]> git.ozlabs.org Git - ccan/blobdiff - ccan/tdb2/transaction.c
tdb2: use direct access functions when creating recovery blob
[ccan] / ccan / tdb2 / transaction.c
index 73ab1e39ff4ad0c4f260be0bf1dc6d9eca95bcd2..805ea0948aad0e0ddfa11289aadc26334cfc8a44 100644 (file)
@@ -88,7 +88,6 @@
     fsync/msync calls are made.
 */
 
-
 /*
   hold the context of any current transaction
 */
@@ -110,7 +109,7 @@ struct tdb_transaction {
        /* when inside a transaction we need to keep track of any
           nested tdb_transaction_start() calls, as these are allowed,
           but don't create a new transaction */
-       int nesting;
+       unsigned int nesting;
 
        /* set when a prepare has already occurred */
        bool prepared;
@@ -120,6 +119,8 @@ struct tdb_transaction {
        tdb_len_t old_map_size;
 };
 
+/* This doesn't really need to be pagesize, but we use it for similar reasons. */
+#define PAGESIZE 65536
 
 /*
   read while in a transaction. We need to check first if the data is in our list
@@ -132,8 +133,8 @@ static enum TDB_ERROR transaction_read(struct tdb_context *tdb, tdb_off_t off,
        enum TDB_ERROR ecode;
 
        /* break it down into block sized ops */
-       while (len + (off % getpagesize()) > getpagesize()) {
-               tdb_len_t len2 = getpagesize() - (off % getpagesize());
+       while (len + (off % PAGESIZE) > PAGESIZE) {
+               tdb_len_t len2 = PAGESIZE - (off % PAGESIZE);
                ecode = transaction_read(tdb, off, buf, len2);
                if (ecode != TDB_SUCCESS) {
                        return ecode;
@@ -147,7 +148,7 @@ static enum TDB_ERROR transaction_read(struct tdb_context *tdb, tdb_off_t off,
                return TDB_SUCCESS;
        }
 
-       blk = off / getpagesize();
+       blk = off / PAGESIZE;
 
        /* see if we have it in the block list */
        if (tdb->transaction->num_blocks <= blk ||
@@ -169,7 +170,7 @@ static enum TDB_ERROR transaction_read(struct tdb_context *tdb, tdb_off_t off,
        }
 
        /* now copy it out of this block */
-       memcpy(buf, tdb->transaction->blocks[blk] + (off % getpagesize()), len);
+       memcpy(buf, tdb->transaction->blocks[blk] + (off % PAGESIZE), len);
        return TDB_SUCCESS;
 
 fail:
@@ -198,8 +199,8 @@ static enum TDB_ERROR transaction_write(struct tdb_context *tdb, tdb_off_t off,
        }
 
        /* break it up into block sized chunks */
-       while (len + (off % getpagesize()) > getpagesize()) {
-               tdb_len_t len2 = getpagesize() - (off % getpagesize());
+       while (len + (off % PAGESIZE) > PAGESIZE) {
+               tdb_len_t len2 = PAGESIZE - (off % PAGESIZE);
                ecode = transaction_write(tdb, off, buf, len2);
                if (ecode != TDB_SUCCESS) {
                        return -1;
@@ -215,8 +216,8 @@ static enum TDB_ERROR transaction_write(struct tdb_context *tdb, tdb_off_t off,
                return TDB_SUCCESS;
        }
 
-       blk = off / getpagesize();
-       off = off % getpagesize();
+       blk = off / PAGESIZE;
+       off = off % PAGESIZE;
 
        if (tdb->transaction->num_blocks <= blk) {
                uint8_t **new_blocks;
@@ -244,20 +245,20 @@ static enum TDB_ERROR transaction_write(struct tdb_context *tdb, tdb_off_t off,
 
        /* allocate and fill a block? */
        if (tdb->transaction->blocks[blk] == NULL) {
-               tdb->transaction->blocks[blk] = (uint8_t *)calloc(getpagesize(), 1);
+               tdb->transaction->blocks[blk] = (uint8_t *)calloc(PAGESIZE, 1);
                if (tdb->transaction->blocks[blk] == NULL) {
                        ecode = tdb_logerr(tdb, TDB_ERR_OOM, TDB_LOG_ERROR,
                                           "transaction_write:"
                                           " failed to allocate");
                        goto fail;
                }
-               if (tdb->transaction->old_map_size > blk * getpagesize()) {
-                       tdb_len_t len2 = getpagesize();
-                       if (len2 + (blk * getpagesize()) > tdb->transaction->old_map_size) {
-                               len2 = tdb->transaction->old_map_size - (blk * getpagesize());
+               if (tdb->transaction->old_map_size > blk * PAGESIZE) {
+                       tdb_len_t len2 = PAGESIZE;
+                       if (len2 + (blk * PAGESIZE) > tdb->transaction->old_map_size) {
+                               len2 = tdb->transaction->old_map_size - (blk * PAGESIZE);
                        }
                        ecode = tdb->transaction->io_methods->tread(tdb,
-                                       blk * getpagesize(),
+                                       blk * PAGESIZE,
                                        tdb->transaction->blocks[blk],
                                        len2);
                        if (ecode != TDB_SUCCESS) {
@@ -306,8 +307,8 @@ static void transaction_write_existing(struct tdb_context *tdb, tdb_off_t off,
        size_t blk;
 
