Am Montag 05 Oktober 2009 21:30:39 schrieb Josef Bacik: > Like the cluster allocating stuff, we can lockup the box with the normal > allocation path. This happens when we > > 1) Start to cache a block group that is severely fragmented, but has a > decent amount of free space. > 2) Start to commit a transaction > 3) Have the commit try and empty out some of the delalloc inodes with > extents that are relatively large. > > The inodes will not be able to make the allocations because they will ask > for allocations larger than a contiguous area in the free space cache. So > we will wait for more progress to be made on the block group, but since > we're in a commit the caching kthread won't make any more progress and it > already has enough free space that wait_block_group_cache_progress will > just return. So, if we wait and fail to make the allocation the next time > around, just loop and go to the next block group. This keeps us from > getting stuck in a softlockup. Thanks, > > Signed-off-by: Josef Bacik <jba...@redhat.com> > --- > fs/btrfs/extent-tree.c | 23 +++++++++++++++++------ > 1 files changed, 17 insertions(+), 6 deletions(-) > > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c > index b259db3..e46b0b9 100644 > --- a/fs/btrfs/extent-tree.c > +++ b/fs/btrfs/extent-tree.c > @@ -3816,6 +3816,7 @@ static noinline int find_free_extent(struct > btrfs_trans_handle *trans, int loop = 0; > bool found_uncached_bg = false; > bool failed_cluster_refill = false; > + bool failed_alloc = false; > > WARN_ON(num_bytes < root->sectorsize); > btrfs_set_key_type(ins, BTRFS_EXTENT_ITEM_KEY); > @@ -4020,14 +4021,23 @@ refill_cluster: > > offset = btrfs_find_space_for_alloc(block_group, search_start, > num_bytes, empty_size); > - if (!offset && (cached || (!cached && > - loop == LOOP_CACHING_NOWAIT))) { > - goto loop; > - } else if (!offset && (!cached && > - loop > LOOP_CACHING_NOWAIT)) { > + /* > + * If we didn't find a chunk, and we haven't failed on this > + * block group before, and this block group is in the middle of > + * caching and we are ok with waiting, then go ahead and wait > + * for progress to be made, and set failed_alloc to true. > + * > + * If failed_alloc is true then we've already waited on this > + * block group once and should move on to the next block group. > + */ > + if (!offset && !failed_alloc && !cached && > + loop > LOOP_CACHING_NOWAIT) { > wait_block_group_cache_progress(block_group, > - num_bytes + empty_size); > + num_bytes + empty_size); > + failed_alloc = true; > goto have_block_group; > + } else if (!offset) { > + goto loop; > } > checks: > search_start = stripe_align(root, offset); > @@ -4075,6 +4085,7 @@ checks: > break; > loop: > failed_cluster_refill = false; > + failed_alloc = false; > btrfs_put_block_group(block_group); > } > up_read(&space_info->groups_sem); >
My box survived 6h of dbench with this patch whereas without it hangs within the first thwo minutes. Johannes -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html