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927ffe7c9a
When suspending a device-mapper device, dm_suspend() sleeps until all necessary I/O is completed. This state is triggered by a callback from persistent_commit(). But some I/O can still be issued *after* the callback (to prepare the next metadata area for use if the current one is full). This patch delays the callback until after that I/O is complete. Signed-off-by: Mark McLoughlin <markmc@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
665 lines
15 KiB
C
665 lines
15 KiB
C
/*
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* dm-snapshot.c
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*
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* Copyright (C) 2001-2002 Sistina Software (UK) Limited.
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*
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* This file is released under the GPL.
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*/
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#include "dm.h"
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#include "dm-snap.h"
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#include "dm-io.h"
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#include "kcopyd.h"
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#include <linux/mm.h>
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#include <linux/pagemap.h>
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#include <linux/vmalloc.h>
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#include <linux/slab.h>
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#define DM_MSG_PREFIX "snapshots"
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#define DM_CHUNK_SIZE_DEFAULT_SECTORS 32 /* 16KB */
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/*-----------------------------------------------------------------
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* Persistent snapshots, by persistent we mean that the snapshot
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* will survive a reboot.
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*---------------------------------------------------------------*/
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/*
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* We need to store a record of which parts of the origin have
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* been copied to the snapshot device. The snapshot code
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* requires that we copy exception chunks to chunk aligned areas
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* of the COW store. It makes sense therefore, to store the
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* metadata in chunk size blocks.
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*
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* There is no backward or forward compatibility implemented,
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* snapshots with different disk versions than the kernel will
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* not be usable. It is expected that "lvcreate" will blank out
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* the start of a fresh COW device before calling the snapshot
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* constructor.
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*
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* The first chunk of the COW device just contains the header.
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* After this there is a chunk filled with exception metadata,
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* followed by as many exception chunks as can fit in the
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* metadata areas.
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*
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* All on disk structures are in little-endian format. The end
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* of the exceptions info is indicated by an exception with a
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* new_chunk of 0, which is invalid since it would point to the
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* header chunk.
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*/
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/*
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* Magic for persistent snapshots: "SnAp" - Feeble isn't it.
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*/
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#define SNAP_MAGIC 0x70416e53
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/*
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* The on-disk version of the metadata.
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*/
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#define SNAPSHOT_DISK_VERSION 1
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struct disk_header {
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uint32_t magic;
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/*
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* Is this snapshot valid. There is no way of recovering
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* an invalid snapshot.
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*/
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uint32_t valid;
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/*
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* Simple, incrementing version. no backward
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* compatibility.
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*/
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uint32_t version;
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/* In sectors */
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uint32_t chunk_size;
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};
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struct disk_exception {
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uint64_t old_chunk;
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uint64_t new_chunk;
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};
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struct commit_callback {
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void (*callback)(void *, int success);
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void *context;
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};
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/*
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* The top level structure for a persistent exception store.
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*/
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struct pstore {
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struct dm_snapshot *snap; /* up pointer to my snapshot */
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int version;
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int valid;
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uint32_t exceptions_per_area;
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/*
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* Now that we have an asynchronous kcopyd there is no
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* need for large chunk sizes, so it wont hurt to have a
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* whole chunks worth of metadata in memory at once.
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*/
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void *area;
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/*
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* Used to keep track of which metadata area the data in
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* 'chunk' refers to.
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*/
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uint32_t current_area;
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/*
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* The next free chunk for an exception.
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*/
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uint32_t next_free;
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/*
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* The index of next free exception in the current
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* metadata area.
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*/
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uint32_t current_committed;
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atomic_t pending_count;
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uint32_t callback_count;
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struct commit_callback *callbacks;
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};
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static inline unsigned int sectors_to_pages(unsigned int sectors)
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{
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return sectors / (PAGE_SIZE >> 9);
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}
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static int alloc_area(struct pstore *ps)
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{
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int r = -ENOMEM;
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size_t len;
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len = ps->snap->chunk_size << SECTOR_SHIFT;
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/*
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* Allocate the chunk_size block of memory that will hold
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* a single metadata area.
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*/
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ps->area = vmalloc(len);
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if (!ps->area)
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return r;
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return 0;
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}
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static void free_area(struct pstore *ps)
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{
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vfree(ps->area);
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ps->area = NULL;
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}
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/*
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* Read or write a chunk aligned and sized block of data from a device.
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*/
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static int chunk_io(struct pstore *ps, uint32_t chunk, int rw)
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{
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struct io_region where;
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unsigned long bits;
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where.bdev = ps->snap->cow->bdev;
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where.sector = ps->snap->chunk_size * chunk;
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where.count = ps->snap->chunk_size;
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return dm_io_sync_vm(1, &where, rw, ps->area, &bits);
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}
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/*
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* Read or write a metadata area. Remembering to skip the first
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* chunk which holds the header.