        /* break it up into block sized chunks */
-       while (len + (off % getpagesize()) > getpagesize()) {
-               tdb_len_t len2 = getpagesize() - (off % getpagesize());
+       while (len + (off % PAGESIZE) > PAGESIZE) {
+               tdb_len_t len2 = PAGESIZE - (off % PAGESIZE);
                transaction_write_existing(tdb, off, buf, len2);
                len -= len2;
                off += len2;
@@ -320,8 +321,8 @@ static void transaction_write_existing(struct tdb_context *tdb, tdb_off_t off,
                return;
        }
 
-       blk = off / getpagesize();
-       off = off % getpagesize();
+       blk = off / PAGESIZE;
+       off = off % PAGESIZE;
 
        if (tdb->transaction->num_blocks <= blk ||
            tdb->transaction->blocks[blk] == NULL) {
@@ -379,10 +380,10 @@ static enum TDB_ERROR transaction_expand_file(struct tdb_context *tdb,
 static void *transaction_direct(struct tdb_context *tdb, tdb_off_t off,
                                size_t len, bool write_mode)
 {
-       size_t blk = off / getpagesize(), end_blk;
+       size_t blk = off / PAGESIZE, end_blk;
 
        /* This is wrong for zero-length blocks, but will fail gracefully */
-       end_blk = (off + len - 1) / getpagesize();
+       end_blk = (off + len - 1) / PAGESIZE;
 
        /* Can only do direct if in single block and we've already copied. */
        if (write_mode) {
@@ -392,17 +393,17 @@ static void *transaction_direct(struct tdb_context *tdb, tdb_off_t off,
                        return NULL;
                if (tdb->transaction->blocks[blk] == NULL)
                        return NULL;
-               return tdb->transaction->blocks[blk] + off % getpagesize();
+               return tdb->transaction->blocks[blk] + off % PAGESIZE;
        }
 
        /* Single which we have copied? */
        if (blk == end_blk
            && blk < tdb->transaction->num_blocks
            && tdb->transaction->blocks[blk])
-               return tdb->transaction->blocks[blk] + off % getpagesize();
+               return tdb->transaction->blocks[blk] + off % PAGESIZE;
 
        /* Otherwise must be all not copied. */
-       while (blk < end_blk) {
+       while (blk <= end_blk) {
                if (blk >= tdb->transaction->num_blocks)
                        break;
                if (tdb->transaction->blocks[blk])
@@ -437,7 +438,7 @@ static enum TDB_ERROR transaction_sync(struct tdb_context *tdb,
        }
 #ifdef MS_SYNC
        if (tdb->file->map_ptr) {
-               tdb_off_t moffset = offset & ~(getpagesize()-1);
+               tdb_off_t moffset = offset & ~(PAGESIZE-1);
                if (msync(moffset + (char *)tdb->file->map_ptr,
                          length + (offset - moffset), MS_SYNC) != 0) {
                        return tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
@@ -519,32 +520,46 @@ enum TDB_ERROR tdb_transaction_start(struct tdb_context *tdb)
 
        /* some sanity checks */
        if (tdb->read_only || (tdb->flags & TDB_INTERNAL)) {
-               return tdb_logerr(tdb, TDB_ERR_EINVAL, TDB_LOG_USE_ERROR,
-                                 "tdb_transaction_start: cannot start a"
-                                 " transaction on a read-only or internal db");
+               return tdb->last_error = tdb_logerr(tdb, TDB_ERR_EINVAL,
+                                                   TDB_LOG_USE_ERROR,
+                                                   "tdb_transaction_start:"
+                                                   " cannot start a"
+                                                   " transaction on a "
+                                                   "read-only or internal db");
        }
 
