From: Wang Xiaoguang <wangxg.fnst@xxxxxxxxxxxxxx> In btrfs_delalloc_reserve_metadata(), the number of metadata bytes we try to reserve is calculated by the difference between outstanding_extents and reserved_extents. When reserve_metadata_bytes() fails to reserve desited metadata space, it has already done some reclaim work, such as write ordered extents. In that case, outstanding_extents and reserved_extents may already changed, and we may reserve enough metadata space then. So this patch will try to call reserve_metadata_bytes() at most 3 times to ensure we really run out of space. Such false ENOSPC is mainly caused by small file extents and time consuming delalloc functions, which mainly affects in-band de-duplication. (Compress should also be affected, but LZO/zlib is faster than SHA256, so still harder to trigger than dedupe). Signed-off-by: Wang Xiaoguang <wangxg.fnst@xxxxxxxxxxxxxx> --- fs/btrfs/extent-tree.c | 25 ++++++++++++++++++++++--- 1 file changed, 22 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index dabd721..016d2ec 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -2421,7 +2421,7 @@ static int run_one_delayed_ref(struct btrfs_trans_handle *trans, * a new extent is revered, then deleted * in one tran, and inc/dec get merged to 0. * - * In this case, we need to remove its dedup + * In this case, we need to remove its dedupe * hash. */ btrfs_dedupe_del(trans, fs_info, node->bytenr); @@ -5675,6 +5675,7 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes) bool delalloc_lock = true; u64 to_free = 0; unsigned dropped; + int loops = 0; /* If we are a free space inode we need to not flush since we will be in * the middle of a transaction commit. We also don't need the delalloc @@ -5690,11 +5691,12 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes) btrfs_transaction_in_commit(root->fs_info)) schedule_timeout(1); + num_bytes = ALIGN(num_bytes, root->sectorsize); + +again: if (delalloc_lock) mutex_lock(&BTRFS_I(inode)->delalloc_mutex); - num_bytes = ALIGN(num_bytes, root->sectorsize); - spin_lock(&BTRFS_I(inode)->lock); nr_extents = (unsigned)div64_u64(num_bytes + BTRFS_MAX_EXTENT_SIZE - 1, @@ -5815,6 +5817,23 @@ out_fail: } if (delalloc_lock) mutex_unlock(&BTRFS_I(inode)->delalloc_mutex); + /* + * The number of metadata bytes is calculated by the difference + * between outstanding_extents and reserved_extents. Sometimes though + * reserve_metadata_bytes() fails to reserve the wanted metadata bytes, + * indeed it has already done some work to reclaim metadata space, hence + * both outstanding_extents and reserved_extents would have changed and + * the bytes we try to reserve would also has changed(may be smaller). + * So here we try to reserve again. This is much useful for online + * dedupe, which will easily eat almost all meta space. + * + * XXX: Indeed here 3 is arbitrarily choosed, it's a good workaround for + * online dedupe, later we should find a better method to avoid dedupe + * enospc issue. + */ + if (unlikely(ret == -ENOSPC && loops++ < 3)) + goto again; + return ret; } -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