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*/
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static int area_io(struct pstore *ps, uint32_t area, int rw)
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{
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int r;
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uint32_t chunk;
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/* convert a metadata area index to a chunk index */
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chunk = 1 + ((ps->exceptions_per_area + 1) * area);
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r = chunk_io(ps, chunk, rw);
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if (r)
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return r;
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ps->current_area = area;
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return 0;
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}
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static int zero_area(struct pstore *ps, uint32_t area)
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{
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memset(ps->area, 0, ps->snap->chunk_size << SECTOR_SHIFT);
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return area_io(ps, area, WRITE);
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}
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static int read_header(struct pstore *ps, int *new_snapshot)
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{
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int r;
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struct disk_header *dh;
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chunk_t chunk_size;
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int chunk_size_supplied = 1;
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/*
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* Use default chunk size (or hardsect_size, if larger) if none supplied
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*/
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if (!ps->snap->chunk_size) {
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ps->snap->chunk_size = max(DM_CHUNK_SIZE_DEFAULT_SECTORS,
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bdev_hardsect_size(ps->snap->cow->bdev) >> 9);
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ps->snap->chunk_mask = ps->snap->chunk_size - 1;
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ps->snap->chunk_shift = ffs(ps->snap->chunk_size) - 1;
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chunk_size_supplied = 0;
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}
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r = dm_io_get(sectors_to_pages(ps->snap->chunk_size));
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if (r)
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return r;
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r = alloc_area(ps);
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if (r)
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goto bad1;
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r = chunk_io(ps, 0, READ);
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if (r)
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goto bad2;
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dh = (struct disk_header *) ps->area;
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if (le32_to_cpu(dh->magic) == 0) {
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*new_snapshot = 1;
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return 0;
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}
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if (le32_to_cpu(dh->magic) != SNAP_MAGIC) {
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DMWARN("Invalid or corrupt snapshot");
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r = -ENXIO;
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goto bad2;
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}
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*new_snapshot = 0;
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ps->valid = le32_to_cpu(dh->valid);
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ps->version = le32_to_cpu(dh->version);
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chunk_size = le32_to_cpu(dh->chunk_size);
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if (!chunk_size_supplied || ps->snap->chunk_size == chunk_size)
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return 0;
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DMWARN("chunk size %llu in device metadata overrides "
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"table chunk size of %llu.",
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(unsigned long long)chunk_size,
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(unsigned long long)ps->snap->chunk_size);
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/* We had a bogus chunk_size. Fix stuff up. */
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dm_io_put(sectors_to_pages(ps->snap->chunk_size));
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free_area(ps);
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ps->snap->chunk_size = chunk_size;
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ps->snap->chunk_mask = chunk_size - 1;
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ps->snap->chunk_shift = ffs(chunk_size) - 1;
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r = dm_io_get(sectors_to_pages(chunk_size));
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if (r)
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return r;
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r = alloc_area(ps);
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if (r)
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goto bad1;
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return 0;
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bad2:
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free_area(ps);
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bad1:
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dm_io_put(sectors_to_pages(ps->snap->chunk_size));
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return r;
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}
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static int write_header(struct pstore *ps)
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{
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struct disk_header *dh;
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memset(ps->area, 0, ps->snap->chunk_size << SECTOR_SHIFT);
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dh = (struct disk_header *) ps->area;
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dh->magic = cpu_to_le32(SNAP_MAGIC);
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dh->valid = cpu_to_le32(ps->valid);
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dh->version = cpu_to_le32(ps->version);
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dh->chunk_size = cpu_to_le32(ps->snap->chunk_size);
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return chunk_io(ps, 0, WRITE);
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}
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/*
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* Access functions for the disk exceptions, these do the endian conversions.
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*/
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static struct disk_exception *get_exception(struct pstore *ps, uint32_t index)
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{
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BUG_ON(index >= ps->exceptions_per_area);
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return ((struct disk_exception *) ps->area) + index;
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}
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static void read_exception(struct pstore *ps,
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uint32_t index, struct disk_exception *result)
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{
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struct disk_exception *e = get_exception(ps, index);
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/* copy it */
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result->old_chunk = le64_to_cpu(e->old_chunk);
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result->new_chunk = le64_to_cpu(e->new_chunk);
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}
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static void write_exception(struct pstore *ps,
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uint32_t index, struct disk_exception *de)
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{
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struct disk_exception *e = get_exception(ps, index);
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/* copy it */
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e->old_chunk = cpu_to_le64(de->old_chunk);
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e->new_chunk = cpu_to_le64(de->new_chunk);
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}
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/*
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* Registers the exceptions that are present in the current area.