        /* cope with nested tdb_transaction_start() calls */
        if (tdb->transaction != NULL) {
-               return tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_USE_ERROR,
-                                 "tdb_transaction_start:"
-                                 " already inside transaction");
+               if (!(tdb->flags & TDB_ALLOW_NESTING)) {
+                       return tdb->last_error
+                               = tdb_logerr(tdb, TDB_ERR_IO,
+                                            TDB_LOG_USE_ERROR,
+                                            "tdb_transaction_start:"
+                                            " already inside transaction");
+               }
+               tdb->transaction->nesting++;
+               return 0;
        }
 
        if (tdb_has_hash_locks(tdb)) {
                /* the caller must not have any locks when starting a
                   transaction as otherwise we'll be screwed by lack
                   of nested locks in POSIX */
-               return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
-                                 "tdb_transaction_start: cannot start a"
-                                 " transaction with locks held");
+               return tdb->last_error = tdb_logerr(tdb, TDB_ERR_LOCK,
+                                                   TDB_LOG_USE_ERROR,
+                                                   "tdb_transaction_start:"
+                                                   " cannot start a"
+                                                   " transaction with locks"
+                                                   " held");
        }
 
        tdb->transaction = (struct tdb_transaction *)
                calloc(sizeof(struct tdb_transaction), 1);
        if (tdb->transaction == NULL) {
-               return tdb_logerr(tdb, TDB_ERR_OOM, TDB_LOG_ERROR,
-                                 "tdb_transaction_start: cannot allocate");
+               return tdb->last_error = tdb_logerr(tdb, TDB_ERR_OOM,
+                                                   TDB_LOG_ERROR,
+                                                   "tdb_transaction_start:"
+                                                   " cannot allocate");
        }
 
        /* get the transaction write lock. This is a blocking lock. As
@@ -554,7 +569,7 @@ enum TDB_ERROR tdb_transaction_start(struct tdb_context *tdb)
        if (ecode != TDB_SUCCESS) {
                SAFE_FREE(tdb->transaction->blocks);
                SAFE_FREE(tdb->transaction);
-               return ecode;
+               return tdb->last_error = ecode;
        }
 
        /* get a read lock over entire file. This is upgraded to a write
@@ -573,13 +588,13 @@ enum TDB_ERROR tdb_transaction_start(struct tdb_context *tdb)
           transaction specific methods */
        tdb->transaction->io_methods = tdb->methods;
        tdb->methods = &transaction_methods;
-       return TDB_SUCCESS;
+       return tdb->last_error = TDB_SUCCESS;
 
 fail_allrecord_lock:
        tdb_transaction_unlock(tdb, F_WRLCK);
        SAFE_FREE(tdb->transaction->blocks);
        SAFE_FREE(tdb->transaction);
-       return ecode;
+       return tdb->last_error = ecode;
 }
 
 
@@ -592,16 +607,16 @@ void tdb_transaction_cancel(struct tdb_context *tdb)
 }
 
 /*
-  work out how much space the linearised recovery data will consume
+  work out how much space the linearised recovery data will consume (worst case)
 */
 static tdb_len_t tdb_recovery_size(struct tdb_context *tdb)
 {
        tdb_len_t recovery_size = 0;
        int i;
 
-       recovery_size = sizeof(tdb_len_t);
+       recovery_size = 0;
        for (i=0;i<tdb->transaction->num_blocks;i++) {
-               if (i * getpagesize() >= tdb->transaction->old_map_size) {
+               if (i * PAGESIZE >= tdb->transaction->old_map_size) {
                        break;
                }
                if (tdb->transaction->blocks[i] == NULL) {
@@ -611,93 +626,203 @@ static tdb_len_t tdb_recovery_size(struct tdb_context *tdb)
                if (i == tdb->transaction->num_blocks-1) {
                        recovery_size += tdb->transaction->last_block_size;
                } else {
-                       recovery_size += getpagesize();
+                       recovery_size += PAGESIZE;
                }
        }
 
        return recovery_size;
 }
 
-/*
-  allocate the recovery area, or use an existing recovery area if it is
-  large enough
-*/
-static enum TDB_ERROR tdb_recovery_allocate(struct tdb_context *tdb,
-                                           tdb_len_t *recovery_size,
-                                           tdb_off_t *recovery_offset,
-                                           tdb_len_t *recovery_max_size)
+static enum TDB_ERROR tdb_recovery_area(struct tdb_context *tdb,
+                                       const struct tdb_methods *methods,
+                                       tdb_off_t *recovery_offset,
+                                       struct tdb_recovery_record *rec)
 {
-       struct tdb_recovery_record rec;
-       const struct tdb_methods *methods = tdb->transaction->io_methods;
-       tdb_off_t recovery_head;
-       size_t addition;
        enum TDB_ERROR ecode;
 
-       recovery_head = tdb_read_off(tdb, offsetof(struct tdb_header,recovery));
-       if (TDB_OFF_IS_ERR(recovery_head)) {
-               return tdb_logerr(tdb, recovery_head, TDB_LOG_ERROR,
-                                 "tdb_recovery_allocate:"
-                                 " failed to read recovery head");
+       *recovery_offset = tdb_read_off(tdb,
+                                       offsetof(struct tdb_header, recovery));
+       if (TDB_OFF_IS_ERR(*recovery_offset)) {
+               return *recovery_offset;
        }
 
