From: Eric Sandeen <sandeen@redhat.com>
To: Leonard Michlmayr <leonard.michlmayr@gmail.com>
Cc: Akira Fujita <a-fujita@rs.jp.nec.com>,
tytso@mit.edu, Ext4 Developers List <linux-ext4@vger.kernel.org>
Subject: Re: [PATCH 11/28] ext4: correctly calculate number of blocks for fiemap
Date: Thu, 04 Mar 2010 17:38:50 -0600 [thread overview]
Message-ID: <4B90448A.2030609@redhat.com> (raw)
In-Reply-To: <1267739098.4204.12.camel@michlmayr>
Leonard Michlmayr wrote:
> Akira Fujita:
>> <kernel-space>
>> fs/ioctl.c ioctl_fimap():
>>
>> filemap_check_ranges():
>> len(~0ULL)
>> new_len(4398046511103 = s_maxbytes) <--- Because 'len > s_maxbytes'
>>
>> fs/ext4/extents.c ext4_fiemap():
>> last_blk = start(0) + len(4398046511103) - 1 >> s_blocksize_bits(11)
>> = 4294967295 (0xFFFFFFFF)
>> len_blks = 4294967295 + 1 (0xFFFFFFFF + 0x00000001)
>> = 4294967296 (0x100000000) <--- _OVERFLOW!!_
>>
>> ext4_ext_walk_space():
>> num = 0
>>
>> This overflow leads to incorrect output like the below,
>> even though 2 extents exist.
>>
>
> Thank you for pointing this out. I had not checked s_maxbytes.
> Appearently s_maxbytes can be 1<<(32 + s_blocksize_bits) - 1. Therefore
> the number of blocks in a file cannot be stored in a 32bit integer.
For extent-based files it had better be....
struct ext4_extent {
__le32 ee_block; /* first logical block extent covers */
__le16 ee_len; /* number of blocks covered by extent */
The start block can't be more than 32 bits; this essentially limits
the file size / maximum logical block to 2^32 blocks right?
s_maxbytes comes out to 17592186044415
2^32 4k blocks is 17592186044416 bytes, or max byte offset 17592186044415
What am I missing? (confusion between max byte count and max
byte offset, perhaps?)
-Eric
> I have a patch that should fix it for fiemap. I have just compiled it
> and I will do some testing and double checking tomorrow. I will send a
> separate email with the patch.
>
> regards
> Leonard
>
>
> --
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next prev parent reply other threads:[~2010-03-04 23:39 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-02 18:18 [PATCH 00/28] Ext4 patch queue for the 2.6.34 merge window Theodore Ts'o
2010-03-02 18:18 ` [PATCH 01/28] ext4: fix async i/o writes beyond 4GB to a sparse file Theodore Ts'o
2010-03-02 18:18 ` [PATCH 02/28] ext4: Fix optional-arg mount options Theodore Ts'o
2010-03-02 18:18 ` [PATCH 03/28] ext4: Add block validity check when truncating indirect block mapped inodes Theodore Ts'o
2010-03-02 18:18 ` [PATCH 04/28] ext4: Add new tracepoint for jbd2_cleanup_journal_tail Theodore Ts'o
2010-03-02 18:18 ` [PATCH 05/28] ext4: Add new tracepoints to debug delayed allocation space functions Theodore Ts'o
2010-03-02 18:18 ` [PATCH 06/28] ext4: Use slab allocator for sub-page sized allocations Theodore Ts'o
2010-03-02 18:18 ` [PATCH 07/28] ext4: Use bitops to read/modify EXT4_I(inode)->i_state Theodore Ts'o
2010-03-02 18:18 ` [PATCH 08/28] ext4: Reserve INCOMPAT_EA_INODE and INCOMPAT_DIRDATA feature codepoints Theodore Ts'o
