libsqfs: block processor: backport exact fragment matching

This commit is an amalgamation of the commits on master that
implement exact matching of fragment blocks during deduplication.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

8 files changed, 379 insertions, 66 deletions

diff --git a/include/hash_table.h b/include/hash_table.h
index 6f377c9..813e059 100644
--- a/include/hash_table.h
+++ b/include/hash_table.h
@@ -42,9 +42,10 @@ struct hash_entry {
 
 struct hash_table {
    struct hash_entry *table;
-   sqfs_u32 (*key_hash_function)(const void *key);
-   bool (*key_equals_function)(const void *a, const void *b);
+   sqfs_u32 (*key_hash_function)(void *user, const void *key);
+   bool (*key_equals_function)(void *user, const void *a, const void *b);
    const void *deleted_key;
+   void *user;
    sqfs_u32 size;
    sqfs_u32 rehash;
    sqfs_u64 size_magic;
@@ -56,8 +57,8 @@ struct hash_table {
 };
 
 SQFS_INTERNAL struct hash_table *
-hash_table_create(sqfs_u32 (*key_hash_function)(const void *key),
-                  bool (*key_equals_function)(const void *a,
+hash_table_create(sqfs_u32 (*key_hash_function)(void *user, const void *key),
+                  bool (*key_equals_function)(void *user, const void *a,
                                               const void *b));
 
 SQFS_INTERNAL struct hash_table *
diff --git a/include/sqfs/block_processor.h b/include/sqfs/block_processor.h
index 1846069..a5eed33 100644
--- a/include/sqfs/block_processor.h
+++ b/include/sqfs/block_processor.h
@@ -110,12 +110,90 @@ struct sqfs_block_processor_stats_t {
 	sqfs_u64 actual_frag_count;
 };
 
+/**
+ * @struct sqfs_block_processor_desc_t
+ *
+ * @brief Encapsulates a description for an @ref sqfs_block_processor_t
+ *
+ * An instance of this struct is used by @ref sqfs_block_processor_create_ex to
+ * instantiate block processor objects.
+ */
+struct sqfs_block_processor_desc_t {
+	/**
+	 * @brief Holds the size of the structure.
+	 *
+	 * If a later version of libsquashfs expands this structure, the value
+	 * of this field can be used to check at runtime whether the newer
+	 * fields are avaialable or not.
+	 *
+	 * If @ref sqfs_block_processor_create_ex is given a struct whose size
+	 * it does not recognize, it returns @ref SQFS_ERROR_ARG_INVALID.
+	 */
+	sqfs_u32 size;
+
+	/**
+	 * @brief The maximum size of a data block.
+	 */
+	sqfs_u32 max_block_size;
+
+	/**
+	 * @brief The number of worker threads to create.
+	 */
+	sqfs_u32 num_workers;
+
+	/**
+	 * @brief The maximum number of blocks currently in flight.
+	 *
+	 * When trying to add more, enqueueing blocks until the
+	 * in-flight block count drops below the threshold.
+	 */
+	sqfs_u32 max_backlog;
+
+	/**
+	 * @brief A pointer to a compressor.
+	 *
+	 * If multiple worker threads are used, the deep copy function of the
+	 * compressor is used to create several instances that don't interfere
+	 * with each other. This means, the compressor implementation must be
+	 * able to create copies of itself that can be used independendly and
+	 * concurrently.
+	 */
+	sqfs_compressor_t *cmp;
+
+	/**
+	 * @brief A block writer to send to finished blocks to.
+	 */
+	sqfs_block_writer_t *wr;
+
+	/**
+	 * @brief A fragment table to use for storing block locations.
+	 */
+	sqfs_frag_table_t *tbl;
+
+	/**
+	 * @brief Pointer to a file to read back fragment blocks from.
+	 *
+	 * If file and uncmp are not NULL, the file is used to read back
+	 * fragment blocks during fragment deduplication and verify possible
+	 * matches. If either of them are NULL, the deduplication relies on
+	 * fragment size and hash alone.
+	 */
+	sqfs_file_t *file;
+
+	/**
+	 * @brief A pointer to a compressor the decompresses data.
+	 *
+	 * @copydoc file
+	 */
+	sqfs_compressor_t *uncmp;
+};
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 /**
- * @brief Create a data block writer.
+ * @brief Create a data block processor.
  *
  * @memberof sqfs_block_processor_t
  *
@@ -132,7 +210,7 @@ extern "C" {
  * @param tbl A fragment table to use for storing fragment and fragment block
  *            locations.
  *
- * @return A pointer to a data writer object on success, NULL on allocation
+ * @return A pointer to a block processor object on success, NULL on allocation
  *         failure or on failure to create and initialize the worker threads.
  */
 SQFS_API
@@ -144,6 +222,22 @@ sqfs_block_processor_t *sqfs_block_processor_create(size_t max_block_size,
 						    sqfs_frag_table_t *tbl);
 