-       if (recovery_head != 0) {
-               ecode = methods->tread(tdb, recovery_head, &rec, sizeof(rec));
-               if (ecode != TDB_SUCCESS) {
-                       return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
-                                         "tdb_recovery_allocate:"
-                                         " failed to read recovery record");
-               }
-               tdb_convert(tdb, &rec, sizeof(rec));
-               /* ignore invalid recovery regions: can happen in crash */
-               if (rec.magic != TDB_RECOVERY_MAGIC &&
-                   rec.magic != TDB_RECOVERY_INVALID_MAGIC) {
-                       recovery_head = 0;
+       if (*recovery_offset == 0) {
+               rec->max_len = 0;
+               return TDB_SUCCESS;
+       }
+
+       ecode = methods->tread(tdb, *recovery_offset, rec, sizeof(*rec));
+       if (ecode != TDB_SUCCESS)
+               return ecode;
+
+       tdb_convert(tdb, rec, sizeof(*rec));
+       /* ignore invalid recovery regions: can happen in crash */
+       if (rec->magic != TDB_RECOVERY_MAGIC &&
+           rec->magic != TDB_RECOVERY_INVALID_MAGIC) {
+               *recovery_offset = 0;
+               rec->max_len = 0;
+       }
+       return TDB_SUCCESS;
+}
+
+static unsigned int same(const unsigned char *new,
+                        const unsigned char *old,
+                        unsigned int length)
+{
+       unsigned int i;
+
+       for (i = 0; i < length; i++) {
+               if (new[i] != old[i])
+                       break;
+       }
+       return i;
+}
+
+static unsigned int different(const unsigned char *new,
+                             const unsigned char *old,
+                             unsigned int length,
+                             unsigned int min_same,
+                             unsigned int *samelen)
+{
+       unsigned int i;
+
+       *samelen = 0;
+       for (i = 0; i < length; i++) {
+               if (new[i] == old[i]) {
+                       (*samelen)++;
+               } else {
+                       if (*samelen >= min_same) {
+                               return i - *samelen;
+                       }
+                       *samelen = 0;
                }
        }
 
-       *recovery_size = tdb_recovery_size(tdb);
+       if (*samelen < min_same)
+               *samelen = 0;
+       return length - *samelen;
+}
+
+/* Allocates recovery blob, without tdb_recovery_record at head set up. */
+static struct tdb_recovery_record *alloc_recovery(struct tdb_context *tdb,
+                                                 tdb_len_t *len)
+{
+       struct tdb_recovery_record *rec;
+       size_t i;
+       enum TDB_ERROR ecode;
+       unsigned char *p;
+       const struct tdb_methods *old_methods = tdb->methods;
 
-       if (recovery_head != 0 && *recovery_size <= rec.max_len) {
-               /* it fits in the existing area */
-               *recovery_max_size = rec.max_len;
-               *recovery_offset = recovery_head;
-               return TDB_SUCCESS;
+       rec = malloc(sizeof(*rec) + tdb_recovery_size(tdb));
+       if (!rec) {
+               tdb_logerr(tdb, TDB_ERR_OOM, TDB_LOG_ERROR,
+                          "transaction_setup_recovery:"
+                          " cannot allocate");
+               return TDB_ERR_PTR(TDB_ERR_OOM);
        }
 
