Ping? Maybe just a one-line reply isn't THAT difficult? 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... Thanks, /mjt 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@xxxxxxxxxx> >> 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@xxxxxxxxxx> >> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx> >> Cc: stable@xxxxxxxxxx >> >> >> 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@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
