From b9fab919b748c7b39c19ff236ed6c5682c266dde Mon Sep 17 00:00:00 2001 From: Chris Mason Date: Sun, 6 May 2012 07:23:47 -0400 Subject: [PATCH] Btrfs: avoid sleeping in verify_parent_transid while atomic verify_parent_transid needs to lock the extent range to make sure no IO is underway, and so it can safely clear the uptodate bits if our checks fail. But, a few callers are using it with spinlocks held. Most of the time, the generation numbers are going to match, and we don't want to switch to a blocking lock just for the error case. This adds an atomic flag to verify_parent_transid, and changes it to return EAGAIN if it needs to block to properly verifiy things. Signed-off-by: Chris Mason --- fs/btrfs/ctree.c | 26 +++++++++++++++++--------- fs/btrfs/disk-io.c | 18 +++++++++++++----- fs/btrfs/disk-io.h | 3 ++- fs/btrfs/extent-tree.c | 2 +- fs/btrfs/tree-log.c | 2 +- 5 files changed, 34 insertions(+), 17 deletions(-) diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index 086303b9be64..4106264fbc65 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -725,7 +725,7 @@ int btrfs_realloc_node(struct btrfs_trans_handle *trans, cur = btrfs_find_tree_block(root, blocknr, blocksize); if (cur) - uptodate = btrfs_buffer_uptodate(cur, gen); + uptodate = btrfs_buffer_uptodate(cur, gen, 0); else uptodate = 0; if (!cur || !uptodate) { @@ -1360,7 +1360,12 @@ static noinline int reada_for_balance(struct btrfs_root *root, block1 = btrfs_node_blockptr(parent, slot - 1); gen = btrfs_node_ptr_generation(parent, slot - 1); eb = btrfs_find_tree_block(root, block1, blocksize); - if (eb && btrfs_buffer_uptodate(eb, gen)) + /* + * if we get -eagain from btrfs_buffer_uptodate, we + * don't want to return eagain here. That will loop + * forever + */ + if (eb && btrfs_buffer_uptodate(eb, gen, 1) != 0) block1 = 0; free_extent_buffer(eb); } @@ -1368,7 +1373,7 @@ static noinline int reada_for_balance(struct btrfs_root *root, block2 = btrfs_node_blockptr(parent, slot + 1); gen = btrfs_node_ptr_generation(parent, slot + 1); eb = btrfs_find_tree_block(root, block2, blocksize); - if (eb && btrfs_buffer_uptodate(eb, gen)) + if (eb && btrfs_buffer_uptodate(eb, gen, 1) != 0) block2 = 0; free_extent_buffer(eb); } @@ -1506,8 +1511,9 @@ read_block_for_search(struct btrfs_trans_handle *trans, tmp = btrfs_find_tree_block(root, blocknr, blocksize); if (tmp) { - if (btrfs_buffer_uptodate(tmp, 0)) { - if (btrfs_buffer_uptodate(tmp, gen)) { + /* first we do an atomic uptodate check */ + if (btrfs_buffer_uptodate(tmp, 0, 1) > 0) { + if (btrfs_buffer_uptodate(tmp, gen, 1) > 0) { /* * we found an up to date block without * sleeping, return @@ -1525,8 +1531,9 @@ read_block_for_search(struct btrfs_trans_handle *trans, free_extent_buffer(tmp); btrfs_set_path_blocking(p); + /* now we're allowed to do a blocking uptodate check */ tmp = read_tree_block(root, blocknr, blocksize, gen); - if (tmp && btrfs_buffer_uptodate(tmp, gen)) { + if (tmp && btrfs_buffer_uptodate(tmp, gen, 0) > 0) { *eb_ret = tmp; return 0; } @@ -1561,7 +1568,7 @@ read_block_for_search(struct btrfs_trans_handle *trans, * and give up so that our caller doesn't loop forever * on our EAGAINs. */ - if (!btrfs_buffer_uptodate(tmp, 0)) + if (!btrfs_buffer_uptodate(tmp, 0, 0)) ret = -EIO; free_extent_buffer(tmp); } @@ -4045,7 +4052,7 @@ again: tmp = btrfs_find_tree_block(root, blockptr, btrfs_level_size(root, level - 1)); - if (tmp && btrfs_buffer_uptodate(tmp, gen)) { + if (tmp && btrfs_buffer_uptodate(tmp, gen, 1) > 0) { free_extent_buffer(tmp); break; } @@ -4168,7 +4175,8 @@ next: struct extent_buffer *cur; cur = btrfs_find_tree_block(root, blockptr, btrfs_level_size(root, level - 1)); - if (!cur || !btrfs_buffer_uptodate(cur, gen)) { + if (!cur || + btrfs_buffer_uptodate(cur, gen, 