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/*
* kernel/lvm-snap.c
*
* Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
* Heinz Mauelshagen, Sistina Software (persistent snapshots)
*
* 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 snapshot 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.
*
*/
/*
* Changelog
*
* 05/07/2000 - implemented persistent snapshot support
* 23/11/2000 - used cpu_to_le64 rather than my own macro
* 25/01/2001 - Put LockPage back in
* 01/02/2001 - A dropped snapshot is now set as inactive
* 12/03/2001 - lvm_pv_get_number changes:
* o made it static
* o renamed it to _pv_get_number
* o pv number is returned in new uint * arg
* o -1 returned on error
* lvm_snapshot_fill_COW_table has a return value too.
*
*/
#include <linux/kernel.h>
#include <linux/module.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>
#include "lvm-internal.h"
static char *lvm_snap_version __attribute__ ((unused)) =
"LVM "LVM_RELEASE_NAME" snapshot code ("LVM_RELEASE_DATE")\n";
extern const char *const lvm_name;
extern int lvm_blocksizes[];
void lvm_snapshot_release(lv_t *);
static int _write_COW_table_block(vg_t *vg, lv_t *lv, int idx,
const char **reason);
static void _disable_snapshot(vg_t *vg, lv_t *lv);
static int _pv_get_number(vg_t * vg, kdev_t rdev, uint *pvn) {
uint p;
for(p = 0; p < vg->pv_max; p++) {
if(vg->pv[p] == NULL)
continue;
if(vg->pv[p]->pv_dev == rdev)
break;
}
if(p >= vg->pv_max) {
/* bad news, the snapshot COW table is probably corrupt */
printk(KERN_ERR
"%s -- _pv_get_number failed for rdev = %u\n",
lvm_name, rdev);
return -1;
}
*pvn = vg->pv[p]->pv_number;
return 0;
}
#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;
}
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;
}
void lvm_drop_snapshot(vg_t *vg, 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);
/* wipe the snapshot since it's inconsistent now */
_disable_snapshot(vg, lv_snap);
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);
lv_snap->lv_status &= ~LV_ACTIVE;
printk(KERN_INFO
"%s -- giving up to snapshot %s on %s: %s\n",
lvm_name, lv_snap->lv_snapshot_org->lv_name, lv_snap->lv_name,
reason);
}
static inline int 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 / SECTOR_SIZE;
if(start & (sectors_per_block - 1))
return 0;
nr_blocks = nr_sectors / sectors_per_block;
start /= sectors_per_block;
for (i = 0; i < nr_blocks; i++)
blocks[i] = start++;
return 1;
}
inline int lvm_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
int lvm_snapshot_fill_COW_page(vg_t * vg, lv_t * lv_snap)
{
uint pvn;
int id = 0, is = lv_snap->lv_remap_ptr;
ulong blksize_snap;
lv_COW_table_disk_t * lv_COW_table = (lv_COW_table_disk_t *)
page_address(lv_snap->lv_COW_table_iobuf->maplist[0]);
if (is == 0)
return 0;
is--;
blksize_snap =
lvm_get_blksize(lv_snap->lv_block_exception[is].rdev_new);
is -= is % (blksize_snap / sizeof(lv_COW_table_disk_t));
memset(lv_COW_table, 0, blksize_snap);
for ( ; is < lv_snap->lv_remap_ptr; is++, id++) {
/* store new COW_table entry */
lv_block_exception_t *be = lv_snap->lv_block_exception + is;
if(_pv_get_number(vg, be->rdev_org, &pvn))
goto bad;
lv_COW_table[id].pv_org_number = cpu_to_le64(pvn);
lv_COW_table[id].pv_org_rsector = cpu_to_le64(be->rsector_org);
if(_pv_get_number(vg, be->rdev_new, &pvn))
goto bad;
lv_COW_table[id].pv_snap_number = cpu_to_le64(pvn);
lv_COW_table[id].pv_snap_rsector =
cpu_to_le64(be->rsector_new);
}
return 0;
bad:
printk(KERN_ERR "%s -- lvm_snapshot_fill_COW_page failed", lvm_name);
return -1;
}
/*
* writes a COW exception table sector to disk (HM)
*/
int lvm_write_COW_table_block(vg_t * vg, lv_t *lv_snap)
{
int r;