-       /* we need to free up the old recovery area, then allocate a
-          new one at the end of the file. Note that we cannot use
-          normal allocation to allocate the new one as that might return
-          us an area that is being currently used (as of the start of
-          the transaction) */
-       if (recovery_head != 0) {
-               add_stat(tdb, frees, 1);
-               ecode = add_free_record(tdb, recovery_head,
-                                       sizeof(rec) + rec.max_len);
-               if (ecode != TDB_SUCCESS) {
-                       return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
-                                         "tdb_recovery_allocate:"
-                                         " failed to free previous"
-                                         " recovery area");
+       /* We temporarily revert to the old I/O methods, so we can use
+        * tdb_access_read */
+       tdb->methods = tdb->transaction->io_methods;
+
+       /* build the recovery data into a single blob to allow us to do a single
+          large write, which should be more efficient */
+       p = (unsigned char *)(rec + 1);
+       for (i=0;i<tdb->transaction->num_blocks;i++) {
+               tdb_off_t offset;
+               tdb_len_t length;
+               unsigned int off;
+               const unsigned char *buffer;
+
+               if (tdb->transaction->blocks[i] == NULL) {
+                       continue;
+               }
+
+               offset = i * PAGESIZE;
+               length = PAGESIZE;
+               if (i == tdb->transaction->num_blocks-1) {
+                       length = tdb->transaction->last_block_size;
+               }
+
+               if (offset >= tdb->transaction->old_map_size) {
+                       continue;
+               }
+
+               if (offset + length > tdb->file->map_size) {
+                       ecode = tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
+                                          "tdb_transaction_setup_recovery:"
+                                          " transaction data over new region"
+                                          " boundary");
+                       goto fail;
                }
+               if (offset + length > tdb->transaction->old_map_size) {
+                       /* Short read at EOF. */
+                       length = tdb->transaction->old_map_size - offset;
+               }
+               buffer = tdb_access_read(tdb, offset, length, false);
+               if (TDB_PTR_IS_ERR(buffer)) {
+                       ecode = TDB_PTR_ERR(buffer);
+                       goto fail;
+               }
+
+               /* Skip over anything the same at the start. */
+               off = same(tdb->transaction->blocks[i], buffer, length);
+               offset += off;
+
+               while (off < length) {
+                       tdb_len_t len;
+                       unsigned int samelen;
+
+                       len = different(tdb->transaction->blocks[i] + off,
+                                       buffer + off, length - off,
+                                       sizeof(offset) + sizeof(len) + 1,
+                                       &samelen);
+
+                       memcpy(p, &offset, sizeof(offset));
+                       memcpy(p + sizeof(offset), &len, sizeof(len));
+                       tdb_convert(tdb, p, sizeof(offset) + sizeof(len));
+                       p += sizeof(offset) + sizeof(len);
+                       memcpy(p, buffer + off, len);
+                       p += len;
+                       off += len + samelen;
+                       offset += len + samelen;
+               }
+               tdb_access_release(tdb, buffer);
        }
 
-       /* the tdb_free() call might have increased the recovery size */
-       *recovery_size = tdb_recovery_size(tdb);
+       *len = p - (unsigned char *)(rec + 1);
+       tdb->methods = old_methods;
+       return rec;
+
+fail:
+       free(rec);
+       tdb->methods = old_methods;
+       return TDB_ERR_PTR(ecode);
+}
+
+static tdb_off_t create_recovery_area(struct tdb_context *tdb,
+                                     tdb_len_t rec_length,
+                                     struct tdb_recovery_record *rec)
+{
+       tdb_off_t off, recovery_off;
+       tdb_len_t addition;
+       enum TDB_ERROR ecode;
+       const struct tdb_methods *methods = tdb->transaction->io_methods;
 
-       /* round up to a multiple of page size */
-       *recovery_max_size
-               = (((sizeof(rec) + *recovery_size) + getpagesize()-1)
-                  & ~(getpagesize()-1))
-               - sizeof(rec);
-       *recovery_offset = tdb->file->map_size;
-       recovery_head = *recovery_offset;
+       /* round up to a multiple of page size. Overallocate, since each
+        * such allocation forces us to expand the file. */
+       rec->max_len
+               = (((sizeof(*rec) + rec_length + rec_length / 2)
+                   + PAGESIZE-1) & ~(PAGESIZE-1))
+               - sizeof(*rec);
+       off = tdb->file->map_size;
 
        /* Restore ->map_size before calling underlying expand_file.
           Also so that we don't try to expand the file again in the
           transaction commit, which would destroy the recovery
           area */
        addition = (tdb->file->map_size - tdb->transaction->old_map_size) +
-               sizeof(rec) + *recovery_max_size;
+               sizeof(*rec) + rec->max_len;
        tdb->file->map_size = tdb->transaction->old_map_size;
        ecode = methods->expand_file(tdb, addition);
        if (ecode != TDB_SUCCESS) {
@@ -713,159 +838,118 @@ static enum TDB_ERROR tdb_recovery_allocate(struct tdb_context *tdb,
 
        /* write the recovery header offset and sync - we can sync without a race here
           as the magic ptr in the recovery record has not been set */
-       tdb_convert(tdb, &recovery_head, sizeof(recovery_head));
+       recovery_off = off;
+       tdb_convert(tdb, &recovery_off, sizeof(recovery_off));
        ecode = methods->twrite(tdb, offsetof(struct tdb_header, recovery),
-                               &recovery_head, sizeof(tdb_off_t));
+                               &recovery_off, sizeof(tdb_off_t));
        if (ecode != TDB_SUCCESS) {
                return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
                                  "tdb_recovery_allocate:"
                                  " failed to write recovery head");
        }
        transaction_write_existing(tdb, offsetof(struct tdb_header, recovery),
-                                  &recovery_head,
+                                  &recovery_off,
                                   sizeof(tdb_off_t));
-       return TDB_SUCCESS;
-}
-
-/* Set up header for the recovery record. */
-static void set_recovery_header(struct tdb_recovery_record *rec,
-                               uint64_t magic,
-                               uint64_t datalen, uint64_t actuallen,
-                               uint64_t oldsize)
-{
-       rec->magic = magic;
-       rec->max_len = actuallen;
-       rec->len = datalen;
-       rec->eof = oldsize;
+       return off;
 }
 
