On Mon, Feb 28, 2011 at 11:13:59AM +0100, Johannes Hirte wrote: > On Monday 28 February 2011 02:46:05 Chris Mason wrote: > > Excerpts from Mitch Harder's message of 2011-02-25 13:43:37 -0500: > > > Some clarification on my previous message... > > > > > > After looking at my ftrace log more closely, I can see where Btrfs is > > > trying to release the allocated pages. However, the calculation for > > > the number of dirty_pages is equal to 1 when "copied == 0". > > > > > > So I'm seeing at least two problems: > > > (1) It keeps looping when "copied == 0". > > > (2) One dirty page is not being released on every loop even though > > > "copied == 0" (at least this problem keeps it from being an infinite > > > loop by eventually exhausting reserveable space on the disk). > > > > Hi everyone, > > > > There are actually tow bugs here. First the one that Mitch hit, and a > > second one that still results in bad file_write results with my > > debugging hunks (the first two hunks below) in place. > > > > My patch fixes Mitch's bug by checking for copied == 0 after > > btrfs_copy_from_user and going the correct delalloc accounting. This > > one looks solved, but you'll notice the patch is bigger. > > > > First, I add some random failures to btrfs_copy_from_user() by failing > > everyone once and a while. This was much more reliable than trying to > > use memory pressure than making copy_from_user fail. > > > > If copy_from_user fails and we partially update a page, we end up with a > > page that may go away due to memory pressure. But, btrfs_file_write > > assumes that only the first and last page may have good data that needs > > to be read off the disk. > > > > This patch ditches that code and puts it into prepare_pages instead. > > But I'm still having some errors during long stress.sh runs. Ideas are > > more than welcome, hopefully some other timezones will kick in ideas > > while I sleep. > > At least it doesn't fix the emerge-problem for me. The behavior is now the same > as with 2.6.38-rc3. It needs a 'emerge --oneshot dev-libs/libgcrypt' with no > further interaction to get the emerge-process hang with a svn-process > consuming 100% CPU. I can cancel the emerge-process with ctrl-c but the > spawned svn-process stays and it needs a reboot to get rid of it. Can you cat /proc/$pid/wchan a few times so we can get an idea of where it's looping? Thanks, Josef -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
