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author | David S. Miller <davem@davemloft.net> | 2011-12-02 13:49:21 -0500 |
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committer | David S. Miller <davem@davemloft.net> | 2011-12-02 13:49:21 -0500 |
commit | b3613118eb30a589d971e4eccbbb2a1314f5dfd4 (patch) | |
tree | 868c1ee59e1b5c19a4f2e43716400d0001a994e5 /fs/btrfs/ctree.c | |
parent | 7505afe28c16a8d386624930a018d0052c75d687 (diff) | |
parent | 5983fe2b29df5885880d7fa3b91aca306c7564ef (diff) | |
download | op-kernel-dev-b3613118eb30a589d971e4eccbbb2a1314f5dfd4.zip op-kernel-dev-b3613118eb30a589d971e4eccbbb2a1314f5dfd4.tar.gz |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
Diffstat (limited to 'fs/btrfs/ctree.c')
-rw-r--r-- | fs/btrfs/ctree.c | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index 0fe615e..dede441 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -514,10 +514,25 @@ static inline int should_cow_block(struct btrfs_trans_handle *trans, struct btrfs_root *root, struct extent_buffer *buf) { + /* ensure we can see the force_cow */ + smp_rmb(); + + /* + * We do not need to cow a block if + * 1) this block is not created or changed in this transaction; + * 2) this block does not belong to TREE_RELOC tree; + * 3) the root is not forced COW. + * + * What is forced COW: + * when we create snapshot during commiting the transaction, + * after we've finished coping src root, we must COW the shared + * block to ensure the metadata consistency. + */ if (btrfs_header_generation(buf) == trans->transid && !btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN) && !(root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID && - btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC))) + btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC)) && + !root->force_cow) return 0; return 1; } |