 /*
   setup the recovery data that will be used on a crash during commit
 */
-static enum TDB_ERROR transaction_setup_recovery(struct tdb_context *tdb,
-                                                tdb_off_t *magic_offset)
+static enum TDB_ERROR transaction_setup_recovery(struct tdb_context *tdb)
 {
-       /* Initialized for GCC's 4.4.5 overzealous uninitialized warnings. */
        tdb_len_t recovery_size = 0;
-       tdb_off_t recovery_offset = 0, recovery_max_size = 0;
-       unsigned char *data, *p;
-       const struct tdb_methods *methods = tdb->transaction->io_methods;
-       struct tdb_recovery_record *rec;
+       tdb_off_t recovery_off = 0;
        tdb_off_t old_map_size = tdb->transaction->old_map_size;
-       uint64_t magic, tailer;
-       int i;
+       struct tdb_recovery_record *recovery;
+       const struct tdb_methods *methods = tdb->transaction->io_methods;
+       uint64_t magic;
        enum TDB_ERROR ecode;
 
-       /*
-         check that the recovery area has enough space
-       */
-       ecode = tdb_recovery_allocate(tdb, &recovery_size,
-                                     &recovery_offset, &recovery_max_size);
-       if (ecode != TDB_SUCCESS) {
-               return ecode;
-       }
+       recovery = alloc_recovery(tdb, &recovery_size);
+       if (TDB_PTR_IS_ERR(recovery))
+               return TDB_PTR_ERR(recovery);
 
-       data = (unsigned char *)malloc(recovery_size + sizeof(*rec));
-       if (data == NULL) {
-               return tdb_logerr(tdb, TDB_ERR_OOM, TDB_LOG_ERROR,
-                                 "transaction_setup_recovery:"
-                                 " cannot allocate");
+       ecode = tdb_recovery_area(tdb, methods, &recovery_off, recovery);
+       if (ecode) {
+               free(recovery);
+               return ecode;
        }
 
-       rec = (struct tdb_recovery_record *)data;
-       set_recovery_header(rec, TDB_RECOVERY_INVALID_MAGIC,
-                           recovery_size, recovery_max_size, old_map_size);
-       tdb_convert(tdb, rec, sizeof(*rec));
-
-       /* build the recovery data into a single blob to allow us to do a single
-          large write, which should be more efficient */
-       p = data + sizeof(*rec);
-       for (i=0;i<tdb->transaction->num_blocks;i++) {
-               tdb_off_t offset;
-               tdb_len_t length;
-
-               if (tdb->transaction->blocks[i] == NULL) {
-                       continue;
-               }
+       if (recovery->max_len < recovery_size) {
+               /* Not large enough. Free up old recovery area. */
+               if (recovery_off) {
+                       tdb->stats.frees++;
+                       ecode = add_free_record(tdb, recovery_off,
+                                               sizeof(*recovery)
+                                               + recovery->max_len,
+                                               TDB_LOCK_WAIT, true);
+                       free(recovery);
+                       if (ecode != TDB_SUCCESS) {
+                               return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
+                                                 "tdb_recovery_allocate:"
+                                                 " failed to free previous"
+                                                 " recovery area");
+                       }
 
-               offset = i * getpagesize();
-               length = getpagesize();
-               if (i == tdb->transaction->num_blocks-1) {
-                       length = tdb->transaction->last_block_size;
+                       /* Refresh recovery after add_free_record above. */
+                       recovery = alloc_recovery(tdb, &recovery_size);
+                       if (TDB_PTR_IS_ERR(recovery))
+                               return TDB_PTR_ERR(recovery);
                }
 
-               if (offset >= old_map_size) {
-                       continue;
-               }
-               if (offset + length > tdb->file->map_size) {
-                       free(data);
-                       return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
-                                         "tdb_transaction_setup_recovery:"
-                                         " transaction data over new region"
-                                         " boundary");
-               }
-               memcpy(p, &offset, sizeof(offset));
-               memcpy(p + sizeof(offset), &length, sizeof(length));
-               tdb_convert(tdb, p, sizeof(offset) + sizeof(length));
-
-               /* the recovery area contains the old data, not the
-                  new data, so we have to call the original tdb_read
-                  method to get it */
-               ecode = methods->tread(tdb, offset,
-                                      p + sizeof(offset) + sizeof(length),
-                                      length);
-               if (ecode != TDB_SUCCESS) {
-                       free(data);
-                       return ecode;
+               recovery_off = create_recovery_area(tdb, recovery_size,
+                                                   recovery);
+               if (TDB_OFF_IS_ERR(recovery_off)) {
+                       free(recovery);
+                       return recovery_off;
                }
-               p += sizeof(offset) + sizeof(length) + length;
        }
 
