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From:   Icenowy Zheng <icenowy@aosc.io>
To:     Jaegeuk Kim <jaegeuk@kernel.org>, Chao Yu <yuchao0@huawei.com>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, Icenowy Zheng <icenowy@aosc.io>
Subject: [PATCH v2] f2fs: use EINVAL for superblock with invalid magic
Date:   Thu, 25 Jul 2019 11:08:52 +0800
Message-Id: <20190725030852.33161-1-icenowy@aosc.io>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

The kernel mount_block_root() function expects -EACESS or -EINVAL for a
unmountable filesystem when trying to mount the root with different
filesystem types.

However, in 5.3-rc1 the behavior when F2FS code cannot find valid block
changed to return -EFSCORRUPTED(-EUCLEAN), and this error code makes
mount_block_root() fail when trying to probe F2FS.

When the magic number of the superblock mismatches, it has a high
probability that it's just not a F2FS. In this case return -EINVAL seems
to be a better result, and this return value can make mount_block_root()
probing work again.

Return -EINVAL when the superblock has magic mismatch, -EFSCORRUPTED in
other cases (the magic matches but the superblock cannot be recognized).

Fixes: 10f966bbf521 ("f2fs: use generic EFSBADCRC/EFSCORRUPTED")
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
---
Changes in v2:
- Only return -EINVAL when magic mismatch.

 fs/f2fs/super.c | 48 ++++++++++++++++++++++++------------------------
 1 file changed, 24 insertions(+), 24 deletions(-)

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 6de6cda44031..78a1b873e48a 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -2422,6 +2422,12 @@ static int sanity_check_raw_super(struct f2fs_sb_info *sbi,
 	size_t crc_offset = 0;
 	__u32 crc = 0;
 
+	if (le32_to_cpu(raw_super->magic) != F2FS_SUPER_MAGIC) {
+		f2fs_info(sbi, "Magic Mismatch, valid(0x%x) - read(0x%x)",
+			  F2FS_SUPER_MAGIC, le32_to_cpu(raw_super->magic));
+		return -EINVAL;
+	}
+
 	/* Check checksum_offset and crc in superblock */
 	if (__F2FS_HAS_FEATURE(raw_super, F2FS_FEATURE_SB_CHKSUM)) {
 		crc_offset = le32_to_cpu(raw_super->checksum_offset);
@@ -2429,26 +2435,20 @@ static int sanity_check_raw_super(struct f2fs_sb_info *sbi,
 			offsetof(struct f2fs_super_block, crc)) {
 			f2fs_info(sbi, "Invalid SB checksum offset: %zu",
 				  crc_offset);
-			return 1;
+			return -EFSCORRUPTED;
 		}
 		crc = le32_to_cpu(raw_super->crc);
 		if (!f2fs_crc_valid(sbi, crc, raw_super, crc_offset)) {
 			f2fs_info(sbi, "Invalid SB checksum value: %u", crc);
-			return 1;
+			return -EFSCORRUPTED;
 		}
 	}
 
-	if (F2FS_SUPER_MAGIC != le32_to_cpu(raw_super->magic)) {
-		f2fs_info(sbi, "Magic Mismatch, valid(0x%x) - read(0x%x)",
-			  F2FS_SUPER_MAGIC, le32_to_cpu(raw_super->magic));
-		return 1;
-	}
-
 	/* Currently, support only 4KB page cache size */
 	if (F2FS_BLKSIZE != PAGE_SIZE) {
 		f2fs_info(sbi, "Invalid page_cache_size (%lu), supports only 4KB",
 			  PAGE_SIZE);
-		return 1;
+		return -EFSCORRUPTED;
 	}
 
 	/* Currently, support only 4KB block size */
@@ -2456,14 +2456,14 @@ static int sanity_check_raw_super(struct f2fs_sb_info *sbi,
 	if (blocksize != F2FS_BLKSIZE) {
 		f2fs_info(sbi, "Invalid blocksize (%u), supports only 4KB",
 			  blocksize);
-		return 1;
+		return -EFSCORRUPTED;
 	}
 
 	/* check log blocks per segment */
 	if (le32_to_cpu(raw_super->log_blocks_per_seg) != 9) {
 		f2fs_info(sbi, "Invalid log blocks per segment (%u)",
 			  le32_to_cpu(raw_super->log_blocks_per_seg));
-		return 1;
+		return -EFSCORRUPTED;
 	}
 