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* 'full' is filled in to indicate if the area has been
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* filled.
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*/
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static int insert_exceptions(struct pstore *ps, int *full)
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{
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int r;
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unsigned int i;
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struct disk_exception de;
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/* presume the area is full */
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*full = 1;
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for (i = 0; i < ps->exceptions_per_area; i++) {
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read_exception(ps, i, &de);
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/*
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* If the new_chunk is pointing at the start of
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* the COW device, where the first metadata area
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* is we know that we've hit the end of the
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* exceptions. Therefore the area is not full.
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*/
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if (de.new_chunk == 0LL) {
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ps->current_committed = i;
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*full = 0;
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break;
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}
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/*
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* Keep track of the start of the free chunks.
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*/
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if (ps->next_free <= de.new_chunk)
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ps->next_free = de.new_chunk + 1;
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/*
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* Otherwise we add the exception to the snapshot.
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*/
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r = dm_add_exception(ps->snap, de.old_chunk, de.new_chunk);
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if (r)
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return r;
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}
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return 0;
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}
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static int read_exceptions(struct pstore *ps)
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{
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uint32_t area;
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int r, full = 1;
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/*
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* Keeping reading chunks and inserting exceptions until
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* we find a partially full area.
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*/
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for (area = 0; full; area++) {
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r = area_io(ps, area, READ);
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if (r)
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return r;
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r = insert_exceptions(ps, &full);
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if (r)
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return r;
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}
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return 0;
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}
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static inline struct pstore *get_info(struct exception_store *store)
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{
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return (struct pstore *) store->context;
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}
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static void persistent_fraction_full(struct exception_store *store,
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sector_t *numerator, sector_t *denominator)
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{
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*numerator = get_info(store)->next_free * store->snap->chunk_size;
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*denominator = get_dev_size(store->snap->cow->bdev);
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}
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static void persistent_destroy(struct exception_store *store)
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{
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struct pstore *ps = get_info(store);
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dm_io_put(sectors_to_pages(ps->snap->chunk_size));
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vfree(ps->callbacks);
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free_area(ps);
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kfree(ps);
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}
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static int persistent_read_metadata(struct exception_store *store)
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{
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int r, new_snapshot;
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struct pstore *ps = get_info(store);
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/*
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* Read the snapshot header.
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*/
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r = read_header(ps, &new_snapshot);
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if (r)
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return r;
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/*
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* Now we know correct chunk_size, complete the initialisation.
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*/
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ps->exceptions_per_area = (ps->snap->chunk_size << SECTOR_SHIFT) /
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sizeof(struct disk_exception);
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ps->callbacks = dm_vcalloc(ps->exceptions_per_area,
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sizeof(*ps->callbacks));
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if (!ps->callbacks)
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return -ENOMEM;
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/*
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* Do we need to setup a new snapshot ?
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*/
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if (new_snapshot) {
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r = write_header(ps);
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if (r) {
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DMWARN("write_header failed");
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return r;
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}
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r = zero_area(ps, 0);
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if (r) {
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DMWARN("zero_area(0) failed");
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return r;
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}
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} else {
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/*
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* Sanity checks.
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*/
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if (!ps->valid) {
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DMWARN("snapshot is marked invalid");
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return -EINVAL;
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}
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if (ps->version != SNAPSHOT_DISK_VERSION) {
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DMWARN("unable to handle snapshot disk version %d",
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ps->version);
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return -EINVAL;
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}
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/*
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* Read the metadata.
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*/
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r = read_exceptions(ps);
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if (r)
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return r;
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}
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return 0;
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}
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static int persistent_prepare(struct exception_store *store,
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struct exception *e)
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{
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struct pstore *ps = get_info(store);
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uint32_t stride;
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sector_t size = get_dev_size(store->snap->cow->bdev);
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/* Is there enough room ? */
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if (size < ((ps->next_free + 1) * store->snap->chunk_size))
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return -ENOSPC;
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e->new_chunk = ps->next_free;
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/*
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* Move onto the next free pending, making sure to take
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* into account the location of the metadata chunks.
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*/
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stride = (ps->exceptions_per_area + 1);
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if ((++ps->next_free % stride) == 1)
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ps->next_free++;
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atomic_inc(&ps->pending_count);
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return 0;
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}
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static void persistent_commit(struct exception_store *store,
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struct exception *e,
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void (*callback) (void *, int success),
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void *callback_context)
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{
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int r;
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unsigned int i;
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struct pstore *ps = get_info(store);
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struct disk_exception de;
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struct commit_callback *cb;
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de.old_chunk = e->old_chunk;
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de.new_chunk = e->new_chunk;
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write_exception(ps, ps->current_committed++, &de);
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/*
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* Add the callback to the back of the array. This code
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* is the only place where the callback array is
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* manipulated, and we know that it will never be called
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* multiple times concurrently.