-       /* and the tailer */
-       tailer = sizeof(*rec) + recovery_max_size;
-       memcpy(p, &tailer, sizeof(tailer));
-       tdb_convert(tdb, p, sizeof(tailer));
+       /* Now we know size, convert rec header. */
+       recovery->magic = TDB_RECOVERY_INVALID_MAGIC;
+       recovery->len = recovery_size;
+       recovery->eof = old_map_size;
+       tdb_convert(tdb, recovery, sizeof(*recovery));
 
        /* write the recovery data to the recovery area */
-       ecode = methods->twrite(tdb, recovery_offset, data,
-                               sizeof(*rec) + recovery_size);
+       ecode = methods->twrite(tdb, recovery_off, recovery, recovery_size);
        if (ecode != TDB_SUCCESS) {
-               free(data);
+               free(recovery);
                return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
                                  "tdb_transaction_setup_recovery:"
                                  " failed to write recovery data");
        }
-       transaction_write_existing(tdb, recovery_offset, data,
-                                  sizeof(*rec) + recovery_size);
+       transaction_write_existing(tdb, recovery_off, recovery, recovery_size);
+
+       free(recovery);
 
        /* as we don't have ordered writes, we have to sync the recovery
           data before we update the magic to indicate that the recovery
           data is present */
-       ecode = transaction_sync(tdb, recovery_offset,
-                                sizeof(*rec) + recovery_size);
-       if (ecode != TDB_SUCCESS) {
-               free(data);
+       ecode = transaction_sync(tdb, recovery_off, recovery_size);
+       if (ecode != TDB_SUCCESS)
                return ecode;
-       }
-
-       free(data);
 
        magic = TDB_RECOVERY_MAGIC;
        tdb_convert(tdb, &magic, sizeof(magic));
 
-       *magic_offset = recovery_offset + offsetof(struct tdb_recovery_record,
-                                                  magic);
+       tdb->transaction->magic_offset
+               = recovery_off + offsetof(struct tdb_recovery_record, magic);
 
-       ecode = methods->twrite(tdb, *magic_offset, &magic, sizeof(magic));
+       ecode = methods->twrite(tdb, tdb->transaction->magic_offset,
+                               &magic, sizeof(magic));
        if (ecode != TDB_SUCCESS) {
                return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
                                  "tdb_transaction_setup_recovery:"
                                  " failed to write recovery magic");
        }
-       transaction_write_existing(tdb, *magic_offset, &magic, sizeof(magic));
+       transaction_write_existing(tdb, tdb->transaction->magic_offset,
+                                  &magic, sizeof(magic));
 
        /* ensure the recovery magic marker is on disk */
-       return transaction_sync(tdb, *magic_offset, sizeof(magic));
+       return transaction_sync(tdb, tdb->transaction->magic_offset,
+                               sizeof(magic));
 }
 
 static enum TDB_ERROR _tdb_transaction_prepare_commit(struct tdb_context *tdb)
@@ -895,7 +979,6 @@ static enum TDB_ERROR _tdb_transaction_prepare_commit(struct tdb_context *tdb)
 
 
        if (tdb->transaction->nesting != 0) {
-               tdb->transaction->nesting--;
                return TDB_SUCCESS;
        }
 
@@ -909,10 +992,6 @@ static enum TDB_ERROR _tdb_transaction_prepare_commit(struct tdb_context *tdb)
        /* upgrade the main transaction lock region to a write lock */
        ecode = tdb_allrecord_upgrade(tdb);
        if (ecode != TDB_SUCCESS) {
-               tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
-                        "tdb_transaction_prepare_commit:"
-                        " failed to upgrade hash locks");
-               _tdb_transaction_cancel(tdb);
                return ecode;
        }
 
@@ -920,24 +999,15 @@ static enum TDB_ERROR _tdb_transaction_prepare_commit(struct tdb_context *tdb)
           during the commit */
        ecode = tdb_lock_open(tdb, TDB_LOCK_WAIT|TDB_LOCK_NOCHECK);
        if (ecode != TDB_SUCCESS) {
-               tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
-                          "tdb_transaction_prepare_commit:"
-                          " failed to get open lock");
-               _tdb_transaction_cancel(tdb);
                return ecode;
        }
 
