All of lore.kernel.org
 help / color / mirror / Atom feed
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
> 
> 
> --
> 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


  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
2010-03-05  5:57 [PATCH 11/28] ext4: correctly calculate number of blocks for fiemap Akira Fujita

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=4B90448A.2030609@redhat.com \
    --to=sandeen@redhat.com \
    --cc=a-fujita@rs.jp.nec.com \
    --cc=leonard.michlmayr@gmail.com \
    --cc=linux-ext4@vger.kernel.org \
    --cc=tytso@mit.edu \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.