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Old 03-01-2010, 11:23 PM
Mike Snitzer
 
Default dm-multisnap-mikulas-blocks

From: Mikulas Patocka <mpatocka@redhat.com>

Common operations with blocks.

Management of tmp_remap array and some helper functions.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
---
drivers/md/dm-multisnap-blocks.c | 333 ++++++++++++++++++++++++++++++++++++++
1 files changed, 333 insertions(+), 0 deletions(-)
create mode 100644 drivers/md/dm-multisnap-blocks.c

diff --git a/drivers/md/dm-multisnap-blocks.c b/drivers/md/dm-multisnap-blocks.c
new file mode 100644
index 0000000..8715ed9
--- /dev/null
+++ b/drivers/md/dm-multisnap-blocks.c
@@ -0,0 +1,333 @@
+/*
+ * Copyright (C) 2009 Red Hat Czech, s.r.o.
+ *
+ * Mikulas Patocka <mpatocka@redhat.com>
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm-multisnap-mikulas.h"
+
+/*
+ * Check that the block is valid.
+ */
+static int check_invalid(struct dm_exception_store *s, chunk_t block)
+{
+ if (unlikely(block >= s->dev_size) ||
+ unlikely(block == SB_BLOCK) ||
+ unlikely(dm_multisnap_is_commit_block(s, block))) {
+ DM_MULTISNAP_SET_ERROR(s->dm, -EFSERROR,
+ ("check_invalid: access to invalid part of the device: %llx, size %llx",
+ (unsigned long long)block, (unsigned long long)s->dev_size));
+ return 1;
+ }
+ return 0;
+}
+
+static struct tmp_remap *find_tmp_remap(struct dm_exception_store *s, chunk_t block)
+{
+ struct tmp_remap *t;
+ struct hlist_node *hn;
+ unsigned hash = TMP_REMAP_HASH(block);
+ hlist_for_each_entry(t, hn, &s->tmp_remap[hash], hash_list) {
+ if (t->old == block)
+ return t;
+ cond_resched();
+ }
+ return NULL;
+}
+
+/*
+ * Remap a block number according to tmp_remap table.
+ */
+chunk_t dm_multisnap_remap_block(struct dm_exception_store *s, chunk_t block)
+{
+ struct tmp_remap *t;
+ t = find_tmp_remap(s, block);
+ if (t)
+ return t->new;
+ return block;
+}
+
+/*
+ * Read a metadata block, return pointer to the dataand hold a buffer for that
+ * block.
+ *
+ * Do a possible block remapping according to tmp_remap table.
+ */
+void *dm_multisnap_read_block(struct dm_exception_store *s, chunk_t block,
+ struct dm_buffer **bp)
+{
+ void *buf;
+ cond_resched();
+
+ if (unlikely(check_invalid(s, block)))
+ return NULL;
+
+ block = dm_multisnap_remap_block(s, block);
+
+ if (unlikely(check_invalid(s, block)))
+ return NULL;
+
+ buf = dm_bufio_read(s->bufio, block, bp);
+ if (unlikely(IS_ERR(buf))) {
+ DM_MULTISNAP_SET_ERROR(s->dm, PTR_ERR(buf),
+ ("dm_multisnap_read_block: error read chunk %llx",
+ (unsigned long long)block));
+ return NULL;
+ }
+ return buf;
+}
+
+struct uncommitted_record {
+ struct hlist_node hash;
+ chunk_t block;
+};
+
+/*
+ * Check if the block is not yet committed.
+ *
+ * If this function returns 1, the block is surely uncommitted.
+ * If it returns 0, the block may be committed or may be uncommitted.
+ * This function is used for optimizations, if it returns 0
+ * it doesn't break correctness, it only degrades performance.
+ */
+int dm_multisnap_block_is_uncommitted(struct dm_exception_store *s, chunk_t block)
+{
+ struct tmp_remap *t;
+
+ struct uncommitted_record *ur;
+ struct hlist_node *hn;
+
+ check_invalid(s, block);
+ t = find_tmp_remap(s, block);
+ if (t) {
+ if (t->uncommitted)
+ return 1;
+ block = t->new;
+ }
