[PATCH 2/4] btrfs-progs: fsck: Introduce --fix-dev-size option

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

Introduce --fix-dev-size option to fix device related problems.

This repairing  is also included in --repair, but considering the safety
and potential affected users, it's better to provide a option to fix and
only fix device size related problem to avoid full --repair.

Reported-by: Asif Youssuff <yoasif@gmail.com>
Reported-by: Rich Rauenzahn <rrauenza@gmail.com>
Signed-off-by: Qu Wenruo <quwenruo.btrfs@gmx.com>
---
 Documentation/btrfs-check.asciidoc | 23 +++++++++++++++++++++++
 cmds-check.c                       | 28 +++++++++++++++++++++++++++-
 2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/Documentation/btrfs-check.asciidoc b/Documentation/btrfs-check.asciidoc
index fbf48847ac25..e45c7a457bac 100644
--- a/Documentation/btrfs-check.asciidoc
+++ b/Documentation/btrfs-check.asciidoc
@@ -93,6 +93,29 @@ the entire free space cache. This option with 'v2' provides an alternative
 method of clearing the free space cache that doesn't require mounting the
 filesystem.
 
+--fix-dev-size::
+From v4.14-rc kernels, a more restrict device size checker is introduced, while
+old kernel doesn't strictly align its device size, so it may cause noisy kernel
+warning for newer kernel, like:
++
+....
+WARNING: CPU: 3 PID: 439 at fs/btrfs/ctree.h:1559 btrfs_update_device+0x1c5/0x1d0 [btrfs]
+....
++
+And for some case where super block total device size may mismatch with all
+devices, and the filesystem will be unable to be mounted, with kernel message
+like:
++
+....
+BTRFS error (device sdb): super_total_bytes 92017859088384 mismatch with fs_devices total_rw_bytes 92017859094528 
+....
++
+This option will fix both problems by aligning all size of devices, and
+re-calculating superblock total bytes.
++
+Although such repairing is included in *--repair* option, considering the
+safety of *--repair*, this option is provided to suppress all other dangerous
+repairing and only fix device sizes related problems.
 
 DANGEROUS OPTIONS
 -----------------
diff --git a/cmds-check.c b/cmds-check.c
index 007781fa5d1b..fdb6d832eee1 100644
--- a/cmds-check.c
+++ b/cmds-check.c
@@ -11746,6 +11746,8 @@ out:
 	return err;
 }
 
+static int reset_devs_size(struct btrfs_fs_info *fs_info);
+
 static int do_check_chunks_and_extents(struct btrfs_fs_info *fs_info)
 {
 	int ret;
@@ -11756,6 +11758,12 @@ static int do_check_chunks_and_extents(struct btrfs_fs_info *fs_info)
 		ret = check_chunks_and_extents_v2(fs_info);
 	else
 		ret = check_chunks_and_extents(fs_info);
+	/* Also repair device sizes if needed */
+	if (repair && !ret) {
+		ret = reset_devs_size(fs_info);
+		if (ret > 0)
+			ret = 0;
+	}
 
 	return ret;
 }
@@ -13088,6 +13096,8 @@ const char * const cmd_check_usage[] = {
 	"-b|--backup                 use the first valid backup root copy",
 	"--force                     skip mount checks, repair is not possible",
 	"--repair                    try to repair the filesystem",
+	"--fix-dev-size              repair device size related problem",
+	"                            will not trigger other repair",
 	"--readonly                  run in read-only mode (default)",
 	"--init-csum-tree            create a new CRC tree",
 	"--init-extent-tree          create a new extent tree",
@@ -13128,6 +13138,7 @@ int cmd_check(int argc, char **argv)
 	int qgroups_repaired = 0;
 	unsigned ctree_flags = OPEN_CTREE_EXCLUSIVE;
 	int force = 0;
+	bool fix_dev_size = false;
 
 	while(1) {
 		int c;
@@ -13135,7 +13146,7 @@ int cmd_check(int argc, char **argv)
 			GETOPT_VAL_INIT_EXTENT, GETOPT_VAL_CHECK_CSUM,
 			GETOPT_VAL_READONLY, GETOPT_VAL_CHUNK_TREE,
 			GETOPT_VAL_MODE, GETOPT_VAL_CLEAR_SPACE_CACHE,
-			GETOPT_VAL_FORCE };
+			GETOPT_VAL_FORCE, GETOPT_VAL_FIX_DEV_SIZE };
 		static const struct option long_options[] = {
 			{ "super", required_argument, NULL, 's' },
 			{ "repair", no_argument, NULL, GETOPT_VAL_REPAIR },
@@ -13158,6 +13169,8 @@ int cmd_check(int argc, char **argv)
 			{ "clear-space-cache", required_argument, NULL,
 				GETOPT_VAL_CLEAR_SPACE_CACHE},
 			{ "force", no_argument, NULL, GETOPT_VAL_FORCE },
+			{ "fix-dev-size", no_argument, NULL,
+				GETOPT_VAL_FIX_DEV_SIZE },
 			{ NULL, 0, NULL, 0}
 		};
 
@@ -13245,6 +13258,11 @@ int cmd_check(int argc, char **argv)
 			case GETOPT_VAL_FORCE:
 				force = 1;
 				break;
+			case GETOPT_VAL_FIX_DEV_SIZE:
+				fix_dev_size = true;
+				repair = 1;
+				ctree_flags |= OPEN_CTREE_WRITES;
+				break;
 		}
 	}
 
@@ -13371,6 +13389,14 @@ int cmd_check(int argc, char **argv)
 			report_qgroups(1);
 		goto close_out;
 	}
+
+	if (fix_dev_size) {
+		ret = reset_devs_size(info);
+		if (ret > 0)
+			ret = 0;
+		err |= !!ret;
+		goto close_out;
+	}
 	if (subvolid) {
 		printf("Print extent state for subvolume %llu on %s\nUUID: %s\n",
 		       subvolid, argv[optind], uuidbuf);
-- 
2.14.2