv, const char *newname) { int readonly = get_disk_ro(zv->zv_disk); ASSERT(MUTEX_HELD(&zvol_state_lock)); ASSERT(MUTEX_HELD(&zv->zv_state_lock)); strlcpy(zv->zv_name, newname, sizeof (zv->zv_name)); /* move to new hashtable entry */ zv->zv_hash = zvol_name_hash(zv->zv_name); hlist_del(&zv->zv_hlink); hlist_add_head(&zv->zv_hlink, ZVOL_HT_HEAD(zv->zv_hash)); /* * The block device's read-only state is briefly changed causing * a KOBJ_CHANGE uevent to be issued. This ensures udev detects * the name change and fixes the symlinks. This does not change * ZVOL_RDONLY in zv->zv_flags so the actual read-only state never * changes. This would normally be done using kobject_uevent() but * that is a GPL-only symbol which is why we need this workaround. */ set_disk_ro(zv->zv_disk, !readonly); set_disk_ro(zv->zv_disk, readonly); } typedef struct minors_job { list_t *list; list_node_t link; /* input */ char *name; /* output */ int error; } minors_job_t; /* * Prefetch zvol dnodes for the minors_job */ static void zvol_prefetch_minors_impl(void *arg) { minors_job_t *job = arg; char *dsname = job->name; objset_t *os = NULL; job->error = dmu_objset_own(dsname, DMU_OST_ZVOL, B_TRUE, FTAG, &os); if (job->error == 0) { dmu_prefetch(os, ZVOL_OBJ, 0, 0, 0, ZIO_PRIORITY_SYNC_READ); dmu_objset_disown(os, FTAG); } } /* * Mask errors to continue dmu_objset_find() traversal */ static int zvol_create_snap_minor_cb(const char *dsname, void *arg) { minors_job_t *j = arg; list_t *minors_list = j->list; const char *name = j->name; ASSERT0(MUTEX_HELD(&spa_namespace_lock)); /* skip the designated dataset */ if (name && strcmp(dsname, name) == 0) return (0); /* at this point, the dsname should name a snapshot */ if (strchr(dsname, '@') == 0) { dprintf("zvol_create_snap_minor_cb(): " "%s is not a shapshot name\n", dsname); } else { minors_job_t *job; char *n = strdup(dsname); if (n == NULL) return (0); job = kmem_alloc(sizeof (minors_job_t), KM_SLEEP); job->name = n; job->list = minors_list; job->error = 0; list_insert_tail(minors_list, job); /* don't care if dispatch fails, because job->error is 0 */ taskq_dispatch(system_taskq, zvol_prefetch_minors_impl, job, TQ_SLEEP); } return (0); } /* * Mask errors to continue dmu_objset_find() traversal */ static int zvol_create_minors_cb(const char *dsname, void *arg) { uint64_t snapdev; int error; list_t *minors_list = arg; ASSERT0(MUTEX_HELD(&spa_namespace_lock)); error = dsl_prop_get_integer(dsname, "snapdev", &snapdev, NULL); if (error) return (0); /* * Given the name and the 'snapdev' property, create device minor nodes * with the linkages to zvols/snapshots as needed. * If the name represents a zvol, create a minor node for the zvol, then * check if its snapshots are 'visible', and if so, iterate over the * snapshots and create device minor nodes for those. */ if (strchr(dsname, '@') == 0) { minors_job_t *job; char *n = strdup(dsname); if (n == NULL) return (0); job = kmem_alloc(sizeof (minors_job_t), KM_SLEEP); job->name = n; job->list = minors_list; job->error = 0; list_insert_tail(minors_list, job); /* don't care if dispatch fails, because job->error is 0 */ taskq_dispatch(system_taskq, zvol_prefetch_minors_impl, job, TQ_SLEEP); if (snapdev == ZFS_SNAPDEV_VISIBLE) { /* * traverse snapshots only, do not traverse children, * and skip the 'dsname' */ error = dmu_objset_find((char *)dsname, zvol_create_snap_minor_cb, (void *)job, DS_FIND_SNAPSHOTS); } } else { dprintf("zvol_create_minors_cb(): %s is not a zvol name\n", dsname); } return (0); } /* * Create minors for the specified dataset, including children and snapshots. * Pay attention to the 'snapdev' property and iterate over the snapshots * only if they are 'visible'. This approach allows one to assure that the * snapshot metadata is read from disk only if it is needed. * * The name can represent a dataset to be recursively scanned for zvols and * their snapshots, or a single zvol snapshot. If the name represents a * dataset, the scan is performed in two nested stages: * - scan the dataset for zvols, and * - for each zvol, create a minor node, then check if the zvol's snapshots * are 'visible', and only then iterate over the snapshots if needed * * If the name represents a snapshot, a check is performed if the snapshot is * 'visible' (which also verifies that the parent is a zvol), and if so, * a minor node for that snapshot is created. */ static int zvol_create_minors_impl(const char *name) { int error = 0; fstrans_cookie_t cookie; char *atp, *parent; list_t minors_list; minors_job_t *job; if (zvol_inhibit_dev) return (0); /* * This is the list for prefetch jobs. Whenever we found a match * during dmu_objset_find, we insert a minors_job to the list and do * taskq_dispatch to parallel prefetch zvol dnodes. Note we don't need * any lock because all list operation is done on the current thread. * * We will use this list to do zvol_create_minor_impl after prefetch * so we don't have to traverse using dmu_objset_find again. */ list_create(&minors_list, sizeof (minors_job_t), offsetof(minors_job_t, link)); parent = kmem_alloc(MAXPATHLEN, KM_SLEEP); (void) strlcpy(parent, name, MAXPATHLEN); if ((atp = strrchr(parent, '@')) != NULL) { uint64_t snapdev; *atp = '\0'; error = dsl_prop_get_integer(parent, "snapdev", &snapdev, NULL); if (error == 0 && snapdev == ZFS_SNAPDEV_VISIBLE) error = zvol_create_minor_impl(name); } else { cookie = spl_fstrans_mark(); error = dmu_objset_find(parent, zvol_create_minors_cb, &minors_list, DS_FIND_CHILDREN); spl_fstrans_unmark(cookie); } kmem_free(parent, MAXPATHLEN); taskq_wait_outstanding(system_taskq, 0); /* * Prefetch is completed, we can do zvol_create_minor_impl * sequentially. */ while ((job = list_head(&minors_list)) != NULL) { list_remove(&minors_list, job); if (!job->error) zvol_create_minor_impl(job->name); strfree(job->name); kmem_free(job, sizeof (minors_job_t)); } list_destroy(&minors_list); return (SET_ERROR(error)); } /* * Remove minors for specified dataset including children and snapshots. */ static void zvol_remove_minors_impl(const char *name) { zvol_state_t *zv, *zv_next; int namelen = ((name) ? strlen(name) : 0); taskqid_t t, tid = TASKQID_INVALID; list_t free_list; if (zvol_inhibit_dev) return; list_create(&free_list, sizeof (zvol_state_t), offsetof(zvol_state_t, zv_next)); mutex_enter(&zvol_state_lock); for (zv = list_head(&zvol_state_list); zv != NULL; zv = zv_next) { zv_next = list_next(&zvol_state_list, zv); mutex_enter(&zv->zv_state_lock); if (name == NULL || strcmp(zv->zv_name, name) == 0 || (strncmp(zv->zv_name, name, namelen) == 0 && (zv->zv_name[namelen] == '/' || zv->zv_name[namelen] == '@'))) { /* * By holding zv_state_lock here, we guarantee that no * one is currently using this zv */ /* If in use, leave alone */ if (zv->zv_open_count > 0 || atomic_read(&zv->zv_suspend_ref)) { mutex_exit(&zv->zv_state_lock); continue; } zvol_remove(zv); /* * clear