On Sat 17-03-12 13:31:30, Michael Tokarev wrote: > 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... 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@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 -- 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
