On 4/19/12 8:10 AM, Jouko Orava wrote: > Hi Zheng, > > I can confirm the bug exists on latest RHEL 6 x86_64 kernels (2.6.32-220). > > On current mainline kernels all writes are limited to one page under 2GB, > which masks the problem. I have not checked if mainline 2.6.32 has this > limit or not. It does not matter: the limit is just a band-aid to paper > over filesystem bugs, and should not mean you don't fix filesystem bugs. FWIW, we tried fairly hard to get the limit lifted in the vfs, to no avail. > I can confirm the one line patch to fs/ext4/file.c does fix the problem. > I have test kernels based on 2.6.32-220.7.1.el6.x86_64 with only > the patch applied, at > http://www.helsinki.fi/~joorava/kernel/ > if anyone else is interested in testing. > > I did some (limited) testing on ext4 with the patch. It fixes the problem: > large writes work very well too. No problems popped up in testing. > > Tested-by: Jouko Orava <jouko.orava@xxxxxxxxxxx> > > > I'd also like to point at the real bug here, in Jouni's original strace: > > writev(3, [{"\0\0\0\0\0\0\0\0", 8}, {"", 2147483648}], 2) = -2147483640 > > The syscall returns a negative value, which is not the actual number of > bytes written (since it is 32-bit wrapped), and errno has not been > changed. There is no way for userspace to handle this result correctly! > > There is no way anyone sane should just gloss over this saying > "programmer fault, you're doing it wrong". > This is a real bug, and deserves fixing sooner rather than later. Agreed, I think Dave was a little to quick on the draw on his reply. :) -Eric > Thanks, > Jouko Orava > -- > 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
