Messages in this thread | | | Subject | e2fsprogs bug [was Re: ext2/3 file limits to avoid overflowing i_blocks] | From | "Stephen C. Tweedie" <> | Date | Thu, 17 Mar 2005 17:39:51 +0000 |
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Hi,
On Thu, 2005-03-17 at 17:23, Stephen C. Tweedie wrote:
> I wrote a small program to calculate the total indirect tree overhead > for any given file size, and 0x1ff7fffe000 turned out to be the largest > file we can get without the total i_blocks overflowing 2^32. > > But in testing, that *just* wrapped --- we need to limit the file to be > one page smaller than that to deal with the possibility of an EA/ACL > block being accounted against i_blocks.
On a side, issue, e2fsck was unable to find any problem on that filesystem after the i_blocks had wrapped exactly to zero.
The bug seems to be in e2fsck/pass1.c: we do the numblocks checking inside process_block(), which is called as an inode block iteration function in check_blocks(). Then, later, check_blocks() does
if (inode->i_file_acl && check_ext_attr(ctx, pctx, block_buf)) pb.num_blocks++;
pb.num_blocks *= (fs->blocksize / 512);
but without any further testing to see if pb.num_blocks has exceeded the max_blocks. So by the time we've got to the end of check_blocks(), we're testing the wrapped i_blocks on disk against the wrapped num_blocks in memory, and so e2fsck fails to notice anything wrong.
The fix may be as simple as just moving the
if (inode->i_file_acl && check_ext_attr(ctx, pctx, block_buf)) pb.num_blocks++;
earlier in the function; Ted, do you see any problems with that?
--Stephen
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