+ hlist_for_each_entry(ur, hn, &s->uncommitted_blocks[UNCOMMITTED_BLOCK_HASH(block)], hash)
+ if (ur->block == block)
+ return 1;
+ return 0;
+}
+
+/*
+ * Set the given block as uncommitted.
+ *
+ * The allocation may fail, in this case we see only a performance degradation
+ * (the block will be copied again), there is no functionality loss.
+ *
+ * We can't use non-failing allocation because it could deadlock (wait for some
+ * pages being written and that write could be directed through this driver).
+ */
+void dm_multisnap_block_set_uncommitted(struct dm_exception_store *s, chunk_t block)
+{
+ struct uncommitted_record *ur;
+ /*
+ * GFP_ATOMIC allows to exhaust reserves. We don't want it (we can
+ * afford failure), so we use GFP_NOWAIT.
+ * __GFP_NOWARN supresses the log message on failure.
+ * __GFP_NOMEMALLOC makes it less aggressive if the allocator recurses
+ * into itself.
+ */
+ ur = kmalloc(sizeof(struct uncommitted_record),
+ GFP_NOWAIT | __GFP_NOWARN | __GFP_NOMEMALLOC);
+ if (!ur)
+ return;
+ ur->block = block;
+ hlist_add_head(&ur->hash, &s->uncommitted_blocks[UNCOMMITTED_BLOCK_HASH(block)]);
+}
+
+/*
+ * Clear the register of uncommitted blocks. This is called on commit and
+ * on unload.
+ */
+void dm_multisnap_clear_uncommitted(struct dm_exception_store *s)
+{
+ int i;
+ for (i = 0; i < UNCOMMITTED_BLOCK_HASH_SIZE; i++) {
+ struct hlist_head *h = &s->uncommitted_blocks[i];
+ while (!hlist_empty(h)) {
+ struct uncommitted_record *ur =
+ hlist_entry(h->first, struct uncommitted_record, hash);
+ hlist_del(&ur->hash);
+ kfree(ur);
+ }
+ }
+}
+
+/*
+ * This function is called by an allocation code when needing to modify a
+ * committed block.
+ *
+ * It will create new remap for old_chunk->new_chunk.
+ * bitmap_idx is the index of bitmap if we are remapping bitmap, otherwise
+ * CB_BITMAP_IDX_NONE.
+ *
+ * *bp must be open buffer for old_chunk. New buffer for new_chunk is returned
+ * there.
+ *
+ * A block that needs to be freed is returned in to_free. If to_free is NULL,
+ * that block is freed immediatelly.
+ */
+void *dm_multisnap_duplicate_block(struct dm_exception_store *s, chunk_t old_chunk,
+ chunk_t new_chunk, bitmap_t bitmap_idx,
+ struct dm_buffer **bp, chunk_t *to_free_ptr)
+{
+ chunk_t to_free_val;
+ void *buf;
+ struct tmp_remap *t;
+
+ if (unlikely(check_invalid(s, old_chunk)) ||
+ unlikely(check_invalid(s, new_chunk)))
+ return NULL;
+
+ if (!to_free_ptr)
+ to_free_ptr = &to_free_val;
+ *to_free_ptr = 0;
+
+ t = find_tmp_remap(s, old_chunk);
+ if (t) {
+ if (unlikely(t->bitmap_idx != bitmap_idx)) {
+ DM_MULTISNAP_SET_ERROR(s->dm, -EFSERROR,
+ ("dm_multisnap_duplicate_block: bitmap_idx doesn't match, %X != %X",
+ t->bitmap_idx, bitmap_idx));
+ return NULL;
+ }
+ *to_free_ptr = t->new;
+ t->new = new_chunk;
+ } else {
+ if (unlikely(list_empty(&s->free_tmp_remaps))) {
+ DM_MULTISNAP_SET_ERROR(s->dm, -EFSERROR,
+ ("dm_multisnap_duplicate_block: all remap blocks used"));
+ return NULL;
+ }
+ t = list_first_entry(&s->free_tmp_remaps, struct tmp_remap, list);
+ t->new = new_chunk;
+ t->old = old_chunk;
+ t->bitmap_idx = bitmap_idx;
+ hlist_add_head(&t->hash_list, &s->tmp_remap[TMP_REMAP_HASH(old_chunk)]);
+ s->n_used_tmp_remaps++;
+ }
+ list_del(&t->list);
+ if (bitmap_idx == CB_BITMAP_IDX_NONE)
+ list_add_tail(&t->list, &s->used_bt_tmp_remaps);
