GFS2: Fix "truncate in progress" hang

Following on from the recent clean up of gfs2_quotad, this patch moves
the processing of "truncate in progress" inodes from the glock workqueue
into gfs2_quotad. This fixes a hang due to the "truncate in progress"
processing requiring glocks in order to complete.

It might seem odd to use gfs2_quotad for this particular item, but
we have to use a pre-existing thread since creating a thread implies
a GFP_KERNEL memory allocation which is not allowed from the glock
workqueue context. Of the existing threads, gfs2_logd and gfs2_recoverd
may deadlock if used for this operation. gfs2_scand and gfs2_glockd are
both scheduled for removal at some (hopefully not too distant) future
point. That leaves only gfs2_quotad whose workload is generally fairly
light and is easily adapted for this extra task.

Also, as a result of this change, it opens the way for a future patch to
make the reading of the inode's information asynchronous with respect to
the glock workqueue, which is another improvement that has been on the list
for some time now.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index cfebc1793574..dd7d0f8f3575 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -244,6 +244,7 @@ struct gfs2_inode {
         struct gfs2_alloc *i_alloc;
         u64 i_goal;     /* goal block for allocations */
         struct rw_semaphore i_rw_mutex;
+        struct list_head i_trunc_list;
         u32 i_entries;
         u32 i_diskflags;
         u8 i_height;
@@ -550,6 +551,8 @@ struct gfs2_sbd {
         spinlock_t sd_quota_spin;
         struct mutex sd_quota_mutex;
         wait_queue_head_t sd_quota_wait;
+        struct list_head sd_trunc_list;
+        spinlock_t sd_trunc_lock;
 
         unsigned int sd_quota_slots;
         unsigned int sd_quota_chunks;