From: Josef Bacik josef@toxicpanda.com
commit 9c343784c4328781129bcf9e671645f69fe4b38a upstream.
Nikolay noticed a bunch of test failures with my global rsv steal patches. At first he thought they were introduced by them, but they've been failing for a while with 64k nodes.
The problem is with 64k nodes we have a global reserve that calculates out to 13MiB on a freshly made file system, which only has 8MiB of metadata space. Because of changes I previously made we no longer account for the global reserve in the overcommit logic, which means we correctly allow overcommit to happen even though we are already overcommitted.
However in some corner cases, for example btrfs/170, we will allocate the entire file system up with data chunks before we have enough space pressure to allocate a metadata chunk. Then once the fs is full we ENOSPC out because we cannot overcommit and the global reserve is taking up all of the available space.
The most ideal way to deal with this is to change our space reservation stuff to take into account the height of the tree's that we're modifying, so that our global reserve calculation does not end up so obscenely large.
However that is a huge undertaking. Instead fix this by forcing a chunk allocation if the global reserve is larger than the total metadata space. This gives us essentially the same behavior that happened before, we get a chunk allocated and these tests can pass.
This is meant to be a stop-gap measure until we can tackle the "tree height only" project.
Fixes: 0096420adb03 ("btrfs: do not account global reserve in can_overcommit") CC: stable@vger.kernel.org # 5.4+ Reviewed-by: Nikolay Borisov nborisov@suse.com Tested-by: Nikolay Borisov nborisov@suse.com Signed-off-by: Josef Bacik josef@toxicpanda.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/btrfs/block-rsv.c | 3 +++ fs/btrfs/transaction.c | 18 ++++++++++++++++++ 2 files changed, 21 insertions(+)
--- a/fs/btrfs/block-rsv.c +++ b/fs/btrfs/block-rsv.c @@ -5,6 +5,7 @@ #include "block-rsv.h" #include "space-info.h" #include "transaction.h" +#include "block-group.h"
/* * HOW DO BLOCK RESERVES WORK @@ -405,6 +406,8 @@ void btrfs_update_global_block_rsv(struc else block_rsv->full = 0;
+ if (block_rsv->size >= sinfo->total_bytes) + sinfo->force_alloc = CHUNK_ALLOC_FORCE; spin_unlock(&block_rsv->lock); spin_unlock(&sinfo->lock); } --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -21,6 +21,7 @@ #include "dev-replace.h" #include "qgroup.h" #include "block-group.h" +#include "space-info.h"
#define BTRFS_ROOT_TRANS_TAG 0
@@ -523,6 +524,7 @@ start_transaction(struct btrfs_root *roo u64 num_bytes = 0; u64 qgroup_reserved = 0; bool reloc_reserved = false; + bool do_chunk_alloc = false; int ret;
/* Send isn't supposed to start transactions. */ @@ -585,6 +587,9 @@ start_transaction(struct btrfs_root *roo delayed_refs_bytes); num_bytes -= delayed_refs_bytes; } + + if (rsv->space_info->force_alloc) + do_chunk_alloc = true; } else if (num_items == 0 && flush == BTRFS_RESERVE_FLUSH_ALL && !delayed_refs_rsv->full) { /* @@ -667,6 +672,19 @@ got_it: current->journal_info = h;
/* + * If the space_info is marked ALLOC_FORCE then we'll get upgraded to + * ALLOC_FORCE the first run through, and then we won't allocate for + * anybody else who races in later. We don't care about the return + * value here. + */ + if (do_chunk_alloc && num_bytes) { + u64 flags = h->block_rsv->space_info->flags; + + btrfs_chunk_alloc(h, btrfs_get_alloc_profile(fs_info, flags), + CHUNK_ALLOC_NO_FORCE); + } + + /* * btrfs_record_root_in_trans() needs to alloc new extents, and may * call btrfs_join_transaction() while we're also starting a * transaction.