On Jun 11, 2014, at 2:38 AM, Akira Fujita <a-fujita@xxxxxxxxxxxxx> wrote: > In mke2fs command, if flex_bg count is too large to filesystem blocks count, > unmountable ext4 which has the out of filesystem block offset is created (Case1). > Moreover this large flex_bg count causes an unintentional metadata layout > (bmap-imap-itable-bmap-imap-itable .. in block group) (Case2). > > To fix these issues and keep healthy flex_bg layout, disallow creating ext4 > with obviously large flex_bg count to filesystem blocks count. Patch looks good to me. Reviewed-by: Andreas Dilger <adilger@xxxxxxxxx> This also reminds me of my previous flex_bg patch: [PATCH][RFC] mke2fs: handle flex_bg collision with backup descriptors http://permalink.gmane.org/gmane.comp.file-systems.ext4/42298 which fixes the "bmap-imap-itable-bmap-imap-itable" problem when a large flex_bg size is used. Sadly, there were no comments on that patch. Cheers, Andreas > Steps to reproduce: > (Case1) > 1. > # mke2fs -t ext4 -b 4096 -O ^resize_inode -G $((2**20)) DEV 2130483 > > 2. > # mount -t ext4 DEV MP > mount: wrong fs type, bad option, bad superblock on /dev/sdb4, > missing codepage or helper program, or other error > In some cases useful info is found in syslog - try > dmesg | tail or so > > 3. > # dumpe2fs DEV > <snip> > Block count: 2130483 > <snip> > Flex block group size: 1048576 > <snip> > Group 65: (Blocks 2129920-2130482) [INODE_UNINIT] > Checksum 0x4cb3, unused inodes 8080 > Block bitmap at 67 (bg #0 + 67), Inode bitmap at 1048643 (bg #32 + 67) > Inode table at 2129979-2130483 (+59) <---- 2130483 is out of FS! > 65535 free blocks, 8080 free inodes, 0 directories, 8080 unused inodes > Free blocks: > Free inodes: 525201-533280 > > (Case2) > 1. > # mke2fs -t ext4 -G 2147483648 DEV 3145728 > > 2. > # debugfs -R stats DEV > <snip> > Block count: 786432 > <snip> > Flex block group size: 2147483648 > <snip> > Group 0: block bitmap at 193, inode bitmap at 194, inode table at 195 <-- > 20233 free blocks, 8181 free inodes, 2 used directories, 8181 unused inodes > [Checksum 0xa597] > Group 1: block bitmap at 707, inode bitmap at 708, inode table at 709 <-- > 32575 free blocks, 8192 free inodes, 0 used directories, 8192 unused inodes > [Inode not init, Block not init, Checksum 0x196f] > Group 2: block bitmap at 1221, inode bitmap at 1222, inode table at 1223 <-- > 32768 free blocks, 8192 free inodes, 0 used directories, 8192 unused inodes > [Inode not init, Block not init, Checksum 0x856f] > <snip> > > Signed-off-by: Akira Fujita <a-fujita@xxxxxxxxxxxxx> > --- > lib/ext2fs/initialize.c | 24 ++++++++++++++++++++++++ > 1 file changed, 24 insertions(+) > diff --git a/lib/ext2fs/initialize.c b/lib/ext2fs/initialize.c > index 75fbf8e..34753d0 100644 > --- a/lib/ext2fs/initialize.c > +++ b/lib/ext2fs/initialize.c > @@ -91,8 +91,10 @@ errcode_t ext2fs_initialize(const char *name, int flags, > unsigned int rem; > unsigned int overhead = 0; > unsigned int ipg; > + unsigned int flexbg_size; > dgrp_t i; > blk64_t free_blocks; > + blk64_t flexbg_overhead; > blk_t numblocks; > int rsv_gdt; > int csum_flag; > @@ -419,6 +421,28 @@ ipg_retry: > } > > /* > + * Calculate the flex_bg related metadata blocks count. > + * It includes the boot block, the super block, > + * the block group descriptors, the reserved gdt blocks, > + * the block bitmaps, the inode bitmaps and the inode tables. > + * This is a simple check, so that the backup superblock and > + * other feature related blocks are not considered. > + */ > + flexbg_size = 1 << fs->super->s_log_groups_per_flex; > + flexbg_overhead = super->s_first_data_block + 1 + > + fs->desc_blocks + super->s_reserved_gdt_blocks + > + (__u64)flexbg_size * (2 + fs->inode_blocks_per_group); > + > + /* > + * Disallow creating ext4 which breaks flex_bg metadata layout > + * obviously. > + */ > + if (flexbg_overhead > ext2fs_blocks_count(fs->super)) { > + retval = EXT2_ET_INVALID_ARGUMENT; > + goto cleanup; > + } > + > + /* > * At this point we know how big the filesystem will be. So > * we can do any and all allocations that depend on the block > * count. > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html Cheers, Andreas
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