diff options
Diffstat (limited to 'drivers/block/lvm-snap.c')
| -rw-r--r-- | drivers/block/lvm-snap.c | 434 |
1 files changed, 434 insertions, 0 deletions
diff --git a/drivers/block/lvm-snap.c b/drivers/block/lvm-snap.c new file mode 100644 index 000000000..77500cc43 --- /dev/null +++ b/drivers/block/lvm-snap.c @@ -0,0 +1,434 @@ +/* + * kernel/lvm-snap.c + * + * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE + * + * LVM snapshot driver is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2, or (at your option) + * any later version. + * + * LVM driver is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with GNU CC; see the file COPYING. If not, write to + * the Free Software Foundation, 59 Temple Place - Suite 330, + * Boston, MA 02111-1307, USA. + * + */ + +#include <linux/kernel.h> +#include <linux/vmalloc.h> +#include <linux/blkdev.h> +#include <linux/smp_lock.h> +#include <linux/types.h> +#include <linux/iobuf.h> +#include <linux/lvm.h> + + +static char *lvm_snap_version = "LVM 0.8final (15/02/2000)\n"; + +extern const char *const lvm_name; +extern int lvm_blocksizes[]; + +void lvm_snapshot_release(lv_t *); + +#define hashfn(dev,block,mask,chunk_size) \ + ((HASHDEV(dev)^((block)/(chunk_size))) & (mask)) + +static inline lv_block_exception_t * +lvm_find_exception_table(kdev_t org_dev, unsigned long org_start, lv_t * lv) +{ + struct list_head * hash_table = lv->lv_snapshot_hash_table, * next; + unsigned long mask = lv->lv_snapshot_hash_mask; + int chunk_size = lv->lv_chunk_size; + lv_block_exception_t * ret; + int i = 0; + + hash_table = &hash_table[hashfn(org_dev, org_start, mask, chunk_size)]; + ret = NULL; + for (next = hash_table->next; next != hash_table; next = next->next) + { + lv_block_exception_t * exception; + + exception = list_entry(next, lv_block_exception_t, hash); + if (exception->rsector_org == org_start && + exception->rdev_org == org_dev) + { + if (i) + { + /* fun, isn't it? :) */ + list_del(next); + list_add(next, hash_table); + } + ret = exception; + break; + } + i++; + } + return ret; +} + +static inline void lvm_hash_link(lv_block_exception_t * exception, + kdev_t org_dev, unsigned long org_start, + lv_t * lv) +{ + struct list_head * hash_table = lv->lv_snapshot_hash_table; + unsigned long mask = lv->lv_snapshot_hash_mask; + int chunk_size = lv->lv_chunk_size; + + hash_table = &hash_table[hashfn(org_dev, org_start, mask, chunk_size)]; + list_add(&exception->hash, hash_table); +} + +int lvm_snapshot_remap_block(kdev_t * org_dev, unsigned long * org_sector, + unsigned long pe_start, lv_t * lv) +{ + int ret; + unsigned long pe_off, pe_adjustment, __org_start; + kdev_t __org_dev; + int chunk_size = lv->lv_chunk_size; + lv_block_exception_t * exception; + + pe_off = pe_start % chunk_size; + pe_adjustment = (*org_sector-pe_off) % chunk_size; + __org_start = *org_sector - pe_adjustment; + __org_dev = *org_dev; + + ret = 0; + exception = lvm_find_exception_table(__org_dev, __org_start, lv); + if (exception) + { + *org_dev = exception->rdev_new; + *org_sector = exception->rsector_new + pe_adjustment; + ret = 1; + } + return ret; +} + +static void lvm_drop_snapshot(lv_t * lv_snap, const char * reason) +{ + kdev_t last_dev; + int i; + + /* no exception storage space available for this snapshot + or error on this snapshot --> release it */ + invalidate_buffers(lv_snap->lv_dev); + + for (i = last_dev = 0; i < lv_snap->lv_remap_ptr; i++) { + if ( lv_snap->lv_block_exception[i].rdev_new != last_dev) { + last_dev = lv_snap->lv_block_exception[i].rdev_new; + invalidate_buffers(last_dev); + } + } + + lvm_snapshot_release(lv_snap); + + printk(KERN_INFO + "%s -- giving up to snapshot %s on %s due %s\n", + lvm_name, lv_snap->lv_snapshot_org->lv_name, lv_snap->lv_name, + reason); +} + +static inline void lvm_snapshot_prepare_blocks(unsigned long * blocks, + unsigned long start, + int nr_sectors, + int blocksize) +{ + int i, sectors_per_block, nr_blocks; + + sectors_per_block = blocksize >> 9; + nr_blocks = nr_sectors / sectors_per_block; + start /= sectors_per_block; + + for (i = 0; i < nr_blocks; i++) + blocks[i] = start++; +} + +static inline int get_blksize(kdev_t dev) +{ + int correct_size = BLOCK_SIZE, i, major; + + major = MAJOR(dev); + if (blksize_size[major]) + { + i = blksize_size[major][MINOR(dev)]; + if (i) + correct_size = i; + } + return correct_size; +} + +#ifdef DEBUG_SNAPSHOT +static inline void invalidate_snap_cache(unsigned long start, unsigned long nr, + kdev_t dev) +{ + struct buffer_head * bh; + int sectors_per_block, i, blksize, minor; + + minor = MINOR(dev); + blksize = lvm_blocksizes[minor]; + sectors_per_block = blksize >> 9; + nr /= sectors_per_block; + start /= sectors_per_block; + + for (i = 0; i < nr; i++) + { + bh = get_hash_table(dev, start++, blksize); + if (bh) + bforget(bh); + } +} +#endif + +/* + * copy on write handler for one snapshot logical volume + * + * read the original blocks and store it/them on the new one(s). + * if there is no exception storage space free any longer --> release snapshot. + * + * this routine gets called for each _first_ write to a physical chunk. + */ +int lvm_snapshot_COW(kdev_t org_phys_dev, + unsigned long org_phys_sector, + unsigned long org_pe_start, + unsigned long org_virt_sector, + lv_t * lv_snap) +{ + const char * reason; + unsigned long org_start, snap_start, snap_phys_dev, virt_start, pe_off; + int idx = lv_snap->lv_remap_ptr, chunk_size = lv_snap->lv_chunk_size; + struct kiobuf * iobuf; + unsigned long blocks[KIO_MAX_SECTORS]; + int blksize_snap, blksize_org, min_blksize, max_blksize; + int max_sectors, nr_sectors; + + /* check if we are out of snapshot space */ + if (idx >= lv_snap->lv_remap_end) + goto fail_out_of_space; + + /* calculate physical boundaries of source chunk */ + pe_off = org_pe_start % chunk_size; + org_start = org_phys_sector - ((org_phys_sector-pe_off) % chunk_size); + virt_start = org_virt_sector - (org_phys_sector - org_start); + + /* calculate physical boundaries of destination chunk */ + snap_phys_dev = lv_snap->lv_block_exception[idx].rdev_new; + snap_start = lv_snap->lv_block_exception[idx].rsector_new; + +#ifdef DEBUG_SNAPSHOT + printk(KERN_INFO + "%s -- COW: " + "org %02d:%02d faulting %lu start %lu, " + "snap %02d:%02d start %lu, " + "size %d, pe_start %lu pe_off %lu, virt_sec %lu\n", + lvm_name, + MAJOR(org_phys_dev), MINOR(org_phys_dev), org_phys_sector, + org_start, + MAJOR(snap_phys_dev), MINOR(snap_phys_dev), snap_start, + chunk_size, + org_pe_start, pe_off, + org_virt_sector); +#endif + + iobuf = lv_snap->lv_iobuf; + + blksize_org = get_blksize(org_phys_dev); + blksize_snap = get_blksize(snap_phys_dev); + max_blksize = max(blksize_org, blksize_snap); + min_blksize = min(blksize_org, blksize_snap); + max_sectors = KIO_MAX_SECTORS * (min_blksize>>9); + + if (chunk_size % (max_blksize>>9)) + goto fail_blksize; + + while (chunk_size) + { + nr_sectors = min(chunk_size, max_sectors); + chunk_size -= nr_sectors; + + iobuf->length = nr_sectors << 9; + + lvm_snapshot_prepare_blocks(blocks, org_start, + nr_sectors, blksize_org); + if (brw_kiovec(READ, 1, &iobuf, org_phys_dev, + blocks, blksize_org) != (nr_sectors<<9)) + goto fail_raw_read; + + lvm_snapshot_prepare_blocks(blocks, snap_start, + nr_sectors, blksize_snap); + if (brw_kiovec(WRITE, 1, &iobuf, snap_phys_dev, + blocks, blksize_snap) != (nr_sectors<<9)) + goto fail_raw_write; + } + +#ifdef DEBUG_SNAPSHOT + /* invalidate the logcial snapshot buffer cache */ + invalidate_snap_cache(virt_start, lv_snap->lv_chunk_size, + lv_snap->lv_dev); +#endif + + /* the original chunk is now stored on the snapshot volume + so update the execption table */ + lv_snap->lv_block_exception[idx].rdev_org = org_phys_dev; + lv_snap->lv_block_exception[idx].rsector_org = org_start; + lvm_hash_link(lv_snap->lv_block_exception + idx, + org_phys_dev, org_start, lv_snap); + lv_snap->lv_remap_ptr = idx + 1; + return 0; + + /* slow path */ + out: + lvm_drop_snapshot(lv_snap, reason); + return 1; + + fail_out_of_space: + reason = "out of space"; + goto out; + fail_raw_read: + reason = "read error"; + goto out; + fail_raw_write: + reason = "write error"; + goto out; + fail_blksize: + reason = "blocksize error"; + goto out; +} + +static int lvm_snapshot_alloc_iobuf_pages(struct kiobuf * iobuf, int sectors) +{ + int bytes, nr_pages, err, i; + + bytes = sectors << 9; + nr_pages = (bytes + ~PAGE_MASK) >> PAGE_SHIFT; + err = expand_kiobuf(iobuf, nr_pages); + if (err) + goto out; + + err = -ENOMEM; + iobuf->locked = 1; + iobuf->nr_pages = 0; + for (i = 0; i < nr_pages; i++) + { + struct page * page; + +#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,3,27) + page = alloc_page(GFP_KERNEL); + if (!page) + goto out; +#else + { + unsigned long addr = __get_free_page(GFP_USER); + if (!addr) + goto out; + iobuf->pagelist[i] = addr; + page = mem_map + MAP_NR(addr); + } +#endif + + iobuf->maplist[i] = page; + /* the only point to lock the page here is to be allowed + to share unmap_kiobuf() in the fail-path */ +#ifndef LockPage +#define LockPage(map) set_bit(PG_locked, &(map)->flags) +#endif + LockPage(page); + iobuf->nr_pages++; + } + iobuf->offset = 0; + + err = 0; + out: + return err; +} + +static int calc_max_buckets(void) +{ + unsigned long mem; + + mem = num_physpages << PAGE_SHIFT; + mem /= 100; + mem *= 2; + mem /= sizeof(struct list_head); + + return mem; +} + +static int lvm_snapshot_alloc_hash_table(lv_t * lv) +{ + int err; + unsigned long buckets, max_buckets, size; + struct list_head * hash; + + buckets = lv->lv_remap_end; + max_buckets = calc_max_buckets(); + buckets = min(buckets, max_buckets); + while (buckets & (buckets-1)) + buckets &= (buckets-1); + + size = buckets * sizeof(struct list_head); + + err = -ENOMEM; + hash = vmalloc(size); + lv->lv_snapshot_hash_table = hash; + + if (!hash) + goto out; + + lv->lv_snapshot_hash_mask = buckets-1; + while (buckets--) + INIT_LIST_HEAD(hash+buckets); + err = 0; + out: + return err; +} + +int lvm_snapshot_alloc(lv_t * lv_snap) +{ + int err, blocksize, max_sectors; + + err = alloc_kiovec(1, &lv_snap->lv_iobuf); + if (err) + goto out; + + blocksize = lvm_blocksizes[MINOR(lv_snap->lv_dev)]; + max_sectors = KIO_MAX_SECTORS << (PAGE_SHIFT-9); + + err = lvm_snapshot_alloc_iobuf_pages(lv_snap->lv_iobuf, max_sectors); + if (err) + goto out_free_kiovec; + + err = lvm_snapshot_alloc_hash_table(lv_snap); + if (err) + goto out_free_kiovec; + out: + return err; + + out_free_kiovec: + unmap_kiobuf(lv_snap->lv_iobuf); + free_kiovec(1, &lv_snap->lv_iobuf); + goto out; +} + +void lvm_snapshot_release(lv_t * lv) +{ + if (lv->lv_block_exception) + { + vfree(lv->lv_block_exception); + lv->lv_block_exception = NULL; + } + if (lv->lv_snapshot_hash_table) + { + vfree(lv->lv_snapshot_hash_table); + lv->lv_snapshot_hash_table = NULL; + } + if (lv->lv_iobuf) + { + free_kiovec(1, &lv->lv_iobuf); + lv->lv_iobuf = NULL; + } +} |