2010-03-02 18:18 ` [PATCH 09/28] ext4: move __func__ into a macro for ext4_warning, ext4_error Theodore Ts'o
2010-03-02 18:18 ` [PATCH 10/28] ext4: add missing error checking to ext4_expand_extra_isize_ea() Theodore Ts'o
2010-03-02 18:18 ` [PATCH 11/28] ext4: correctly calculate number of blocks for fiemap Theodore Ts'o
2010-03-03 7:47 ` Akira Fujita
2010-03-03 8:34 ` Leonard Michlmayr
2010-03-03 17:52 ` tytso
2010-03-04 5:40 ` Akira Fujita
2010-03-04 21:44 ` Leonard Michlmayr
2010-03-04 22:28 ` [incomplete PATCH] ext4: avoid overflow in fiemap Leonard Michlmayr
2010-03-07 3:38 ` tytso
2010-03-04 23:38 ` Eric Sandeen [this message]
2010-03-05 16:46 ` [PATCH 11/28] ext4: correctly calculate number of blocks for fiemap Leonard Michlmayr
2010-03-04 22:08 ` tytso
2010-03-04 23:47 ` Eric Sandeen
2010-03-02 18:18 ` [PATCH 12/28] jbd2: delay discarding buffers in journal_unmap_buffer Theodore Ts'o
2010-03-02 18:18 ` [PATCH 13/28] ext4: Fix BUG_ON at fs/buffer.c:652 in no journal mode Theodore Ts'o
2010-03-02 18:18 ` [PATCH 14/28] ext4: Add flag to files with blocks intentionally past EOF Theodore Ts'o
2010-03-02 18:18 ` [PATCH 15/28] ext4: mount flags manipulation cleanup Theodore Ts'o
2010-03-02 18:18 ` [PATCH 16/28] ext4: trivial quota cleanup Theodore Ts'o
2010-03-02 18:18 ` [PATCH 17/28] jbd2: clean up an assertion in jbd2_journal_commit_transaction() Theodore Ts'o
2010-03-02 18:18 ` [PATCH 18/28] ext4: Fix fencepost error in chosing choosing group vs file preallocation Theodore Ts'o
2010-03-02 18:18 ` [PATCH 19/28] ext4: deprecate obsoleted mount options Theodore Ts'o
2010-03-02 18:18 ` [PATCH 20/28] ext4: fix error handling in migrate Theodore Ts'o
2010-03-02 18:18 ` [PATCH 21/28] ext4: explicitly remove inode from orphan list after failed direct io Theodore Ts'o
2010-03-02 18:18 ` [PATCH 22/28] ext4: Handle non empty on-disk orphan link Theodore Ts'o
2010-03-02 18:18 ` [PATCH 23/28] ext4: make "offset" consistent in ext4_check_dir_entry() Theodore Ts'o
2010-03-02 18:18 ` [PATCH 24/28] ext4: mechanical change on dio get_block code in prepare for it to be used by buffer write Theodore Ts'o
2010-03-02 18:18 ` [PATCH 25/28] ext4: use ext4_get_block_write in " Theodore Ts'o
2010-03-02 18:18 ` [PATCH 26/28] ext4: Use direct_IO_no_locking in ext4 dio read Theodore Ts'o
2010-03-02 18:18 ` [PATCH 27/28] ext4: Convert BUG_ON checks to use ext4_error() instead Theodore Ts'o
2010-03-06 13:03 ` Aneesh Kumar K. V
2010-03-07 2:45 ` tytso
2010-03-07 5:51 ` Eric Sandeen
2010-03-07 17:36 ` Andreas Dilger
2010-03-08 17:46 ` Frank Mayhar
2010-03-02 18:18 ` [PATCH 28/28] ext4: Fix ext4_quota_write cross block boundary behaviour Theodore Ts'o
2010-03-02 18:26 ` [PATCH 00/28] Ext4 patch queue for the 2.6.34 merge window tytso
-- strict thread matches above, loose matches on Subject: below --
2010-03-05 5:57 [PATCH 11/28] ext4: correctly calculate number of blocks for fiemap Akira Fujita
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