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Message-ID: <q2o87f94c371004091015ud3b91710o58f2ce050255084a@mail.gmail.com> Date: Fri, 9 Apr 2010 13:15:44 -0400 From: Greg Freemyer <greg.freemyer@...il.com> To: djwong@...ibm.com Cc: "Theodore Ts'o" <tytso@....edu>, linux-ext4 <linux-ext4@...r.kernel.org> Subject: Re: EXT4_IOC_MOVE_EXT file corruption! On Fri, Apr 9, 2010 at 12:20 PM, Darrick J. Wong <djwong@...ibm.com> wrote: > On Mon, Apr 05, 2010 at 03:02:20PM -0700, Darrick J. Wong wrote: >> Hi all, >> >> I wrote a program called e4frag that deliberately tries to fragment an ext4 >> filesystem via EXT4_IOC_MOVE_EXT so that I could run e4defrag through its >> paces. While running e4frag and e4defrag concurrently on a kernel source tree, >> I discovered ongoing file corruption. It appears that if e4frag and e4defrag >> hit the same file at same time, the file ends up with a 4K data block from >> somewhere else. "Somewhere else" seems to be a small chunk of binary gibberish >> followed by contents from other files(!) Obviously this isn't a good thing to > > It seems that if you mount the filesystem with -o sync this problem goes away. > > --D That implies to me that there is a missing block flush prior to a lock being released. That should not be too hard to find by code inspection. As conceptually interested as I am in ext4_ioc_move_ext, I have not really gone through the code with any detail. Maybe I'll contribute by doing that. Greg -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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