 /**
+ * @brief Create a data block processor.
+ *
+ * @memberof sqfs_block_processor_t
+ *
+ * @param desc A pointer to an extensible structure that holds the description
+ *             of the block processor.
+ * @param out On success, returns the pointer to the newly created block
+ *            processor object.
+ *
+ * @return Zero on success, an @ref SQFS_ERROR value on failure.
+ */
+SQFS_API
+int sqfs_block_processor_create_ex(const sqfs_block_processor_desc_t *desc,
+				   sqfs_block_processor_t **out);
+
+/**
  * @brief Start writing a file.
  *
  * @memberof sqfs_block_processor_t
diff --git a/include/sqfs/predef.h b/include/sqfs/predef.h
index e0afac4..55ccc86 100644
--- a/include/sqfs/predef.h
+++ b/include/sqfs/predef.h
@@ -91,6 +91,7 @@ typedef struct sqfs_frag_table_t sqfs_frag_table_t;
 typedef struct sqfs_block_writer_t sqfs_block_writer_t;
 typedef struct sqfs_block_writer_stats_t sqfs_block_writer_stats_t;
 typedef struct sqfs_block_processor_stats_t sqfs_block_processor_stats_t;
+typedef struct sqfs_block_processor_desc_t sqfs_block_processor_desc_t;
 
 typedef struct sqfs_fragment_t sqfs_fragment_t;
 typedef struct sqfs_dir_header_t sqfs_dir_header_t;
diff --git a/lib/sqfs/block_processor/common.c b/lib/sqfs/block_processor/common.c
index b2657e6..d6c0889 100644
--- a/lib/sqfs/block_processor/common.c
+++ b/lib/sqfs/block_processor/common.c
@@ -176,8 +176,11 @@ static int process_completed_fragment(sqfs_block_processor_t *proc,
 		search.hash = frag->checksum;
 		search.size = frag->size;
 
+		proc->frag_cmp_current = frag;
 		entry = hash_table_search_pre_hashed(proc->frag_ht,
 						     search.hash, &search);
+		proc->frag_cmp_current = NULL;
+
 		if (entry != NULL) {
 			if (frag->inode != NULL) {
 				chunk = entry->data;
@@ -238,8 +241,11 @@ static int process_completed_fragment(sqfs_block_processor_t *proc,
 		chunk->size = frag->size;
 		chunk->hash = frag->checksum;
 
+		proc->frag_cmp_current = frag;
 		entry = hash_table_insert_pre_hashed(proc->frag_ht, chunk->hash,
 						     chunk, chunk);
+		proc->frag_cmp_current = NULL;
+
 		if (entry == NULL) {
 			free(chunk);
 			goto fail_outblk;
@@ -261,17 +267,76 @@ fail_outblk:
 	return err;
 }
 
-static uint32_t chunk_info_hash(const void *key)
+static uint32_t chunk_info_hash(void *user, const void *key)
 {
 	const chunk_info_t *chunk = key;
+	(void)user;
 	return chunk->hash;
 }
 