        /* Since we have whole db locked, we don't need the expansion lock. */
        if (!(tdb->flags & TDB_NOSYNC)) {
-               /* write the recovery data to the end of the file */
-               ecode = transaction_setup_recovery(tdb,
-                                                  &tdb->transaction
-                                                  ->magic_offset);
+               /* Sets up tdb->transaction->recovery and
+                * tdb->transaction->magic_offset. */
+               ecode = transaction_setup_recovery(tdb);
                if (ecode != TDB_SUCCESS) {
-                       tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
-                                "tdb_transaction_prepare_commit:"
-                                " failed to setup recovery data");
-                       _tdb_transaction_cancel(tdb);
                        return ecode;
                }
        }
@@ -953,10 +1023,6 @@ static enum TDB_ERROR _tdb_transaction_prepare_commit(struct tdb_context *tdb)
                tdb->file->map_size = tdb->transaction->old_map_size;
                ecode = methods->expand_file(tdb, add);
                if (ecode != TDB_SUCCESS) {
-                       tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
-                                "tdb_transaction_prepare_commit:"
-                                " expansion failed");
-                       _tdb_transaction_cancel(tdb);
                        return ecode;
                }
        }
@@ -983,27 +1049,31 @@ enum TDB_ERROR tdb_transaction_commit(struct tdb_context *tdb)
        enum TDB_ERROR ecode;
 
        if (tdb->transaction == NULL) {
-               return tdb_logerr(tdb, TDB_ERR_EINVAL, TDB_LOG_USE_ERROR,
-                                 "tdb_transaction_commit: no transaction");
+               return tdb->last_error = tdb_logerr(tdb, TDB_ERR_EINVAL,
+                                                   TDB_LOG_USE_ERROR,
+                                                   "tdb_transaction_commit:"
+                                                   " no transaction");
        }
 
        tdb_trace(tdb, "tdb_transaction_commit");
 
        if (tdb->transaction->nesting != 0) {
                tdb->transaction->nesting--;
-               return TDB_SUCCESS;
+               return tdb->last_error = TDB_SUCCESS;
        }
 
        /* check for a null transaction */
        if (tdb->transaction->blocks == NULL) {
                _tdb_transaction_cancel(tdb);
-               return TDB_SUCCESS;
+               return tdb->last_error = TDB_SUCCESS;
        }
 
        if (!tdb->transaction->prepared) {
                ecode = _tdb_transaction_prepare_commit(tdb);
-               if (ecode != TDB_SUCCESS)
-                       return ecode;
+               if (ecode != TDB_SUCCESS) {
+                       _tdb_transaction_cancel(tdb);
+                       return tdb->last_error = ecode;
+               }
        }
 
        methods = tdb->transaction->io_methods;
@@ -1017,8 +1087,8 @@ enum TDB_ERROR tdb_transaction_commit(struct tdb_context *tdb)
                        continue;
                }
 
-               offset = i * getpagesize();
-               length = getpagesize();
+               offset = i * PAGESIZE;
+               length = PAGESIZE;
                if (i == tdb->transaction->num_blocks-1) {
                        length = tdb->transaction->last_block_size;
                }
@@ -1026,10 +1096,6 @@ enum TDB_ERROR tdb_transaction_commit(struct tdb_context *tdb)
                ecode = methods->twrite(tdb, offset,
                                        tdb->transaction->blocks[i], length);
                if (ecode != TDB_SUCCESS) {
-                       tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
-                                  "tdb_transaction_commit:"
-                                  " write failed during commit");
-
                        /* we've overwritten part of the data and
                           possibly expanded the file, so we need to
                           run the crash recovery code */
@@ -1038,7 +1104,7 @@ enum TDB_ERROR tdb_transaction_commit(struct tdb_context *tdb)
 
                        _tdb_transaction_cancel(tdb);
 
-                       return ecode;
+                       return tdb->last_error = ecode;
                }
                SAFE_FREE(tdb->transaction->blocks[i]);
        }
@@ -1049,7 +1115,7 @@ enum TDB_ERROR tdb_transaction_commit(struct tdb_context *tdb)
        /* ensure the new data is on disk */
        ecode = transaction_sync(tdb, 0, tdb->file->map_size);
        if (ecode != TDB_SUCCESS) {
-               return ecode;
+               return tdb->last_error = ecode;
        }
 
        /*
@@ -1068,10 +1134,11 @@ enum TDB_ERROR tdb_transaction_commit(struct tdb_context *tdb)
 #endif
 
        /* use a transaction cancel to free memory and remove the
-          transaction locks */
+          transaction locks: it "restores" map_size, too. */
+       tdb->transaction->old_map_size = tdb->file->map_size;
        _tdb_transaction_cancel(tdb);
 
-       return TDB_SUCCESS;
+       return tdb->last_error = TDB_SUCCESS;
 }