this while holding zvol_state_lock so * zvol_open won't open it */ zv->zv_disk->private_data = NULL; /* Drop zv_state_lock before zvol_free() */ mutex_exit(&zv->zv_state_lock); /* try parallel zv_free, if failed do it in place */ t = taskq_dispatch(system_taskq, zvol_free, zv, TQ_SLEEP); if (t == TASKQID_INVALID) list_insert_head(&free_list, zv); else tid = t; } else { mutex_exit(&zv->zv_state_lock); } } mutex_exit(&zvol_state_lock); /* * Drop zvol_state_lock before calling zvol_free() */ while ((zv = list_head(&free_list)) != NULL) { list_remove(&free_list, zv); zvol_free(zv); } if (tid != TASKQID_INVALID) taskq_wait_outstanding(system_taskq, tid); } /* Remove minor for this specific snapshot only */ static void zvol_remove_minor_impl(const char *name) { zvol_state_t *zv = NULL, *zv_next; if (zvol_inhibit_dev) return; if (strchr(name, '@') == NULL) return; mutex_enter(&zvol_state_lock); for (zv = list_head(&zvol_state_list); zv != NULL; zv = zv_next) { zv_next = list_next(&zvol_state_list, zv); mutex_enter(&zv->zv_state_lock); if (strcmp(zv->zv_name, name) == 0) { /* * By holding zv_state_lock here, we guarantee that no * one is currently using this zv */ /* If in use, leave alone */ if (zv->zv_open_count > 0 || atomic_read(&zv->zv_suspend_ref)) { mutex_exit(&zv->zv_state_lock); continue; } zvol_remove(zv); /* clear this so zvol_open won't open it */ zv->zv_disk->private_data = NULL; mutex_exit(&zv->zv_state_lock); break; } else { mutex_exit(&zv->zv_state_lock); } } /* Drop zvol_state_lock before calling zvol_free() */ mutex_exit(&zvol_state_lock); if (zv != NULL) zvol_free(zv); } /* * Rename minors for specified dataset including children and snapshots. */ static void zvol_rename_minors_impl(const char *oldname, const char *newname) { zvol_state_t *zv, *zv_next; int oldnamelen, newnamelen; if (zvol_inhibit_dev) return; oldnamelen = strlen(oldname); newnamelen = strlen(newname); mutex_enter(&zvol_state_lock); for (zv = list_head(&zvol_state_list); zv != NULL; zv = zv_next) { zv_next = list_next(&zvol_state_list, zv); mutex_enter(&zv->zv_state_lock); /* If in use, leave alone */ if (zv->zv_open_count > 0) { mutex_exit(&zv->zv_state_lock); continue; } if (strcmp(zv->zv_name, oldname) == 0) { zvol_rename_minor(zv, newname); } else if (strncmp(zv->zv_name, oldname, oldnamelen) == 0 && (zv->zv_name[oldnamelen] == '/' || zv->zv_name[oldnamelen] == '@')) { char *name = kmem_asprintf("%s%c%s", newname, zv->zv_name[oldnamelen], zv->zv_name + oldnamelen + 1); zvol_rename_minor(zv, name); kmem_free(name, strlen(name + 1)); } mutex_exit(&zv->zv_state_lock); } mutex_exit(&zvol_state_lock); } typedef struct zvol_snapdev_cb_arg { uint64_t snapdev; } zvol_snapdev_cb_arg_t; static int zvol_set_snapdev_cb(const char *dsname, void *param) { zvol_snapdev_cb_arg_t *arg = param; if (strchr(dsname, '@') == NULL) return (0); switch (arg->snapdev) { case ZFS_SNAPDEV_VISIBLE: (void) zvol_create_minor_impl(dsname); break; case ZFS_SNAPDEV_HIDDEN: (void) zvol_remove_minor_impl(dsname); break; } return (0); } static void zvol_set_snapdev_impl(char *name, uint64_t snapdev) { zvol_snapdev_cb_arg_t arg = {snapdev}; fstrans_cookie_t cookie = spl_fstrans_mark(); /* * The zvol_set_snapdev_sync() sets snapdev appropriately * in the dataset hierarchy. Here, we only scan snapshots. */ dmu_objset_find(name, zvol_set_snapdev_cb, &arg, DS_FIND_SNAPSHOTS); spl_fstrans_unmark(cookie); } static