http://bugzilla.kernel.org/show_bug.cgi?id=12534
Summary: ext4 extent structure backwards
Product: File System
Version: 2.5
KernelVersion: 2.6.28
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: ext4
AssignedTo: [email protected]
ReportedBy: [email protected]
Latest working kernel version: 2.6.28
Earliest failing kernel version: 2.6.28
Distribution: Gentoo
Hardware Environment: i686
I was figuring out ext4 with hexedit (don't ask), and I noticed that the extent
structure is backwards. It's defined in ext4_extents.h with this order:
block(32-bit), len(16), start_hi(16), start_lo(32)
Here's what I see (including 12 byte header):
0A F3 01 00 04 00 00 00 00 00 00 00
00 00 00 00 01 00 00 00 3E 17 13 00
(another 36 bytes of zeros)
You can see that the block is 0x13173e, len is 1, and start is 0. (The
header's just fine, and only says that there is 1 extent and there can be no
more than 4 extents.)
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http://bugzilla.kernel.org/show_bug.cgi?id=12534
[email protected] changed:
What |Removed |Added
----------------------------------------------------------------------------
AssignedTo|[email protected]|[email protected]
Status|NEW |ASSIGNED
------- Comment #1 from [email protected] 2009-01-24 08:07 -------
It'd be a good trick to have the on-disk format not match the header ;)
For this file:
debugfs: stat testfile
Inode: 12 Type: regular Mode: 0644 Flags: 0x80000
Generation: 1797761550 Version: 0x00000000:00000001
User: 0 Group: 0 Size: 98304
File ACL: 0 Directory ACL: 0
Links: 1 Blockcount: 128
Fragment: Address: 0 Number: 0 Size: 0
ctime: 0x497b8705:5cc91558 -- Sat Jan 24 15:24:21 2009
atime: 0x497b86f8:c29715dc -- Sat Jan 24 15:24:08 2009
mtime: 0x497b8705:5cc91558 -- Sat Jan 24 15:24:21 2009
crtime: 0x497b86f8:c29715dc -- Sat Jan 24 15:24:08 2009
Size of extra inode fields: 28
Extended attributes stored in inode body:
selinux = "unconfined_u:object_r:file_t:s0\000" (32)
BLOCKS:
(8-23):9256-9271
TOTAL: 16
(logical start 0x8, len 0x10, physical start 0x2428)
the inode looks like this:
00421b00 a4 81 00 00 00 80 01 00 f8 86 7b 49 4b 87 7b 49 |..........{IK.{I|
00421b10 05 87 7b 49 00 00 00 00 00 00 01 00 80 00 00 00 |..{I............|
00421b20 00 00 08 00 01 00 00 00 0a f3 01 00 04 00 00 00 |................|
00421b30 00 00 00 00 08 00 00 00 10 00 00 00 28 24 00 00 |............($..|
00421b40 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00421b60 00 00 00 00 0e aa 27 6b 00 00 00 00 00 00 00 00 |......'k........|
00421b70 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00421b80 1c 00 00 00 6c 19 d5 e2 58 15 c9 5c dc 15 97 c2 |....l...X..\....|
00421b90 f8 86 7b 49 dc 15 97 c2 00 00 00 00 00 00 02 ea |..{I............|
00421ba0 07 06 40 00 00 00 00 00 20 00 00 00 00 00 00 00 |..@..... .......|
00421bb0 73 65 6c 69 6e 75 78 00 04 01 38 00 00 00 00 00 |selinux...8.....|
00421bc0 05 00 00 00 00 00 00 00 61 74 74 72 00 00 00 00 |........attr....|
00421bd0 00 00 00 00 00 00 00 00 76 34 6c 75 65 00 00 00 |........v4lue...|
00421be0 75 6e 63 6f 6e 66 69 6e 65 64 5f 75 3a 6f 62 6a |unconfined_u:obj|
00421bf0 65 63 74 5f 72 3a 66 69 6c 65 5f 74 3a 73 30 00 |ect_r:file_t:s0.|
An extent looks like this:
struct ext4_extent {
__le32 ee_block; /* first logical block extent covers */
__le16 ee_len; /* number of blocks covered by extent */
__le16 ee_start_hi; /* high 16 bits of physical block */
__le32 ee_start_lo; /* low 32 bits of physical block */
};
The extents portion is here:
0a f3 01 00 04 00 00 00 |................|
00421b30 00 00 00 00 08 00 00 00 10 00 00 00 28 24 00 00 |............($..|
^logical 0x8^ ^len^ ^ hi^ ^start lo^
0x16 0 0x2428
There is nothing wrong with this; you are just looking at it wrong.
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