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*/
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cb = ps->callbacks + ps->callback_count++;
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cb->callback = callback;
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cb->context = callback_context;
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/*
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* If there are no more exceptions in flight, or we have
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* filled this metadata area we commit the exceptions to
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* disk.
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*/
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if (atomic_dec_and_test(&ps->pending_count) ||
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(ps->current_committed == ps->exceptions_per_area)) {
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r = area_io(ps, ps->current_area, WRITE);
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if (r)
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ps->valid = 0;
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/*
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* Have we completely filled the current area ?
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*/
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if (ps->current_committed == ps->exceptions_per_area) {
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ps->current_committed = 0;
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r = zero_area(ps, ps->current_area + 1);
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if (r)
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ps->valid = 0;
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}
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for (i = 0; i < ps->callback_count; i++) {
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cb = ps->callbacks + i;
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cb->callback(cb->context, r == 0 ? 1 : 0);
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}
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ps->callback_count = 0;
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}
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}
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static void persistent_drop(struct exception_store *store)
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{
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struct pstore *ps = get_info(store);
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ps->valid = 0;
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if (write_header(ps))
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DMWARN("write header failed");
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}
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|
int dm_create_persistent(struct exception_store *store)
|
|
{
|
|
struct pstore *ps;
|
|
|
|
/* allocate the pstore */
|
|
ps = kmalloc(sizeof(*ps), GFP_KERNEL);
|
|
if (!ps)
|
|
return -ENOMEM;
|
|
|
|
ps->snap = store->snap;
|
|
ps->valid = 1;
|
|
ps->version = SNAPSHOT_DISK_VERSION;
|
|
ps->area = NULL;
|
|
ps->next_free = 2; /* skipping the header and first area */
|
|
ps->current_committed = 0;
|
|
|
|
ps->callback_count = 0;
|
|
atomic_set(&ps->pending_count, 0);
|
|
ps->callbacks = NULL;
|
|
|
|
store->destroy = persistent_destroy;
|
|
store->read_metadata = persistent_read_metadata;
|
|
store->prepare_exception = persistent_prepare;
|
|
store->commit_exception = persistent_commit;
|
|
store->drop_snapshot = persistent_drop;
|
|
store->fraction_full = persistent_fraction_full;
|
|
store->context = ps;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*-----------------------------------------------------------------
|
|
* Implementation of the store for non-persistent snapshots.
|
|
*---------------------------------------------------------------*/
|
|
struct transient_c {
|
|
sector_t next_free;
|
|
};
|
|
|
|
static void transient_destroy(struct exception_store *store)
|
|
{
|
|
kfree(store->context);
|
|
}
|
|
|
|
static int transient_read_metadata(struct exception_store *store)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
static int transient_prepare(struct exception_store *store, struct exception *e)
|
|
{
|
|
struct transient_c *tc = (struct transient_c *) store->context;
|
|
sector_t size = get_dev_size(store->snap->cow->bdev);
|
|
|
|
if (size < (tc->next_free + store->snap->chunk_size))
|
|
return -1;
|
|
|
|
e->new_chunk = sector_to_chunk(store->snap, tc->next_free);
|
|
tc->next_free += store->snap->chunk_size;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void transient_commit(struct exception_store *store,
|
|
struct exception *e,
|
|
void (*callback) (void *, int success),
|
|
void *callback_context)
|
|
{
|
|
/* Just succeed */
|
|
callback(callback_context, 1);
|
|
}
|
|
|
|
static void transient_fraction_full(struct exception_store *store,
|
|
sector_t *numerator, sector_t *denominator)
|
|
{
|
|
*numerator = ((struct transient_c *) store->context)->next_free;
|
|
*denominator = get_dev_size(store->snap->cow->bdev);
|
|
}
|
|
|
|
int dm_create_transient(struct exception_store *store)
|
|
{
|
|
struct transient_c *tc;
|
|
|
|
store->destroy = transient_destroy;
|
|
store->read_metadata = transient_read_metadata;
|
|
store->prepare_exception = transient_prepare;
|
|
store->commit_exception = transient_commit;
|
|
store->drop_snapshot = NULL;
|
|
store->fraction_full = transient_fraction_full;
|
|
|
|
tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
|
|
if (!tc)
|
|
return -ENOMEM;
|
|
|
|
tc->next_free = 0;
|
|
store->context = tc;
|
|
|
|
return 0;
|
|
}
|