zvol_task_t * zvol_task_alloc(zvol_async_op_t op, const char *name1, const char *name2, uint64_t snapdev) { zvol_task_t *task; char *delim; /* Never allow tasks on hidden names. */ if (name1[0] == '$') return (NULL); task = kmem_zalloc(sizeof (zvol_task_t), KM_SLEEP); task->op = op; task->snapdev = snapdev; delim = strchr(name1, '/'); strlcpy(task->pool, name1, delim ? (delim - name1 + 1) : MAXNAMELEN); strlcpy(task->name1, name1, MAXNAMELEN); if (name2 != NULL) strlcpy(task->name2, name2, MAXNAMELEN); return (task); } static void zvol_task_free(zvol_task_t *task) { kmem_free(task, sizeof (zvol_task_t)); } /* * The worker thread function performed asynchronously. */ static void zvol_task_cb(void *param) { zvol_task_t *task = (zvol_task_t *)param; switch (task->op) { case ZVOL_ASYNC_CREATE_MINORS: (void) zvol_create_minors_impl(task->name1); break; case ZVOL_ASYNC_REMOVE_MINORS: zvol_remove_minors_impl(task->name1); break; case ZVOL_ASYNC_RENAME_MINORS: zvol_rename_minors_impl(task->name1, task->name2); break; case ZVOL_ASYNC_SET_SNAPDEV: zvol_set_snapdev_impl(task->name1, task->snapdev); break; default: VERIFY(0); break; } zvol_task_free(task); } typedef struct zvol_set_snapdev_arg { const char *zsda_name; uint64_t zsda_value; zprop_source_t zsda_source; dmu_tx_t *zsda_tx; } zvol_set_snapdev_arg_t; /* * Sanity check the dataset for safe use by the sync task. No additional * conditions are imposed. */ static int zvol_set_snapdev_check(void *arg, dmu_tx_t *tx) { zvol_set_snapdev_arg_t *zsda = arg; dsl_pool_t *dp = dmu_tx_pool(tx); dsl_dir_t *dd; int error; error = dsl_dir_hold(dp, zsda->zsda_name, FTAG, &dd, NULL); if (error != 0) return (error); dsl_dir_rele(dd, FTAG); return (error); } /* ARGSUSED */ static int zvol_set_snapdev_sync_cb(dsl_pool_t *dp, dsl_dataset_t *ds, void *arg) { char dsname[MAXNAMELEN]; zvol_task_t *task; uint64_t snapdev; dsl_dataset_name(ds, dsname); if (dsl_prop_get_int_ds(ds, "snapdev", &snapdev) != 0) return (0); task = zvol_task_alloc(ZVOL_ASYNC_SET_SNAPDEV, dsname, NULL, snapdev); if (task == NULL) return (0); (void) taskq_dispatch(dp->dp_spa->spa_zvol_taskq, zvol_task_cb, task, TQ_SLEEP); return (0); } /* * Traverse all child datasets and apply snapdev appropriately. * We call dsl_prop_set_sync_impl() here to set the value only on the toplevel * dataset and read the effective "snapdev" on every child in the callback * function: this is because the value is not guaranteed to be the same in the * whole dataset hierarchy. */ static void zvol_set_snapdev_sync(void *arg, dmu_tx_t *tx) { zvol_set_snapdev_arg_t *zsda = arg; dsl_pool_t *dp = dmu_tx_pool(tx); dsl_dir_t *dd; dsl_dataset_t *ds; int error; VERIFY0(dsl_dir_hold(dp, zsda->zsda_name, FTAG, &dd, NULL)); zsda->zsda_tx = tx; error = dsl_dataset_hold(dp, zsda->zsda_name, FTAG, &ds); if (error == 0) { dsl_prop_set_sync_impl(ds, zfs_prop_to_name(ZFS_PROP_SNAPDEV), zsda->zsda_source, sizeof (zsda->zsda_value), 1, &zsda->zsda_value, zsda->zsda_tx); dsl_dataset_rele(ds, FTAG); } dmu_objset_find_dp(dp, dd->dd_object, zvol_set_snapdev_sync_cb, zsda, DS_FIND_CHILDREN); dsl_dir_rele(dd, FTAG); } int zvol_set_snapdev(const char *ddname, zprop_source_t source, uint64_t snapdev) { zvol_set_snapdev_arg_t zsda; zsda.zsda_name = ddname; zsda.zsda_source = source; zsda.zsda_value = snapdev; return (dsl_sync_task(ddname, zvol_set_snapdev_check, zvol_set_snapdev_sync, &zsda, 