| Message ID | 28989C0C9F1C0A428470D967B5FCED3727189D@BPXM22GP.gisp.nec.co.jp |
|---|---|
| State | Accepted, archived |
| Headers | show |
On Fri, Jan 24, 2014 at 02:55:57AM +0000, Akira Fujita wrote: > When meta_bg feature is enabled, group descriptor block is allocated > every 128 block group (or every 64 block group if 64bit feature is enabled). > > In such situation, files in block group more than #128 will be removed > if sparse_super feature is enabled with tune2fs and > afterwards necessary e2fsck running. > > Because tune2fs does not reallocate group descriptor blocks > but just set sparse_super feature. > If ext4 has sparse_super, ext2fs_descriptor_block_loc2() called > by e2fsck thinks the block group (e.g. #128) that it has group descriptor block > at the head offset. But that offset is used as backup super block before. > So e2fsck fixes ext4 based on invalid group descriptor blocks and this > cause data lost. > > The patch avoids this problem simply by disallow tune2fs enabling > sparse_super if meta_bg is enabled. > > Steps to reproduce: > > 1. Create ext4 which has meta_bg, ^sparse_super and 129+ block groups. > # mke2fs -t ext4 -O meta_bg,^resize_inode,^sparse_super DEV 17G > # mount DEV /MP > > 2. Create direcotry and files which use block group #128's metadata. > # echo $((8192*128+1)) > /sys/fs/ext4/DEV/inode_goal > # mkdir /MP/DIR > # for i in $(seq 1 100); do dd if=/dev/urandom of=/MP/DIR/file$i bs=1024 count=10; done > > 3. Enable sparse_super with tune2fs then execute e2fsck. > Data in block group #128 will be lost!! > # umount DEV > # tune2fs -O sparse_super DEV > # e2fsck/e2fsck -yf DEV > > Signed-off-by: Akira Fujita <a-fujita@rs.jp.ne.cocm> Applied, thanks. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/misc/tune2fs.c b/misc/tune2fs.c index 0eddf6d..51a4478 100644 --- a/misc/tune2fs.c +++ b/misc/tune2fs.c @@ -919,6 +919,19 @@ static int update_feature_set(ext2_filsys fs, char *features) return 1; } } + + if (FEATURE_ON(E2P_FEATURE_RO_INCOMPAT, + EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER)) { + if (sb->s_feature_incompat & + EXT2_FEATURE_INCOMPAT_META_BG) { + fputs(_("Setting filesystem feature 'sparse_super' " + "not supported\nfor filesystems with " + "the meta_bg feature enabled.\n"), + stderr); + return 1; + } + } + if (FEATURE_ON(E2P_FEATURE_INCOMPAT, EXT4_FEATURE_INCOMPAT_MMP)) { int error; @@ -2568,10 +2581,18 @@ retry_open: } if (s_flag == 1) { if (sb->s_feature_ro_compat & - EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER) + EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER) { fputs(_("\nThe filesystem already has sparse " "superblocks.\n"), stderr); - else { + } else if (sb->s_feature_incompat & + EXT2_FEATURE_INCOMPAT_META_BG) { + fputs(_("\nSetting the sparse super flag not " + "supported\nfor filesystems with " + "the meta_bg feature enabled.\n"), + stderr); + rc = 1; + goto closefs; + } else { sb->s_feature_ro_compat |= EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER; sb->s_state &= ~EXT2_VALID_FS; @@ -2581,7 +2602,7 @@ retry_open: } } if (s_flag == 0) { - fputs(_("\nClearing the sparse superflag not supported.\n"), + fputs(_("\nClearing the sparse super flag not supported.\n"), stderr); rc = 1; goto closefs;
When meta_bg feature is enabled, group descriptor block is allocated every 128 block group (or every 64 block group if 64bit feature is enabled). In such situation, files in block group more than #128 will be removed if sparse_super feature is enabled with tune2fs and afterwards necessary e2fsck running. Because tune2fs does not reallocate group descriptor blocks but just set sparse_super feature. If ext4 has sparse_super, ext2fs_descriptor_block_loc2() called by e2fsck thinks the block group (e.g. #128) that it has group descriptor block at the head offset. But that offset is used as backup super block before. So e2fsck fixes ext4 based on invalid group descriptor blocks and this cause data lost. The patch avoids this problem simply by disallow tune2fs enabling sparse_super if meta_bg is enabled. Steps to reproduce: 1. Create ext4 which has meta_bg, ^sparse_super and 129+ block groups. # mke2fs -t ext4 -O meta_bg,^resize_inode,^sparse_super DEV 17G # mount DEV /MP 2. Create direcotry and files which use block group #128's metadata. # echo $((8192*128+1)) > /sys/fs/ext4/DEV/inode_goal # mkdir /MP/DIR # for i in $(seq 1 100); do dd if=/dev/urandom of=/MP/DIR/file$i bs=1024 count=10; done 3. Enable sparse_super with tune2fs then execute e2fsck. Data in block group #128 will be lost!! # umount DEV # tune2fs -O sparse_super DEV # e2fsck/e2fsck -yf DEV Signed-off-by: Akira Fujita <a-fujita@rs.jp.ne.cocm> --- misc/tune2fs.c | 27 ++++++++++++++++++++++++--- 1 file changed, 24 insertions(+), 3 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html