-static bool chunk_info_equals(const void *a, const void *b)
+static bool chunk_info_equals(void *user, const void *k, const void *c)
 {
-	const chunk_info_t *a_ = a, *b_ = b;
-	return a_->size == b_->size &&
-	       a_->hash == b_->hash;
+	const chunk_info_t *key = k, *cmp = c;
+	sqfs_block_processor_t *proc = user;
+	sqfs_fragment_t frag;
+	unsigned char *temp;
+	size_t size;
+	int ret;
+
+	if (key->size != cmp->size || key->hash != cmp->hash)
+		return false;
+
+	if (proc->file == NULL || proc->uncmp == NULL)
+		return true;
+
+	ret = proc->compare_frag_in_flight(proc, proc->frag_cmp_current,
+					   cmp->index, cmp->offset);
+	if (ret == 0)
+		return true;
+
+	if (proc->buffered_index != cmp->index ||
+	    proc->buffered_blk_size == 0) {
+		if (sqfs_frag_table_lookup(proc->frag_tbl, cmp->index, &frag))
+			return false;
+
+		proc->buffered_index = 0xFFFFFFFF;
+		size = SQFS_ON_DISK_BLOCK_SIZE(frag.size);
+
+		if (SQFS_IS_BLOCK_COMPRESSED(frag.size)) {
+			temp = proc->frag_buffer + proc->max_block_size;
+
+			ret = proc->file->read_at(proc->file, frag.start_offset,
+						  temp, size);
+			if (ret != 0)
+				return false;
+
+			ret = proc->uncmp->do_block(proc->uncmp, temp, size,
+						    proc->frag_buffer,
+						    proc->max_block_size);
+			if (ret <= 0)
+				return false;
+
+			size = ret;
+		} else {
+			ret = proc->file->read_at(proc->file, frag.start_offset,
+						  proc->frag_buffer, size);
+			if (ret != 0)
+				return false;
+		}
+
+		proc->buffered_index = cmp->index;
+		proc->buffered_blk_size = size;
+	}
+
+	if (cmp->offset >= proc->buffered_blk_size)
+		return false;
+
+	if (cmp->size > (proc->buffered_blk_size - cmp->offset))
+		return false;
+
+	return memcmp(proc->frag_buffer + cmp->offset,
+		      proc->frag_cmp_current->data,
+		      cmp->size) == 0;
 }
 
 static void ht_delete_function(struct hash_entry *entry)
@@ -287,6 +352,7 @@ void block_processor_cleanup(sqfs_block_processor_t *base)
 		release_old_block(base, base->frag_block);
 
 	free(base->blk_current);
+	free(base->frag_buffer);
 
 	while (base->free_list != NULL) {
 		it = base->free_list;
@@ -297,22 +363,58 @@ void block_processor_cleanup(sqfs_block_processor_t *base)
 	hash_table_destroy(base->frag_ht, ht_delete_function);
 }
 
-int block_processor_init(sqfs_block_processor_t *base, size_t max_block_size,
-			 sqfs_compressor_t *cmp, sqfs_block_writer_t *wr,
-			 sqfs_frag_table_t *tbl)
+int block_processor_init(sqfs_block_processor_t *base,
+			 const sqfs_block_processor_desc_t *desc)
 {
 	base->process_completed_block = process_completed_block;
 	base->process_completed_fragment = process_completed_fragment;
 	base->process_block = process_block;
-	base->max_block_size = max_block_size;
-	base->cmp = cmp;
-	base->frag_tbl = tbl;
-	base->wr = wr;
+	base->max_block_size = desc->max_block_size;
+	base->cmp = desc->cmp;
+	base->frag_tbl = desc->tbl;
+	base->wr = desc->wr;
+	base->file = desc->file;
+	base->uncmp = desc->uncmp;
+	base->buffered_index = 0xFFFFFFFF;
 	base->stats.size = sizeof(base->stats);
 
+	if (desc->file != NULL && desc->uncmp != NULL && desc->tbl != NULL) {
+		base->frag_buffer = malloc(2 * desc->max_block_size);
+		if (base->frag_buffer == NULL)
+			return SQFS_ERROR_ALLOC;
+	}
+
 	base->frag_ht = hash_table_create(chunk_info_hash, chunk_info_equals);
-	if (base->frag_ht == NULL)
-		return -1;
+	if (base->frag_ht == NULL) {
+		free(base->frag_buffer);
+		return SQFS_ERROR_ALLOC;
+	}
 
