Hi Joseph, On 09/14/2016 04:25 PM, Joseph Qi wrote: > Hi Eric, > Sorry for the delayed response. > I have got your explanation. So we have to unlock the page only in case > of retry, right? > If so, I think the unlock should be right before "goto try_again". No, the mmapped page should be unlocked as long as we cannot return VM_FAULT_LOCKED to do_page_mkpage(). Otherwise, the deadlock will happen in do_page_mkpage(). Please see the recent 2 mails;-)
Eric > > Thanks, > Joseph > > On 2016/9/14 16:04, Eric Ren wrote: >> Hi Joseph, >>>>> In ocfs2_write_begin_nolock(), we first grab the pages and then >>>>> allocate disk space for this write; ocfs2_try_to_free_truncate_log() >>>>> will be called if ENOSPC is turned; if we're lucky to get enough clusters, >>>>> which is usually the case, we start over again. But in >>>>> ocfs2_free_write_ctxt() >>>>> the target page isn't unlocked, so we will deadlock when trying to grab >>>>> the target page again. >>>> IMO, in ocfs2_grab_pages_for_write, mmap_page is mapping to w_pages and >>>> w_target_locked is set to true, and then will be unlocked by >>>> ocfs2_unlock_pages in ocfs2_free_write_ctxt. >>>> So I'm not getting the case "page isn't unlock". Could you please explain >>>> it in more detail? >>> Thanks for review;-) Follow up the calling chain: >>> >>> ocfs2_free_write_ctxt() >>> ->ocfs2_unlock_pages() >>> >>> in ocfs2_unlock_pages >>> (https://github.com/torvalds/linux/blob/master/fs/ocfs2/aops.c#L793), we >>> can see the code just put_page(target_page), but not unlock it. >> Did this answer your question? >> >> Thanks, >> Eric >>> Yeah, I will think this a bit more like: >>> why not unlock the target_page there? Is there other potential problems if >>> the "ret" is not "-ENOSPC" but >>> other possible error code? >>> >>> Thanks, >>> Eric >>> >>>> Thanks, >>>> Joseph >>>> >>>>> Fix this issue by unlocking the target page after we fail to allocate >>>>> enough space at the first time. >>>>> >>>>> Jan Kara helps me clear out the JBD2 part, and suggest the hint for root >>>>> cause. >>>>> >>>>> Signed-off-by: Eric Ren <z...@suse.com> >>>>> --- >>>>> fs/ocfs2/aops.c | 7 +++++++ >>>>> 1 file changed, 7 insertions(+) >>>>> >>>>> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c >>>>> index 98d3654..78d1d67 100644 >>>>> --- a/fs/ocfs2/aops.c >>>>> +++ b/fs/ocfs2/aops.c >>>>> @@ -1860,6 +1860,13 @@ out: >>>>> */ >>>>> try_free = 0; >>>>> + /* >>>>> + * Unlock mmap_page because the page has been locked when we >>>>> + * are here. >>>>> + */ >>>>> + if (mmap_page) >>>>> + unlock_page(mmap_page); >>>>> + >>>>> ret1 = ocfs2_try_to_free_truncate_log(osb, clusters_need); >>>>> if (ret1 == 1) >>>>> goto try_again; >>>>> >>>> >>> >>> >>> >>> _______________________________________________ >>> Ocfs2-devel mailing list >>> Ocfs2-devel@oss.oracle.com >>> https://oss.oracle.com/mailman/listinfo/ocfs2-devel >> > > _______________________________________________ Ocfs2-devel mailing list Ocfs2-devel@oss.oracle.com https://oss.oracle.com/mailman/listinfo/ocfs2-devel