On 10/7/07, Pekka J Enberg <penberg@xxxxxxxxxxxxxx> wrote: > On 10/7/07, Erez Zadok <ezk@xxxxxxxxxxxxx> wrote: > > Anyway, some Ubuntu users of Unionfs reported that msync(2) sometimes > > returns AOP_WRITEPAGE_ACTIVATE (decimal 524288) back to userland. > > Therefore, some user programs fail, esp. if they're written such as > > this: > ... > It's a kernel bug. AOP_WRITEPAGE_ACTIVATE is a hint to the VM to avoid > writeback of the page in the near future. I wonder if it's enough that we > change the return value to zero from > mm/page-writeback.c:write_cache_pages() in case we hit AOP_WRITEPAGE_ACTIVE... Doesn't appear to be enough. I can't figure out why (since it appears write_cache_pages bubbles up directly to sys_msync), but with that patch applied, in my test case[1], msync returns -1 EIO. However, with the exact same kernel without that patch applied, msync returns 524288 (AOP_WRITEPAGE_ACTIVATE). But as your patch specifically flips 524288 to 0, I can't figure out how it eventually returns -1 EIO. Ryan [1] "apt-get check" on a unionfs2 mount backed by tmpfs over cdrom, standard livecd setup - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
