forked from luck/tmp_suning_uos_patched
a81cb9a2d9
I've experienced filesystem freezes with permanent spikes in the active process count for quite a while, particularly on filesystems whose available raw space has already been fully allocated to chunks. While looking into this, I found a pretty obvious error in do_chunk_alloc: it sets space_info->chunk_alloc, but if btrfs_alloc_chunk returns an error other than ENOSPC, it returns leaving that flag set, which causes any other threads waiting for space_info->chunk_alloc to become zero to spin indefinitely. I haven't double-checked that this patch fixes the failure I've observed fully (it's not exactly trivial to trigger), but it surely is a bug and the fix is trivial, so... Please put it in :-) What I saw in that function also happens to explain why in some cases I see filesystems allocate a huge number of chunks that remain unused (leading to the scenario above, of not having more chunks to allocate). It happens for data and metadata, but not necessarily both. I'm guessing some thread sets the force_alloc flag on the corresponding space_info, and then several threads trying to get disk space end up attempting to allocate a new chunk concurrently. All of them will see the force_alloc flag and bump their local copy of force up to the level they see first, and they won't clear it even if another thread succeeds in allocating a chunk, thus clearing the force flag. Then each thread that observed the force flag will, on its turn, force the allocation of a new chunk. And any threads that come in while it does that will see the force flag still set and pick it up, and so on. This sounds like a problem to me, but... what should the correct behavior be? Clear force_flag once we copy it to a local force? Reset force to the incoming value on every loop? Set the flag to our incoming force if we have it at first, clear our local flag, and move it from the space_info when we determined that we are the thread that's going to perform the allocation? btrfs: clear chunk_alloc flag on retryable failure From: Alexandre Oliva <oliva@gnu.org> If btrfs_alloc_chunk fails with e.g. ENOMEM, we exit do_chunk_alloc without clearing chunk_alloc in space_info. As a result, any further calls to do_chunk_alloc on that filesystem will start busy-waiting for chunk_alloc to be cleared, but it never will be. This patch adjusts do_chunk_alloc so that it clears this flag in case of an error. Signed-off-by: Alexandre Oliva <oliva@gnu.org> Signed-off-by: Josef Bacik <jbacik@fusionio.com> |
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| .. | ||
| acl.c | ||
| async-thread.c | ||
| async-thread.h | ||
| backref.c | ||
| backref.h | ||
| btrfs_inode.h | ||
| check-integrity.c | ||
| check-integrity.h | ||
| compat.h | ||
| compression.c | ||
| compression.h | ||
| ctree.c | ||
| ctree.h | ||
| delayed-inode.c | ||
| delayed-inode.h | ||
| delayed-ref.c | ||
| delayed-ref.h | ||
| dev-replace.c | ||
| dev-replace.h | ||
| dir-item.c | ||
| disk-io.c | ||
| disk-io.h | ||
| export.c | ||
| export.h | ||
| extent_io.c | ||
| extent_io.h | ||
| extent_map.c | ||
| extent_map.h | ||
| extent-tree.c | ||
| file-item.c | ||
| file.c | ||
| free-space-cache.c | ||
| free-space-cache.h | ||
| hash.h | ||
| inode-item.c | ||
| inode-map.c | ||
| inode-map.h | ||
| inode.c | ||
| ioctl.c | ||
| Kconfig | ||
| locking.c | ||
| locking.h | ||
| lzo.c | ||
| Makefile | ||
| math.h | ||
| ordered-data.c | ||
| ordered-data.h | ||
| orphan.c | ||
| print-tree.c | ||
| print-tree.h | ||
| qgroup.c | ||
| raid56.c | ||
| raid56.h | ||
| rcu-string.h | ||
| reada.c | ||
| relocation.c | ||
| root-tree.c | ||
| scrub.c | ||
| send.c | ||
| send.h | ||
| struct-funcs.c | ||
| super.c | ||
| sysfs.c | ||
| transaction.c | ||
| transaction.h | ||
| tree-defrag.c | ||
| tree-log.c | ||
| tree-log.h | ||
| ulist.c | ||
| ulist.h | ||
| version.h | ||
| volumes.c | ||
| volumes.h | ||
| xattr.c | ||
| xattr.h | ||
| zlib.c | ||