+	base->frag_ht->user = base;
 	return 0;
 }
+
+sqfs_block_processor_t *sqfs_block_processor_create(size_t max_block_size,
+						    sqfs_compressor_t *cmp,
+						    unsigned int num_workers,
+						    size_t max_backlog,
+						    sqfs_block_writer_t *wr,
+						    sqfs_frag_table_t *tbl)
+{
+	sqfs_block_processor_desc_t desc;
+	sqfs_block_processor_t *out;
+
+	memset(&desc, 0, sizeof(desc));
+	desc.size = sizeof(desc);
+	desc.max_block_size = max_block_size;
+	desc.num_workers = num_workers;
+	desc.max_backlog = max_backlog;
+	desc.cmp = cmp;
+	desc.wr = wr;
+	desc.tbl = tbl;
+
+	if (sqfs_block_processor_create_ex(&desc, &out) != 0)
+		return NULL;
+
+	return out;
+}
diff --git a/lib/sqfs/block_processor/internal.h b/lib/sqfs/block_processor/internal.h
index ee76946..4699dc6 100644
--- a/lib/sqfs/block_processor/internal.h
+++ b/lib/sqfs/block_processor/internal.h
@@ -26,8 +26,7 @@
 #include <stdlib.h>
 #include <assert.h>
 
-typedef struct chunk_info_t {
-	struct chunk_info_t *next;
+typedef struct {
 	sqfs_u32 index;
 	sqfs_u32 offset;
 	sqfs_u32 size;
@@ -82,6 +81,13 @@ struct sqfs_block_processor_t {
 
 	bool begin_called;
 
+	sqfs_file_t *file;
+	sqfs_compressor_t *uncmp;
+	sqfs_block_t *frag_cmp_current;
+	sqfs_u8 *frag_buffer;
+	sqfs_u32 buffered_index;
+	sqfs_u32 buffered_blk_size;
+
 	int (*process_completed_block)(sqfs_block_processor_t *proc,
 				       sqfs_block_t *block);
 
@@ -92,6 +98,10 @@ struct sqfs_block_processor_t {
 	int (*process_block)(sqfs_block_t *block, sqfs_compressor_t *cmp,
 			     sqfs_u8 *scratch, size_t scratch_size);
 
+	int (*compare_frag_in_flight)(sqfs_block_processor_t *proc,
+				      sqfs_block_t *frag, sqfs_u32 index,
+				      sqfs_u32 offset);
+
 	int (*append_to_work_queue)(sqfs_block_processor_t *proc,
 				    sqfs_block_t *block);
 
@@ -101,9 +111,6 @@ struct sqfs_block_processor_t {
 SQFS_INTERNAL void block_processor_cleanup(sqfs_block_processor_t *base);
 
 SQFS_INTERNAL int block_processor_init(sqfs_block_processor_t *base,
-				       size_t max_block_size,
-				       sqfs_compressor_t *cmp,
-				       sqfs_block_writer_t *wr,
-				       sqfs_frag_table_t *tbl);
+				       const sqfs_block_processor_desc_t *desc);
 
 #endif /* INTERNAL_H */
diff --git a/lib/sqfs/block_processor/serial.c b/lib/sqfs/block_processor/serial.c
index 4d6b3ec..b20d5b0 100644
--- a/lib/sqfs/block_processor/serial.c
+++ b/lib/sqfs/block_processor/serial.c
@@ -61,27 +61,46 @@ static int block_processor_sync(sqfs_block_processor_t *proc)
 	return ((serial_block_processor_t *)proc)->status;
 }
 
