From: Steven Whitehouse <swhiteho@redhat.com> Subject: [RHEL5.1] [GFS2] Fix bz 231380: GFS2 will hang if you run iozone on one node and do a du -h on another node Date: Thu, 05 Apr 2007 11:13:59 +0100 Bugzilla: 231380 Message-Id: <1175768039.1636.238.camel@quoit.chygwyn.com> Changelog: [GFS2] resolve deadlock when writing and accessing a file Hi, This patch (from Josef Whiter) fixes the problem that we have been having with deadlocks during unlocking a glock when there is a queued, pending demote request. Its already in the upstream kernel and has been verified to fix the bug. Steve. I'm not entirely sure if this is the best fix for this problem, so I'm open for suggetions. If we are writing a file, and in the middle of writing the file another node attempts to get a shared lock on that file (by doing a du for example) the process doing the writing will hang waiting on lock_page. The reason for this is because when we have waiters on a exclusive glock, we will go through and flush out all dirty pages associated with that inode and release the lock. The problem is that when we flush the dirty pages, we could hit a page that we have locked durring the generic_file_buffered_write part of this operation. This patch unlocks the page before we go to dequeue the lock and locks it immediatly afterwards, since generic_file_buffered_write needs the page locked when the commit_write is completed. This patch resolves the problem, however if somebody sees a better way to do this please don't hesistate to yell. Thank you, Josef Signed-off-by: Josef Whiter <jwhiter@redhat.com> --- gfs2-2.6-nmw/fs/gfs2/ops_address.c.josef 2007-03-08 15:04:10.000000000 -0500 +++ gfs2-2.6-nmw/fs/gfs2/ops_address.c 2007-03-12 17:23:24.000000000 -0400 @@ -507,7 +507,9 @@ gfs2_quota_unlock(ip); gfs2_alloc_put(ip); } + unlock_page(page); gfs2_glock_dq_m(1, &ip->i_gh); + lock_page(page); gfs2_holder_uninit(&ip->i_gh); return 0; @@ -520,7 +522,9 @@ gfs2_quota_unlock(ip); gfs2_alloc_put(ip); } + unlock_page(page); gfs2_glock_dq_m(1, &ip->i_gh); + lock_page(page); gfs2_holder_uninit(&ip->i_gh); fail_nounlock: ClearPageUptodate(page);