0, ZFS_SPACE_CHECK_NONE)); } void zvol_create_minors(spa_t *spa, const char *name, boolean_t async) { zvol_task_t *task; taskqid_t id; task = zvol_task_alloc(ZVOL_ASYNC_CREATE_MINORS, name, NULL, ~0ULL); if (task == NULL) return; id = taskq_dispatch(spa->spa_zvol_taskq, zvol_task_cb, task, TQ_SLEEP); if ((async == B_FALSE) && (id != TASKQID_INVALID)) taskq_wait_id(spa->spa_zvol_taskq, id); } void zvol_remove_minors(spa_t *spa, const char *name, boolean_t async) { zvol_task_t *task; taskqid_t id; task = zvol_task_alloc(ZVOL_ASYNC_REMOVE_MINORS, name, NULL, ~0ULL); if (task == NULL) return; id = taskq_dispatch(spa->spa_zvol_taskq, zvol_task_cb, task, TQ_SLEEP); if ((async == B_FALSE) && (id != TASKQID_INVALID)) taskq_wait_id(spa->spa_zvol_taskq, id); } void zvol_rename_minors(spa_t *spa, const char *name1, const char *name2, boolean_t async) { zvol_task_t *task; taskqid_t id; task = zvol_task_alloc(ZVOL_ASYNC_RENAME_MINORS, name1, name2, ~0ULL); if (task == NULL) return; id = taskq_dispatch(spa->spa_zvol_taskq, zvol_task_cb, task, TQ_SLEEP); if ((async == B_FALSE) && (id != TASKQID_INVALID)) taskq_wait_id(spa->spa_zvol_taskq, id); } int zvol_init(void) { int threads = MIN(MAX(zvol_threads, 1), 1024); int i, error; list_create(&zvol_state_list, sizeof (zvol_state_t), offsetof(zvol_state_t, zv_next)); mutex_init(&zvol_state_lock, NULL, MUTEX_DEFAULT, NULL); ida_init(&zvol_ida); zvol_taskq = taskq_create(ZVOL_DRIVER, threads, maxclsyspri, threads * 2, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC); if (zvol_taskq == NULL) { printk(KERN_INFO "ZFS: taskq_create() failed\n"); error = -ENOMEM; goto out; } zvol_htable = kmem_alloc(ZVOL_HT_SIZE * sizeof (struct hlist_head), KM_SLEEP); if (!zvol_htable) { error = -ENOMEM; goto out_taskq; } for (i = 0; i < ZVOL_HT_SIZE; i++) INIT_HLIST_HEAD(&zvol_htable[i]); error = register_blkdev(zvol_major, ZVOL_DRIVER); if (error) { printk(KERN_INFO "ZFS: register_blkdev() failed %d\n", error); goto out_free; } blk_register_region(MKDEV(zvol_major, 0), 1UL << MINORBITS, THIS_MODULE, zvol_probe, NULL, NULL); return (0); out_free: kmem_free(zvol_htable, ZVOL_HT_SIZE * sizeof (struct hlist_head)); out_taskq: taskq_destroy(zvol_taskq); out: ida_destroy(&zvol_ida); mutex_destroy(&zvol_state_lock); list_destroy(&zvol_state_list); return (SET_ERROR(error)); } void zvol_fini(void) { zvol_remove_minors_impl(NULL); blk_unregister_region(MKDEV(zvol_major, 0), 1UL << MINORBITS); unregister_blkdev(zvol_major, ZVOL_DRIVER); kmem_free(zvol_htable, ZVOL_HT_SIZE * sizeof (struct hlist_head)); taskq_destroy(zvol_taskq); list_destroy(&zvol_state_list); mutex_destroy(&zvol_state_lock); ida_destroy(&zvol_ida); } /* BEGIN CSTYLED */ module_param(zvol_inhibit_dev, uint, 0644); MODULE_PARM_DESC(zvol_inhibit_dev, "Do not create zvol device nodes"); module_param(zvol_major, uint, 0444); MODULE_PARM_DESC(zvol_major, "Major number for zvol device"); module_param(zvol_threads, uint, 0444); MODULE_PARM_DESC(zvol_threads, "Max number of threads to handle I/O requests"); module_param(zvol_request_sync, uint, 0644); MODULE_PARM_DESC(zvol_request_sync, "Synchronously handle bio requests"); module_param(zvol_max_discard_blocks, ulong, 0444); MODULE_PARM_DESC(zvol_max_discard_blocks, "Max number of blocks to discard"); module_param(zvol_prefetch_bytes, uint, 0644); MODULE_PARM_DESC(zvol_prefetch_bytes, "Prefetch N bytes at zvol start+end"); /* END CSTYLED */