-sqfs_block_processor_t *sqfs_block_processor_create(size_t max_block_size,
-						    sqfs_compressor_t *cmp,
-						    unsigned int num_workers,
-						    size_t max_backlog,
-						    sqfs_block_writer_t *wr,
-						    sqfs_frag_table_t *tbl)
+static int compare_frag_in_flight(sqfs_block_processor_t *proc,
+				  sqfs_block_t *frag, sqfs_u32 index,
+				  sqfs_u32 offset)
+{
+	if (proc->frag_block == NULL || index != proc->frag_block->index)
+		return -1;
+
+	if (offset >= proc->frag_block->size)
+		return -1;
+
+	if (frag->size > (proc->frag_block->size - offset))
+		return -1;
+
+	return memcmp(proc->frag_block->data + offset, frag->data, frag->size);
+}
+
+int sqfs_block_processor_create_ex(const sqfs_block_processor_desc_t *desc,
+				   sqfs_block_processor_t **out)
 {
 	serial_block_processor_t *proc;
-	(void)num_workers; (void)max_backlog;
+	int ret;
 
-	proc = alloc_flex(sizeof(*proc), 1, max_block_size);
+	if (desc->size != sizeof(sqfs_block_processor_desc_t))
+		return SQFS_ERROR_ARG_INVALID;
+
+	proc = alloc_flex(sizeof(*proc), 1, desc->max_block_size);
 	if (proc == NULL)
-		return NULL;
+		return SQFS_ERROR_ALLOC;
 
-	if (block_processor_init(&proc->base, max_block_size, cmp, wr, tbl)) {
+	ret = block_processor_init(&proc->base, desc);
+	if (ret != 0) {
 		free(proc);
-		return NULL;
+		return ret;
 	}
 
 	proc->base.sync = block_processor_sync;
 	proc->base.append_to_work_queue = append_to_work_queue;
+	proc->base.compare_frag_in_flight = compare_frag_in_flight;
 	((sqfs_object_t *)proc)->destroy = block_processor_destroy;
-	return (sqfs_block_processor_t *)proc;
+
+	*out = (sqfs_block_processor_t *)proc;
+	return 0;
 }
diff --git a/lib/sqfs/block_processor/winpthread.c b/lib/sqfs/block_processor/winpthread.c
index 3531a3b..806c749 100644
--- a/lib/sqfs/block_processor/winpthread.c
+++ b/lib/sqfs/block_processor/winpthread.c
@@ -78,6 +78,8 @@ struct compress_worker_t {
 	thread_pool_processor_t *shared;
 	sqfs_compressor_t *cmp;
 	THREAD_HANDLE thread;
+	sqfs_u32 frag_blk_index;
+	sqfs_u32 frag_blk_size;
 	sqfs_u8 scratch[];
 };
 
@@ -178,6 +180,14 @@ static THREAD_TYPE worker_proc(THREAD_ARG arg)
 			store_completed_block(shared, blk, status);
 
 		blk = get_next_work_item(shared);
+
+		if (blk != NULL && (blk->flags & SQFS_BLK_FRAGMENT_BLOCK) &&
+		    shared->base.uncmp != NULL && shared->base.file != NULL) {
+			memcpy(worker->scratch + shared->base.max_block_size,
+			       blk->data, blk->size);
+			worker->frag_blk_index = blk->index;
+			worker->frag_blk_size = blk->size;
+		}
 		UNLOCK(&shared->mtx);
 
 		if (blk == NULL)
@@ -388,40 +398,105 @@ static int append_to_work_queue(sqfs_block_processor_t *proc,
 	return status;
 }
 