1) <= 0) { slot++; if (cur) free_extent_buffer(cur); diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index d0c969beaad4..a7ffc88a7dbe 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -323,7 +323,8 @@ static int csum_tree_block(struct btrfs_root *root, struct extent_buffer *buf, * in the wrong place. */ static int verify_parent_transid(struct extent_io_tree *io_tree, - struct extent_buffer *eb, u64 parent_transid) + struct extent_buffer *eb, u64 parent_transid, + int atomic) { struct extent_state *cached_state = NULL; int ret; @@ -331,6 +332,9 @@ static int verify_parent_transid(struct extent_io_tree *io_tree, if (!parent_transid || btrfs_header_generation(eb) == parent_transid) return 0; + if (atomic) + return -EAGAIN; + lock_extent_bits(io_tree, eb->start, eb->start + eb->len - 1, 0, &cached_state); if (extent_buffer_uptodate(eb) && @@ -372,7 +376,8 @@ static int btree_read_extent_buffer_pages(struct btrfs_root *root, ret = read_extent_buffer_pages(io_tree, eb, start, WAIT_COMPLETE, btree_get_extent, mirror_num); - if (!ret && !verify_parent_transid(io_tree, eb, parent_transid)) + if (!ret && !verify_parent_transid(io_tree, eb, + parent_transid, 0)) break; /* @@ -1202,7 +1207,7 @@ static int __must_check find_and_setup_root(struct btrfs_root *tree_root, root->commit_root = NULL; root->node = read_tree_block(root, btrfs_root_bytenr(&root->root_item), blocksize, generation); - if (!root->node || !btrfs_buffer_uptodate(root->node, generation)) { + if (!root->node || !btrfs_buffer_uptodate(root->node, generation, 0)) { free_extent_buffer(root->node); root->node = NULL; return -EIO; @@ -3143,7 +3148,8 @@ int close_ctree(struct btrfs_root *root) return 0; } -int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid) +int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid, + int atomic) { int ret; struct inode *btree_inode = buf->pages[0]->mapping->host; @@ -3153,7 +3159,9 @@ int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid) return ret; ret = verify_parent_transid(&BTRFS_I(btree_inode)->io_tree, buf, - parent_transid); + parent_transid, atomic); + if (ret == -EAGAIN) + return ret; return !ret; } diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h index a7ace1a2dd12..ab1830aaf0ed 100644 --- a/fs/btrfs/disk-io.h +++ b/fs/btrfs/disk-io.h @@ -66,7 +66,8 @@ void btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr); void __btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr); void btrfs_free_fs_root(struct btrfs_fs_info *fs_info, struct btrfs_root *root); void btrfs_mark_buffer_dirty(struct extent_buffer *buf); -int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid); +int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid, + int atomic); int btrfs_set_buffer_uptodate(struct extent_buffer *buf); int btrfs_read_buffer(struct extent_buffer *buf, u64 parent_transid); u32 btrfs_csum_data(struct btrfs_root *root, char *data, u32 seed, size_t len); diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 6fc2e6f5aab8..49fd7b66d57b 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -6568,7 +6568,7 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans, goto skip; } - if (!btrfs_buffer_uptodate(next, generation)) { + if (!btrfs_buffer_uptodate(next, generation, 0)) { btrfs_tree_unlock(next); free_extent_buffer(next); next = NULL; diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c index d017283ae6f5..eb1ae908582c 100644 --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -279,7 +279,7 @@ static int process_one_buffer(struct btrfs_root *log, log->fs_info->extent_root, eb->start, eb->len); - if (btrfs_buffer_uptodate(eb, gen)) { + if (btrfs_buffer_uptodate(eb, gen, 0)) { if (wc->write) btrfs_write_tree_block(eb); if (wc->wait) -- 2.39.2