+ else
+ list_add_tail(&t->list, &s->used_bitmap_tmp_remaps);
+ t->uncommitted = 1;
+ dm_bufio_release_move(*bp, new_chunk);
+
+ if (to_free_ptr == &to_free_val && to_free_val)
+ dm_multisnap_free_block(s, to_free_val, 0);
+
+ buf = dm_bufio_read(s->bufio, new_chunk, bp);
+ if (IS_ERR(buf)) {
+ DM_MULTISNAP_SET_ERROR(s->dm, PTR_ERR(buf),
+ ("dm_multisnap_duplicate_block: error reading chunk %llx",
+ (unsigned long long)new_chunk));
+ return NULL;
+ }
+ return buf;
+}
+
+/*
+ * Remove an entry from tmp_remap table.
+ */
+void dm_multisnap_free_tmp_remap(struct dm_exception_store *s, struct tmp_remap *t)
+{
+ list_del(&t->list);
+ hlist_del(&t->hash_list);
+ s->n_used_tmp_remaps--;
+ list_add(&t->list, &s->free_tmp_remaps);
+}
+
+/*
+ * Get a new block. Just a wrapper around dm_bufio_new.
+ * It is expected that the caller fills all the data in the block, calls
+ * dm_bufio_mark_buffer_dirty and releases the buffer.
+ */
+void *dm_multisnap_make_block(struct dm_exception_store *s, chunk_t new_chunk,
+ struct dm_buffer **bp)
+{
+ void *buf;
+
+ if (unlikely(check_invalid(s, new_chunk)))
+ return NULL;
+
+ dm_multisnap_block_set_uncommitted(s, new_chunk);
+
+ buf = dm_bufio_new(s->bufio, new_chunk, bp);
+ if (unlikely(IS_ERR(buf))) {
+ DM_MULTISNAP_SET_ERROR(s->dm, PTR_ERR(buf),
+ ("dm_multisnap_make_block: error creating new block at chunk %llx",
+ (unsigned long long)new_chunk));
+ return NULL;
+ }
+ return buf;
+}
+
+/*
+ * Free the given block and a possible tmp_remap shadow of it.
+ */
+void dm_multisnap_free_block_and_duplicates(struct dm_exception_store *s, chunk_t block)
+{
+ struct tmp_remap *t;
+
+ if (unlikely(check_invalid(s, block)))
+ return;
+
+ t = find_tmp_remap(s, block);
+ if (t) {
+ dm_multisnap_free_block(s, t->new, 0);
+ dm_multisnap_free_tmp_remap(s, t);
+ }
+ dm_multisnap_free_block(s, block, 0);
+}
+
+/*
+ * Return true if the block is a commit block.
+ */
+int dm_multisnap_is_commit_block(struct dm_exception_store *s, chunk_t block)
+{
+ if (unlikely(block < FIRST_CB_BLOCK))
+ return 0;
+ /*
+ * Division is very slow, thus we optimize the most common case
+ * if cb_stride is the power of 2.
+ */
+ if (likely(!(s->cb_stride & (s->cb_stride - 1))))
+ return (block & (s->cb_stride - 1)) == (FIRST_CB_BLOCK & (s->cb_stride - 1));
+ else
+ return sector_div(block, s->cb_stride) == FIRST_CB_BLOCK % s->cb_stride;
+}
+
+/*
+ * These two functions are used to avoid cycling on a corrupted device.
+ *
+ * If the data on the device is corrupted, we mark the device as errorneous,
+ * but we don't want to lockup the whole system. These functions help to achieve
+ * this goal.
+ *
+ * cy->count is the number of processed blocks.
+ * cy->key is the recorded block at last power-of-two count.
+ */
+void dm_multisnap_init_stop_cycles(struct stop_cycles *cy)
+{
+ cy->key = 0;
+ cy->count = 0;
+}
+
+int dm_multisnap_stop_cycles(struct dm_exception_store *s, struct stop_cycles *cy, chunk_t key)
+{
+ if (unlikely(cy->key == key) && unlikely(cy->count != 0)) {
+ DM_MULTISNAP_SET_ERROR(s->dm, -EFSERROR,
+ ("dm_multisnap_stop_cycles: cycle detected at chunk %llx",
+ (unsigned long long)key));
+ return -1;
+ }
+ cy->count++;
+ if (!((cy->count - 1) & cy->count))
+ cy->key = key;
+ return 0;
+}
--
1.6.5.2

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