From: Andreas Dilger Subject: Re: [PATCH 3/3] mke2fs: prevent creation of unmountable ext4 with large flex_bg count Date: Wed, 11 Jun 2014 13:01:29 -0600 Message-ID: <6A410081-0492-4378-BA66-07AFA7C0DEAF@dilger.ca> References: <28989C0C9F1C0A428470D967B5FCED372A7EA3@BPXM22GP.gisp.nec.co.jp> Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.2\)) Content-Type: multipart/signed; boundary="Apple-Mail=_377DC749-8689-4B3E-AC29-3D8165459AB1"; protocol="application/pgp-signature"; micalg=pgp-sha1 Cc: Theodore Tso , Ext4 Developers List To: Akira Fujita Return-path: Received: from mail-pa0-f54.google.com ([209.85.220.54]:52321 "EHLO mail-pa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752572AbaFKTBU (ORCPT ); Wed, 11 Jun 2014 15:01:20 -0400 Received: by mail-pa0-f54.google.com with SMTP id et14so94904pad.41 for ; Wed, 11 Jun 2014 12:01:20 -0700 (PDT) In-Reply-To: <28989C0C9F1C0A428470D967B5FCED372A7EA3@BPXM22GP.gisp.nec.co.jp> Sender: linux-ext4-owner@vger.kernel.org List-ID: --Apple-Mail=_377DC749-8689-4B3E-AC29-3D8165459AB1 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii On Jun 11, 2014, at 2:38 AM, Akira Fujita = 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). >=20 > 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 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 >=20 > 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 >=20 > 3. > # dumpe2fs DEV > > Block count: 2130483 > > Flex block group size: 1048576=20 > > 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:=20 > Free inodes: 525201-533280 >=20 > (Case2) > 1. > # mke2fs -t ext4 -G 2147483648 DEV 3145728 >=20 > 2. > # debugfs -R stats DEV > > Block count: 786432 > > Flex block group size: 2147483648 > > Group 0: block bitmap at 193, inode bitmap at 194, inode table at 195 = <--=20 > 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] > >=20 > Signed-off-by: Akira Fujita > --- > 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 =3D 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: > } >=20 > /* > + * 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 =3D 1 << fs->super->s_log_groups_per_flex; > + flexbg_overhead =3D 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 =3D 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@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html Cheers, Andreas --Apple-Mail=_377DC749-8689-4B3E-AC29-3D8165459AB1 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP using GPGMail -----BEGIN PGP SIGNATURE----- Comment: GPGTools - http://gpgtools.org iQIVAwUBU5ininKl2rkXzB/gAQI4xxAAp/NJjaeEyr4+r31lKg9io1a7xyxp82b2 RPYKCv4Dkc3/qMeIV0EsWCuAlx24pxVZd6LqVR3iizeM/9MYeViTAyYaSdaVekow 6LKgm1qnFXc0XjdvNKt3Q0UJ4hBk23+EXY/Tx8V/E0AtzsTXmrTlBgZO2CYDKkmI Zx1AnIL14fFwW1TNVj/2M7n3mAk8zNYF4ne2NrWQOwKs2srvdKBf9ErKWHb2NOGG 9mv8k5E0G1NmscgZSuW0/JSamkGenTJc0Iq9SdVcQFZbldlxp/GjeN9qbYrFVcPA 62kOIRY9rbnIiXnvvA4ox5H5QyQjl7p+tH1t9iVsk6R1md5MSayLVNneFtKOZ7qV eC1U5z5zABhI8Vszryljmu+EIMYe0x4vFWIZm2H/NKYVLeC23iT7viTtzapGjRl8 OIepSz54HxpdFm9gJlF1JLgH7sypTERsw3VOB5jRJqdSGf6ImaFN3biIy5bYlfxp wfo6BiYvDzAOnCllrzVTqvHxm+K4m0sCh05sB9FJ2ENDgqu19L0Y4+MD1cwEcR+x kEYG1VijmKzVT9Ka0UfMwXWX2dpCcE+duN4bgYy7bBvPtiUGKvAHtKkhGfKXGQUr CmbJpnSNvym0gKCi0x91AaW6dOOfIRhBszTvOg+vIrmD/2ExUNH4Rmf4K1ExfOnv I0LFmxq6gv0= =Vyt8 -----END PGP SIGNATURE----- --Apple-Mail=_377DC749-8689-4B3E-AC29-3D8165459AB1--