const char *err;
if((r = _write_COW_table_block(vg, lv_snap,
lv_snap->lv_remap_ptr - 1, &err)))
lvm_drop_snapshot(vg, lv_snap, err);
return r;
}
/*
* 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,
vg_t *vg, 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;
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 %s faulting %lu start %lu, snap %s start %lu, "
"size %d, pe_start %lu pe_off %lu, virt_sec %lu\n",
lvm_name,
kdevname(org_phys_dev), org_phys_sector, org_start,
kdevname(snap_phys_dev), snap_start,
chunk_size,
org_pe_start, pe_off,
org_virt_sector);
#endif
iobuf = lv_snap->lv_iobuf;
blksize_org = lvm_get_blksize(org_phys_dev);
blksize_snap = lvm_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;
if(!lvm_snapshot_prepare_blocks(iobuf->blocks, org_start,
nr_sectors, blksize_org))
goto fail_prepare;
if (brw_kiovec(READ, 1, &iobuf, org_phys_dev,
iobuf->blocks, blksize_org) != (nr_sectors<<9))
goto fail_raw_read;
if(!lvm_snapshot_prepare_blocks(iobuf->blocks, snap_start,
nr_sectors, blksize_snap))
goto fail_prepare;
if (brw_kiovec(WRITE, 1, &iobuf, snap_phys_dev,
iobuf->blocks, blksize_snap) != (nr_sectors<<9))
goto fail_raw_write;
}
#ifdef DEBUG_SNAPSHOT
/* invalidate the logical 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;
if (lv_snap->lv_snapshot_use_rate > 0) {
if (lv_snap->lv_remap_ptr * 100 / lv_snap->lv_remap_end >= lv_snap->lv_snapshot_use_rate)
wake_up_interruptible(&lv_snap->lv_snapshot_wait);
}
return 0;
/* slow path */
out:
lvm_drop_snapshot(vg, 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;
fail_prepare:
reason = "couldn't prepare kiovec blocks "
"(start probably isn't block aligned)";
goto out;
}
int lvm_snapshot_alloc_iobuf_pages(struct kiobuf * iobuf, int sectors)
{
int bytes, nr_pages, err, i;
bytes = sectors * SECTOR_SIZE;
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;
page = alloc_page(GFP_KERNEL);
if (!page)
goto out;
iobuf->maplist[i] = page;
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;
}
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_table_size = size;
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 ret, max_sectors;
/* allocate kiovec to do chunk io */
ret = alloc_kiovec(1, &lv_snap->lv_iobuf);
if (ret) goto out;
max_sectors = KIO_MAX_SECTORS << (PAGE_SHIFT-9);
ret = lvm_snapshot_alloc_iobuf_pages(lv_snap->lv_iobuf, max_sectors);
if (ret) goto out_free_kiovec;
/* allocate kiovec to do exception table io */
ret = alloc_kiovec(1, &lv_snap->lv_COW_table_iobuf);
if (ret) goto out_free_kiovec;
ret = lvm_snapshot_alloc_iobuf_pages(lv_snap->lv_COW_table_iobuf,
PAGE_SIZE/SECTOR_SIZE);
if (ret) goto out_free_both_kiovecs;
ret = lvm_snapshot_alloc_hash_table(lv_snap);
if (ret) goto out_free_both_kiovecs;
out:
return ret;
out_free_both_kiovecs:
unmap_kiobuf(lv_snap->lv_COW_table_iobuf);
free_kiovec(1, &lv_snap->lv_COW_table_iobuf);
lv_snap->lv_COW_table_iobuf = NULL;
out_free_kiovec:
unmap_kiobuf(lv_snap->lv_iobuf);
free_kiovec(1, &lv_snap->lv_iobuf);
lv_snap->lv_iobuf = NULL;
if (lv_snap->lv_snapshot_hash_table != NULL)
vfree(lv_snap->lv_snapshot_hash_table);
lv_snap->lv_snapshot_hash_table = NULL;
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;
lv->lv_snapshot_hash_table_size = 0;
}
if (lv->lv_iobuf)
{
kiobuf_wait_for_io(lv->lv_iobuf);
unmap_kiobuf(lv->lv_iobuf);
free_kiovec(1, &lv->lv_iobuf);
lv->lv_iobuf = NULL;
}
if (lv->lv_COW_table_iobuf)
{
kiobuf_wait_for_io(lv->lv_COW_table_iobuf);
unmap_kiobuf(lv->lv_COW_table_iobuf);
free_kiovec(1, &lv->lv_COW_table_iobuf);
lv->lv_COW_table_iobuf = NULL;
}
}
static int _write_COW_table_block(vg_t *vg, lv_t *lv_snap,
int idx, const char **reason) {
