Btrfs-progs: add support for the no holes incompat flag

This adds the flag to ctree.h, adds the feature option to mkfs to turn it on and
fixes fsck so it doesn't complain about missing hole extents in files when this
flag is set.

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>

3 files changed, 17 insertions, 3 deletions

diff --git a/cmds-check.c b/cmds-check.c
index c658879c..1569d6f4 100644
--- a/cmds-check.c
+++ b/cmds-check.c
@@ -51,6 +51,7 @@ static int found_old_backref = 0;
 static LIST_HEAD(duplicate_extents);
 static LIST_HEAD(delete_items);
 static int repair = 0;
+static int no_holes = 0;
 
 struct extent_backref {
 	struct list_head list;
@@ -456,8 +457,9 @@ static void maybe_free_inode_rec(struct cache_tree *inode_cache,
 			rec->errors |= I_ERR_FILE_NBYTES_WRONG;
 		if (rec->extent_start == (u64)-1 || rec->extent_start > 0)
 			rec->first_extent_gap = 0;
-		if (rec->nlink > 0 && (rec->extent_end < rec->isize ||
-		    rec->first_extent_gap < rec->isize))
+		if (rec->nlink > 0 && !no_holes &&
+		    (rec->extent_end < rec->isize ||
+		     rec->first_extent_gap < rec->isize))
 			rec->errors |= I_ERR_FILE_EXTENT_DISCOUNT;
 	}
 
@@ -6500,6 +6502,14 @@ int cmd_check(int argc, char **argv)
 	if (ret)
 		goto out;
 
+	/*
+	 * We used to have to have these hole extents in between our real
+	 * extents so if we don't have this flag set we need to make sure there
+	 * are no gaps in the file extents for inodes, otherwise we can just
+	 * ignore it when this happens.
+	 */
+	no_holes = btrfs_fs_incompat(root->fs_info,
+				     BTRFS_FEATURE_INCOMPAT_NO_HOLES);
 	fprintf(stderr, "checking fs roots\n");
 	ret = check_fs_roots(root, &root_cache);
 	if (ret)
diff --git a/ctree.h b/ctree.h
index 22a5c6ae..3cc3477b 100644
--- a/ctree.h
+++ b/ctree.h
@@ -470,6 +470,7 @@ struct btrfs_super_block {
 #define BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF	(1ULL << 6)
 #define BTRFS_FEATURE_INCOMPAT_RAID56		(1ULL << 7)
 #define BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA	(1ULL << 8)
+#define BTRFS_FEATURE_INCOMPAT_NO_HOLES		(1ULL << 9)
 
 
 #define BTRFS_FEATURE_COMPAT_SUPP		0ULL
@@ -482,7 +483,8 @@ struct btrfs_super_block {
 	 BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF |		\
 	 BTRFS_FEATURE_INCOMPAT_RAID56 |		\
 	 BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS |		\
-	 BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA)
+	 BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA |	\
+	 BTRFS_FEATURE_INCOMPAT_NO_HOLES)
 
 /*
  * A leaf is full of items. offset and size tell us where to find
diff --git a/mkfs.c b/mkfs.c
index aaea3682..d238b5c3 100644
--- a/mkfs.c
+++ b/mkfs.c
@@ -1147,6 +1147,8 @@ static const struct btrfs_fs_feature {
 		"raid56 extended format" },
 	{ "skinny-metadata", BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA,
 		"reduced-size metadata extent refs" },
+	{ "no-holes", BTRFS_FEATURE_INCOMPAT_NO_HOLES,
+		"no explicit hole extents for files" },
 	/* Keep this one last */
 	{ "list-all", BTRFS_FEATURE_LIST_ALL, NULL }
 };