 	/* Currently, support 512/1024/2048/4096 bytes sector size */
@@ -2473,7 +2473,7 @@ static int sanity_check_raw_super(struct f2fs_sb_info *sbi,
 				F2FS_MIN_LOG_SECTOR_SIZE) {
 		f2fs_info(sbi, "Invalid log sectorsize (%u)",
 			  le32_to_cpu(raw_super->log_sectorsize));
-		return 1;
+		return -EFSCORRUPTED;
 	}
 	if (le32_to_cpu(raw_super->log_sectors_per_block) +
 		le32_to_cpu(raw_super->log_sectorsize) !=
@@ -2481,7 +2481,7 @@ static int sanity_check_raw_super(struct f2fs_sb_info *sbi,
 		f2fs_info(sbi, "Invalid log sectors per block(%u) log sectorsize(%u)",
 			  le32_to_cpu(raw_super->log_sectors_per_block),
 			  le32_to_cpu(raw_super->log_sectorsize));
-		return 1;
+		return -EFSCORRUPTED;
 	}
 
 	segment_count = le32_to_cpu(raw_super->segment_count);
@@ -2495,7 +2495,7 @@ static int sanity_check_raw_super(struct f2fs_sb_info *sbi,
 	if (segment_count > F2FS_MAX_SEGMENT ||
 				segment_count < F2FS_MIN_SEGMENTS) {
 		f2fs_info(sbi, "Invalid segment count (%u)", segment_count);
-		return 1;
+		return -EFSCORRUPTED;
 	}
 
 	if (total_sections > segment_count ||
@@ -2503,25 +2503,25 @@ static int sanity_check_raw_super(struct f2fs_sb_info *sbi,
 			segs_per_sec > segment_count || !segs_per_sec) {
 		f2fs_info(sbi, "Invalid segment/section count (%u, %u x %u)",
 			  segment_count, total_sections, segs_per_sec);
-		return 1;
+		return -EFSCORRUPTED;
 	}
 
 	if ((segment_count / segs_per_sec) < total_sections) {
 		f2fs_info(sbi, "Small segment_count (%u < %u * %u)",
 			  segment_count, segs_per_sec, total_sections);
-		return 1;
+		return -EFSCORRUPTED;
 	}
 
 	if (segment_count > (le64_to_cpu(raw_super->block_count) >> 9)) {
 		f2fs_info(sbi, "Wrong segment_count / block_count (%u > %llu)",
 			  segment_count, le64_to_cpu(raw_super->block_count));
-		return 1;
+		return -EFSCORRUPTED;
 	}
 
 	if (secs_per_zone > total_sections || !secs_per_zone) {
 		f2fs_info(sbi, "Wrong secs_per_zone / total_sections (%u, %u)",
 			  secs_per_zone, total_sections);
-		return 1;
+		return -EFSCORRUPTED;
 	}
 	if (le32_to_cpu(raw_super->extension_count) > F2FS_MAX_EXTENSION ||
 			raw_super->hot_ext_count > F2FS_MAX_EXTENSION ||
@@ -2531,7 +2531,7 @@ static int sanity_check_raw_super(struct f2fs_sb_info *sbi,
 			  le32_to_cpu(raw_super->extension_count),
 			  raw_super->hot_ext_count,
 			  F2FS_MAX_EXTENSION);
-		return 1;
+		return -EFSCORRUPTED;
 	}
 
 	if (le32_to_cpu(raw_super->cp_payload) >
@@ -2539,7 +2539,7 @@ static int sanity_check_raw_super(struct f2fs_sb_info *sbi,
 		f2fs_info(sbi, "Insane cp_payload (%u > %u)",
 			  le32_to_cpu(raw_super->cp_payload),
 			  blocks_per_seg - F2FS_CP_PACKS);
-		return 1;
+		return -EFSCORRUPTED;
 	}
 
 	/* check reserved ino info */
@@ -2550,12 +2550,12 @@ static int sanity_check_raw_super(struct f2fs_sb_info *sbi,
 			  le32_to_cpu(raw_super->node_ino),
 			  le32_to_cpu(raw_super->meta_ino),
 			  le32_to_cpu(raw_super->root_ino));
-		return 1;
+		return -EFSCORRUPTED;
 	}
 
 	/* check CP/SIT/NAT/SSA/MAIN_AREA area boundary */
 	if (sanity_check_area_boundary(sbi, bh))
-		return 1;
+		return -EFSCORRUPTED;
 
 	return 0;
 }
@@ -2870,10 +2870,10 @@ static int read_raw_super_block(struct f2fs_sb_info *sbi,
 		}
 
 		/* sanity checking of raw super */
-		if (sanity_check_raw_super(sbi, bh)) {
+		err = sanity_check_raw_super(sbi, bh);
+		if (err) {
 			f2fs_err(sbi, "Can't find valid F2FS filesystem in %dth superblock",
 				 block + 1);
-			err = -EFSCORRUPTED;
 			brelse(bh);
 			continue;
 		}
-- 
2.21.0