On Mon, 5 Dec 2011, Allison Henderson wrote: > On 12/05/2011 04:38 PM, Hugh Dickins wrote: > > > > This has been outstanding for a month now, and we've heard no progress: > > please revert commit 02fac1297eb3 "ext4: fix partial page writes" for rc5. > > > > The problems appear on a 1k-blocksize filesystem under memory pressure: > > the hunk in ext4_da_write_end() causes oops, because it's playing with > > a page after generic_write_end() dropped our last reference to it; and > > backing out the hunk in ext4_da_write_begin() is then found to stop > > rare data corruption seen when kbuilding. > > > > Although I earlier reported that backing out the patch caused an fsx > > test to fail earlier, I've since found great variation in how soon it > > fails, and seen it fail just as quickly with 02fac1297eb3 still in. > > I also reported that I had to go back to 2.6.38 for fsx not to fail > > under memory pressure: you won't be surprised that that turned out to > > be because 2.6.38 defaults nomblk_io_submit but 2.6.39 mblk_io_submit. > > Have you tried Yongqiang's patch "[PATCH 1/2] ext4: let mpage_submit_io > works well when blocksize < pagesize" ? I have tried it and it does seem to > help, but I am still running into some failures that I am trying to debug, > but let please let us know if it helps the issues that you are seeing. Thx! That 1/2, or the 2/2 "ext4: let ext4_discard_partial_buffers handle pages without buffers correctly"? The latter is mostly a reversion of your 02fac1297eb3, so that's the one I need to fix the oops and rare data corruption. Perhaps you're suggesting 1/2 for fsx failures under memory pressure? I've now tried the fsx test on three machines, with both 1/2 and 2/2 applied to 3.2-rc4. On one machine, with ext2 on loop on tmpfs, the fsx test failed in a couple of minutes with those patches; on another machine, with ext2 on loop on tmpfs, it failed after about 40 minutes with the patches; on this laptop, with ext2 on SSD, it's just now failed after 35 minutes with the patches. That's not to say that Yongqiang's patches aren't good; but I cannot detect whether they make any improvement or not, since lasting for 2 or 40 minutes is typical for fsx under memory pressure with recent kernels. Hugh -- 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
