Add support for storing xattr values out-of-line

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

1 files changed, 102 insertions, 10 deletions

diff --git a/lib/sqfs/write_xattr.c b/lib/sqfs/write_xattr.c
index 89c65db..33b0521 100644
--- a/lib/sqfs/write_xattr.c
+++ b/lib/sqfs/write_xattr.c
@@ -38,7 +38,8 @@ bool sqfs_has_xattr(const char *key)
 	return get_prefix(key) >= 0;
 }
 
-static int write_key(meta_writer_t *mw, const char *key, tree_xattr_t *xattr)
+static int write_key(meta_writer_t *mw, const char *key, tree_xattr_t *xattr,
+		     bool value_is_ool)
 {
 	const char *orig_key = key;
 	sqfs_xattr_entry_t kent;
@@ -54,6 +55,9 @@ static int write_key(meta_writer_t *mw, const char *key, tree_xattr_t *xattr)
 	assert(key != NULL);
 	++key;
 
+	if (value_is_ool)
+		type |= SQUASHFS_XATTR_FLAG_OOL;
+
 	kent.type = htole16(type);
 	kent.size = htole16(strlen(key));
 
@@ -67,14 +71,20 @@ static int write_key(meta_writer_t *mw, const char *key, tree_xattr_t *xattr)
 }
 
 static int write_value(meta_writer_t *mw, const char *value,
-		       tree_xattr_t *xattr)
+		       tree_xattr_t *xattr, uint64_t *value_ref_out)
 {
 	sqfs_xattr_value_t vent;
+	uint32_t offset;
+	uint64_t block;
 
 	vent.size = htole32(strlen(value));
 
 	if (meta_writer_append(mw, &vent, sizeof(vent)))
 		return -1;
+
+	meta_writer_get_position(mw, &block, &offset);
+	*value_ref_out = (block << 16) | (offset & 0xFFFF);
+
 	if (meta_writer_append(mw, value, strlen(value)))
 		return -1;
 
@@ -82,10 +92,55 @@ static int write_value(meta_writer_t *mw, const char *value,
 	return 0;
 }
 
-static int write_kv_pairs(fstree_t *fs, meta_writer_t *mw, tree_xattr_t *xattr)
+static int write_value_ool(meta_writer_t *mw, uint64_t location,
+			   tree_xattr_t *xattr)
+{
+	sqfs_xattr_value_t vent;
+	uint64_t ref;
+
+	vent.size = htole32(sizeof(location));
+	if (meta_writer_append(mw, &vent, sizeof(vent)))
+		return -1;
+
+	ref = htole64(location);
+	if (meta_writer_append(mw, &ref, sizeof(ref)))
+		return -1;
+
+	xattr->size += sizeof(vent) + sizeof(ref);
+	return 0;
+}
+
+static bool should_store_ool(fstree_t *fs, const char *value, size_t index)
+{
+	size_t refcount;
+
+	refcount = str_table_get_ref_count(&fs->xattr_values, index);
+	if (refcount < 2)
+		return false;
+
+	/*
+	  Storing in line needs this many bytes: refcount * len
+
+	  Storing out-of-line needs this many: len + (refcount - 1) * 8
+
+	  Out-of-line prefereable if:
+	      refcount * len > len + (refcount - 1) * 8
+	   => refcount * len - len > (refcount - 1) * 8
+	   => (refcount - 1) * len > (refcount - 1) * 8
+	   => len > 8
+
+	   Note that this only holds iff refcount - 1 != 0, i.e. refcount > 1,
+	   otherwise we would be dividing by 0 in the 3rd step.
+	 */
+	return strlen(value) > sizeof(uint64_t);
+}
+
+static int write_kv_pairs(fstree_t *fs, meta_writer_t *mw, tree_xattr_t *xattr,
+			  uint64_t *ool_locations)
 {
 	uint32_t key_idx, val_idx;
 	const char *key, *value;
+	uint64_t ref;
 	size_t i;
 
 	for (i = 0; i < xattr->num_attr; ++i) {
@@ -95,20 +150,50 @@ static int write_kv_pairs(fstree_t *fs, meta_writer_t *mw, tree_xattr_t *xattr)
 		key = str_table_get_string(&fs->xattr_keys, key_idx);
 		value = str_table_get_string(&fs->xattr_values, val_idx);
 
-		if (write_key(mw, key, xattr))
-			return -1;
+		if (ool_locations[val_idx] == 0xFFFFFFFFFFFFFFFF) {
+			if (write_key(mw, key, xattr, false))
+				return -1;
+
+			if (write_value(mw, value, xattr, &ref))
+				return -1;
 
-		if (write_value(mw, value, xattr))
-			return -1;
+			if (should_store_ool(fs, value, val_idx))
+				ool_locations[val_idx] = ref;
+		} else {
+			if (write_key(mw, key, xattr, true))
+				return -1;
+
+			if (write_value_ool(mw, ool_locations[val_idx], xattr))
+				return -1;
+		}
 	}
 
 	return 0;
 }
 
+static uint64_t *create_ool_locations_table(fstree_t *fs)
+{
+	uint64_t *table;
+	size_t i;
+
+	table = malloc(sizeof(uint64_t) * fs->xattr_values.num_strings);
+
+	if (table == NULL) {
+		perror("allocating Xattr OOL locations table");
+		return NULL;
+	}
+
+	for (i = 0; i < fs->xattr_values.num_strings; ++i) {
+		table[i] = 0xFFFFFFFFFFFFFFFFUL;
+	}
+
+	return table;
+}
+
 int write_xattr(int outfd, fstree_t *fs, sqfs_super_t *super,
 		compressor_t *cmp)
 {
-	uint64_t kv_start, id_start, block, *tbl;
+	uint64_t kv_start, id_start, block, *tbl, *ool_locations;
 	size_t i = 0, count = 0, blocks;
 	sqfs_xattr_id_table_t idtbl;
 	sqfs_xattr_id_t id_ent;
@@ -119,9 +204,13 @@ int write_xattr(int outfd, fstree_t *fs, sqfs_super_t *super,
 	if (fs->xattr == NULL)
 		return 0;
 
+	ool_locations = create_ool_locations_table(fs);
+	if (ool_locations == NULL)
+		return -1;
+
 	mw = meta_writer_create(outfd, cmp, false);
 	if (mw == NULL)
-		return -1;
+		goto fail_ool;
 
 	/* write xattr key-value pairs */
 	kv_start = super->bytes_used;
@@ -130,7 +219,7 @@ int write_xattr(int outfd, fstree_t *fs, sqfs_super_t *super,
 		meta_writer_get_position(mw, &it->block, &it->offset);
 		it->size = 0;
 
-		if (write_kv_pairs(fs, mw, it))
+		if (write_kv_pairs(fs, mw, it, ool_locations))
 			goto fail_mw;
 
 		++count;
@@ -201,10 +290,13 @@ int write_xattr(int outfd, fstree_t *fs, sqfs_super_t *super,
 
 	free(tbl);
 	meta_writer_destroy(mw);
+	free(ool_locations);
 	return 0;
 fail_tbl:
 	free(tbl);
 fail_mw:
 	meta_writer_destroy(mw);
+fail_ool:
+	free(ool_locations);
 	return -1;
 }