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Date: Mon, 19 Mar 2012 10:10:11 -0700 From: Jiaying Zhang <jiayingz@...gle.com> To: Michael Tokarev <mjt@....msk.ru>, Theodore Tso <tytso@...gle.com> Cc: gregkh@...uxfoundation.org, stable@...nel.org, linux-ext4@...r.kernel.org, "Theodore Ts'o" <tytso@....edu>, Jan Kara <jack@...e.cz> Subject: Re: what happened with dccaf33fa37 "ext4: flush any pending end_io requests before DIO" for 3.0? On Mon, Mar 19, 2012 at 9:42 AM, Jan Kara <jack@...e.cz> wrote: > On Sat 17-03-12 13:31:30, Michael Tokarev wrote: >> Ping? >> >> Maybe just a one-line reply isn't THAT difficult? Sorry for the slow response. I am not sure what happened to this patch. Ted, do you know what we need to do to get this patch to the stable release? Jiaying >> >> We've a data corruption bug in current longterm stable kernel >> series which is known and has a fix and tagged for -stable for >> over half a year already... > Greg, any idea why this patch was not included? > > Honza > >> On 28.02.2012 15:42, Michael Tokarev wrote: >> > Is there something wrong with my question? I asked it 1.5 months ago... >> > >> > Meanwhile, we're using this patch on our database server since >> > Aug-2011, and it appears to work correctly - direct and buffered >> > I/O works together without surprizes. Without this patch, I see >> > unexpected results. >> > >> > Thanks, >> > >> > /mjt >> > >> > On 01.12.2011 00:38, Michael Tokarev wrote: >> >> Hello. >> >> >> >> Back in August 2011, a commit has been tagged to be included >> >> into stable, this one: >> >> >> >> commit dccaf33fa37a1bc5d651baeb3bfeb6becb86597b >> >> Author: Jiaying Zhang <jiayingz@...gle.com> >> >> Date: Fri Aug 19 19:13:32 2011 -0400 >> >> >> >> ext4: flush any pending end_io requests before DIO reads w/dioread_nolock >> >> >> >> There is a race between ext4 buffer write and direct_IO read with >> >> dioread_nolock mount option enabled. The problem is that we clear >> >> PageWriteback flag during end_io time but will do >> >> uninitialized-to-initialized extent conversion later with dioread_nolock. >> >> If an O_direct read request comes in during this period, ext4 will return >> >> zero instead of the recently written data. >> >> >> >> This patch checks whether there are any pending uninitialized-to-initialized >> >> extent conversion requests before doing O_direct read to close the race. >> >> Note that this is just a bandaid fix. The fundamental issue is that we >> >> clear PageWriteback flag before we really complete an IO, which is >> >> problem-prone. To fix the fundamental issue, we may need to implement an >> >> extent tree cache that we can use to look up pending to-be-converted extents. >> >> >> >> Signed-off-by: Jiaying Zhang <jiayingz@...gle.com> >> >> Signed-off-by: "Theodore Ts'o" <tytso@....edu> >> >> Cc: stable@...nel.org >> >> >> >> >> >> There was one more ext4 commit at that time, which made its way into >> >> stable but this one did not. >> >> >> >> I wonder if the reason for that was the fact that it needed a small >> >> "backport" for 3.0, since in 3.1+ the code has been moved into another >> >> file, and the context is slightly different. In that case, attached >> >> is the "backport" which we use with 3.0.x since that time. >> >> >> >> Thanks! >> >> >> >> /mjt >> > >> >> -- >> 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 -- 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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