patch-2.3.47 linux/drivers/block/lvm-snap.c

• Lines: 435
• Date: Thu Feb 17 16:13:05 2000
• Orig file: v2.3.46/linux/drivers/block/lvm-snap.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.3.46/linux/drivers/block/lvm-snap.c linux/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;
+	}
+}