int blksize_snap;
int end_of_table;
int idx_COW_table;
uint pvn;
ulong snap_pe_start, COW_table_sector_offset,
COW_entries_per_pe, COW_chunks_per_pe, COW_entries_per_block;
ulong blocks[1];
kdev_t snap_phys_dev;
lv_block_exception_t *be;
struct kiobuf * COW_table_iobuf = lv_snap->lv_COW_table_iobuf;
lv_COW_table_disk_t * lv_COW_table =
( lv_COW_table_disk_t *) page_address(lv_snap->lv_COW_table_iobuf->maplist[0]);
COW_chunks_per_pe = LVM_GET_COW_TABLE_CHUNKS_PER_PE(vg, lv_snap);
COW_entries_per_pe = LVM_GET_COW_TABLE_ENTRIES_PER_PE(vg, lv_snap);
/* get physical addresse of destination chunk */
snap_phys_dev = lv_snap->lv_block_exception[idx].rdev_new;
snap_pe_start = lv_snap->lv_block_exception[idx - (idx % COW_entries_per_pe)].rsector_new - lv_snap->lv_chunk_size;
blksize_snap = lvm_get_blksize(snap_phys_dev);
COW_entries_per_block = blksize_snap / sizeof(lv_COW_table_disk_t);
idx_COW_table = idx % COW_entries_per_pe % COW_entries_per_block;
if ( idx_COW_table == 0) memset(lv_COW_table, 0, blksize_snap);
/* sector offset into the on disk COW table */
COW_table_sector_offset = (idx % COW_entries_per_pe) / (SECTOR_SIZE / sizeof(lv_COW_table_disk_t));
/* COW table block to write next */
blocks[0] = (snap_pe_start + COW_table_sector_offset) >> (blksize_snap >> 10);
/* store new COW_table entry */
be = lv_snap->lv_block_exception + idx;
if(_pv_get_number(vg, be->rdev_org, &pvn))
goto fail_pv_get_number;
lv_COW_table[idx_COW_table].pv_org_number = cpu_to_le64(pvn);
lv_COW_table[idx_COW_table].pv_org_rsector =
cpu_to_le64(be->rsector_org);
if(_pv_get_number(vg, snap_phys_dev, &pvn))
goto fail_pv_get_number;
lv_COW_table[idx_COW_table].pv_snap_number = cpu_to_le64(pvn);
lv_COW_table[idx_COW_table].pv_snap_rsector =
cpu_to_le64(be->rsector_new);
COW_table_iobuf->length = blksize_snap;
if (brw_kiovec(WRITE, 1, &COW_table_iobuf, snap_phys_dev,
blocks, blksize_snap) != blksize_snap)
goto fail_raw_write;
/* initialization of next COW exception table block with zeroes */
end_of_table = idx % COW_entries_per_pe == COW_entries_per_pe - 1;
if (idx_COW_table % COW_entries_per_block == COW_entries_per_block - 1 || end_of_table)
{
/* don't go beyond the end */
if (idx + 1 >= lv_snap->lv_remap_end) goto out;
memset(lv_COW_table, 0, blksize_snap);
if (end_of_table)
{
idx++;
snap_phys_dev = lv_snap->lv_block_exception[idx].rdev_new;
snap_pe_start = lv_snap->lv_block_exception[idx - (idx % COW_entries_per_pe)].rsector_new - lv_snap->lv_chunk_size;
blksize_snap = lvm_get_blksize(snap_phys_dev);
blocks[0] = snap_pe_start >> (blksize_snap >> 10);
} else blocks[0]++;
if (brw_kiovec(WRITE, 1, &COW_table_iobuf, snap_phys_dev,
blocks, blksize_snap) !=
blksize_snap)
goto fail_raw_write;
}
out:
return 0;
fail_raw_write:
*reason = "write error";
return 1;
fail_pv_get_number:
*reason = "_pv_get_number failed";
return 1;
}
/*
* FIXME_1.2
* This function is a bit of a hack; we need to ensure that the
* snapshot is never made active again, because it will surely be
* corrupt. At the moment we do not have access to the LVM metadata
* from within the kernel. So we set the first exception to point to
* sector 1 (which will always be within the metadata, and as such
* invalid). User land tools will check for this when they are asked
* to activate the snapshot and prevent this from happening.
*/
static void _disable_snapshot(vg_t *vg, lv_t *lv) {
const char *err;
lv->lv_block_exception[0].rsector_org = LVM_SNAPSHOT_DROPPED_SECTOR;
if(_write_COW_table_block(vg, lv, 0, &err) < 0) {
printk(KERN_ERR "%s -- couldn't disable snapshot: %s\n",
lvm_name, err);
}
}
MODULE_LICENSE("GPL");
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