btrfs: Remove redundant FLAG_VACANCY

Commit 9036c10208e1 ("Btrfs: update hole handling v2") added the
FLAG_VACANCY to denote holes, however there was already a consistent way
of flagging extents which represent hole - ->block_start =
EXTENT_MAP_HOLE. And also the only place where this flag is checked is
in the fiemap code, but the block_start value is also checked and every
other place in the filesystem detects holes by using block_start
value's. So remove the extra flag. This survived a full xfstest run.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -4311,10 +4311,8 @@ static struct extent_map *get_extent_skip_holes(struct inode *inode,
 			return em;
 
 		/* if this isn't a hole return it */
-		if (!test_bit(EXTENT_FLAG_VACANCY, &em->flags) &&
-		    em->block_start != EXTENT_MAP_HOLE) {
+		if (em->block_start != EXTENT_MAP_HOLE)
 			return em;
-		}
 
 		/* this is a hole, advance to the next extent */
 		offset = extent_map_end(em);

fs/btrfs/extent_map.h

@@ -13,7 +13,6 @@
 /* bits for the flags field */
 #define EXTENT_FLAG_PINNED 0 /* this entry not yet on disk, don't free it */
 #define EXTENT_FLAG_COMPRESSED 1
-#define EXTENT_FLAG_VACANCY 2 /* no file extent item found */
 #define EXTENT_FLAG_PREALLOC 3 /* pre-allocated extent */
 #define EXTENT_FLAG_LOGGING 4 /* Logging this extent */
 #define EXTENT_FLAG_FILLING 5 /* Filling in a preallocated extent */

fs/btrfs/inode.c

@@ -7118,7 +7118,6 @@ not_found:
 	em->len = len;
 not_found_em:
 	em->block_start = EXTENT_MAP_HOLE;
-	set_bit(EXTENT_FLAG_VACANCY, &em->flags);
 insert:
 	btrfs_release_path(path);
 	if (em->start > start || extent_map_end(em) <= start) {

fs/btrfs/tests/inode-tests.c

@@ -288,10 +288,6 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 		test_msg("Expected a hole, got %llu\n", em->block_start);
 		goto out;
 	}
-	if (!test_bit(EXTENT_FLAG_VACANCY, &em->flags)) {
-		test_msg("Vacancy flag wasn't set properly\n");
-		goto out;
-	}
 	free_extent_map(em);
 	btrfs_drop_extent_cache(BTRFS_I(inode), 0, (u64)-1, 0);
 
@@ -1130,7 +1126,6 @@ int btrfs_test_inodes(u32 sectorsize, u32 nodesize)
 	int ret;
 
 	set_bit(EXTENT_FLAG_COMPRESSED, &compressed_only);
-	set_bit(EXTENT_FLAG_VACANCY, &vacancy_only);
 	set_bit(EXTENT_FLAG_PREALLOC, &prealloc_only);
 
 	test_msg("Running btrfs_get_extent tests\n");

include/trace/events/btrfs.h

@@ -193,7 +193,6 @@ DEFINE_EVENT(btrfs__inode, btrfs_inode_evict,
 	__print_flags(flag, "|",					\
 		{ (1 << EXTENT_FLAG_PINNED), 		"PINNED" 	},\
 		{ (1 << EXTENT_FLAG_COMPRESSED), 	"COMPRESSED" 	},\
-		{ (1 << EXTENT_FLAG_VACANCY), 		"VACANCY" 	},\
 		{ (1 << EXTENT_FLAG_PREALLOC), 		"PREALLOC" 	},\
 		{ (1 << EXTENT_FLAG_LOGGING),	 	"LOGGING" 	},\
 		{ (1 << EXTENT_FLAG_FILLING),	 	"FILLING" 	},\