+static sqfs_block_t *find_frag_blk_in_queue(sqfs_block_t *q, sqfs_u32 index)
+{
+	while (q != NULL) {
+		if ((q->flags & SQFS_BLK_FRAGMENT_BLOCK) && q->index == index)
+			break;
+		q = q->next;
+	}
+	return q;
+}
+
+static int compare_frag_in_flight(sqfs_block_processor_t *proc,
+				  sqfs_block_t *frag, sqfs_u32 index,
+				  sqfs_u32 offset)
+{
+	thread_pool_processor_t *thproc = (thread_pool_processor_t *)proc;
+	sqfs_block_t *it = NULL;
+	void *blockbuf = NULL;
+	size_t i, size = 0;
+	int ret;
+
+	if (proc->frag_block != NULL && proc->frag_block->index == index)
+		it = proc->frag_block;
+
+	if (it == NULL)
+		it = find_frag_blk_in_queue(thproc->proc_queue, index);
+
+	if (it == NULL)
+		it = find_frag_blk_in_queue(thproc->io_queue, index);
+
+	if (it == NULL)
+		it = find_frag_blk_in_queue(thproc->done, index);
+
+	if (it == NULL) {
+		for (i = 0; i < thproc->num_workers; ++i) {
+			if (thproc->workers[i]->frag_blk_index == index) {
+				size = thproc->workers[i]->frag_blk_size;
+				blockbuf = thproc->workers[i]->scratch +
+					proc->max_block_size;
+				break;
+			}
+		}
+	} else if (it->flags & SQFS_BLK_IS_COMPRESSED) {
+		proc->buffered_index = 0xFFFFFFFF;
+		blockbuf = proc->frag_buffer;
+		ret = proc->uncmp->do_block(proc->uncmp, it->data, it->size,
+					    blockbuf, proc->max_block_size);
+		if (ret <= 0)
+			return -1;
+		proc->buffered_index = it->index;
+		size = ret;
+	} else {
+		blockbuf = it->data;
+		size = it->size;
+	}
+
+	if (blockbuf == NULL || size == 0)
+		return -1;
+
+	if (offset >= size || frag->size > (size - offset))
+		return -1;
+
+	return memcmp((const char *)blockbuf + offset, frag->data, frag->size);
+}
+
 static int block_processor_sync(sqfs_block_processor_t *proc)
 {
 	return append_to_work_queue(proc, NULL);
 }
 
-sqfs_block_processor_t *sqfs_block_processor_create(size_t max_block_size,
-						    sqfs_compressor_t *cmp,
-						    unsigned int num_workers,
-						    size_t max_backlog,
-						    sqfs_block_writer_t *wr,
-						    sqfs_frag_table_t *tbl)
+int sqfs_block_processor_create_ex(const sqfs_block_processor_desc_t *desc,
+				   sqfs_block_processor_t **out)
 {
 	thread_pool_processor_t *proc;
+	unsigned int i, num_workers;
+	size_t scratch_size;
 	sigset_t oldset;
-	unsigned int i;
 	int ret;
 
-	if (num_workers < 1)
-		num_workers = 1;
+	if (desc->size != sizeof(sqfs_block_processor_desc_t))
+		return SQFS_ERROR_ARG_INVALID;
+
+	num_workers = desc->num_workers < 1 ? 1 : desc->num_workers;
 
 	proc = alloc_flex(sizeof(*proc),
 			  sizeof(proc->workers[0]), num_workers);
 	if (proc == NULL)
-		return NULL;
+		return SQFS_ERROR_ALLOC;
 
-	if (block_processor_init(&proc->base, max_block_size, cmp, wr, tbl)) {
+	ret = block_processor_init(&proc->base, desc);
+	if (ret != 0) {
 		free(proc);
-		return NULL;
+		return ret;
 	}
 
 	proc->base.sync = block_processor_sync;
 	proc->base.append_to_work_queue = append_to_work_queue;
+	proc->base.compare_frag_in_flight = compare_frag_in_flight;
 	proc->num_workers = num_workers;
-	proc->max_backlog = max_backlog;
+	proc->max_backlog = desc->max_backlog;
 	((sqfs_object_t *)proc)->destroy = block_processor_destroy;
 
 	MUTEX_INIT(&proc->mtx);
@@ -431,28 +506,40 @@ sqfs_block_processor_t *sqfs_block_processor_create(size_t max_block_size,
 	SIGNAL_DISABLE(&oldset);
 
 	for (i = 0; i < num_workers; ++i) {
+		scratch_size = desc->max_block_size;
+		if (desc->uncmp != NULL && desc->file != NULL)
+			scratch_size *= 2;
+
 		proc->workers[i] = alloc_flex(sizeof(compress_worker_t),
-					      1, max_block_size);
+					      1, scratch_size);
 
-		if (proc->workers[i] == NULL)
+		if (proc->workers[i] == NULL) {
+			ret = SQFS_ERROR_ALLOC;
 			goto fail;
+		}
 
 		proc->workers[i]->shared = proc;
-		proc->workers[i]->cmp = sqfs_copy(cmp);
+		proc->workers[i]->cmp = sqfs_copy(desc->cmp);
+		proc->workers[i]->frag_blk_index = 0xFFFFFFFF;
 
-		if (proc->workers[i]->cmp == NULL)
+		if (proc->workers[i]->cmp == NULL) {
+			ret = SQFS_ERROR_ALLOC;
 			goto fail;
+		}
 
 		ret = THREAD_CREATE(&proc->workers[i]->thread,
 				    worker_proc, proc->workers[i]);
-		if (ret != 0)
+		if (ret != 0) {
+			ret = SQFS_ERROR_INTERNAL;
 			goto fail;
+		}
 	}
 
 	SIGNAL_ENABLE(&oldset);
-	return (sqfs_block_processor_t *)proc;
+	*out = (sqfs_block_processor_t *)proc;
+	return 0;
 fail:
 	SIGNAL_ENABLE(&oldset);
 	block_processor_destroy((sqfs_object_t *)proc);
-	return NULL;
+	return ret;
 }
diff --git a/lib/util/hash_table.c b/lib/util/hash_table.c
index 63882f3..a78aeee 100644
--- a/lib/util/hash_table.c
+++ b/lib/util/hash_table.c
@@ -123,8 +123,8 @@ entry_is_present(const struct hash_table *ht, struct hash_entry *entry)
 
 static bool
 hash_table_init(struct hash_table *ht,
-                sqfs_u32 (*key_hash_function)(const void *key),
-                bool (*key_equals_function)(const void *a,
+                sqfs_u32 (*key_hash_function)(void *user, const void *key),
+                bool (*key_equals_function)(void *user, const void *a,
                                             const void *b))
 {
    ht->size_index = 0;
@@ -144,8 +144,8 @@ hash_table_init(struct hash_table *ht,
 }
 
 struct hash_table *
-hash_table_create(sqfs_u32 (*key_hash_function)(const void *key),
-                  bool (*key_equals_function)(const void *a,
+hash_table_create(sqfs_u32 (*key_hash_function)(void *user, const void *key),
+                  bool (*key_equals_function)(void *user, const void *a,
                                               const void *b))
 {
    struct hash_table *ht;
@@ -220,7 +220,7 @@ hash_table_search(struct hash_table *ht, sqfs_u32 hash, const void *key)
       if (entry_is_free(entry)) {
          return NULL;
       } else if (entry_is_present(ht, entry) && entry->hash == hash) {
-         if (ht->key_equals_function(key, entry->key)) {
+         if (ht->key_equals_function(ht->user, key, entry->key)) {
             return entry;
          }
       }
@@ -243,7 +243,8 @@ struct hash_entry *
 hash_table_search_pre_hashed(struct hash_table *ht, sqfs_u32 hash,
                              const void *key)
 {
-   assert(ht->key_hash_function == NULL || hash == ht->key_hash_function(key));
+   assert(ht->key_hash_function == NULL ||
+          hash == ht->key_hash_function(ht->user, key));
    return hash_table_search(ht, hash, key);
 }
 
@@ -349,7 +350,7 @@ hash_table_insert(struct hash_table *ht, sqfs_u32 hash,
        */
       if (!entry_is_deleted(ht, entry) &&
           entry->hash == hash &&
-          ht->key_equals_function(key, entry->key)) {
+          ht->key_equals_function(ht->user, key, entry->key)) {
          entry->key = key;
          entry->data = data;
          return entry;
@@ -386,7 +387,8 @@ struct hash_entry *
 hash_table_insert_pre_hashed(struct hash_table *ht, sqfs_u32 hash,
                              const void *key, void *data)
 {
-   assert(ht->key_hash_function == NULL || hash == ht->key_hash_function(key));
+   assert(ht->key_hash_function == NULL ||
+          hash == ht->key_hash_function(ht->user, key));
    return hash_table_insert(ht, hash, key, data);
 }