From bb739cf08e8f32ea0b4a6d2ae22466488182c2fe Mon Sep 17 00:00:00 2001 From: Edmund Nadolski Date: Wed, 28 Jun 2017 21:56:58 -0600 Subject: [PATCH] btrfs: btrfs_check_shared should manage its own transaction Commit afce772e87c3 ("btrfs: fix check_shared for fiemap ioctl") added transaction semantics around calls to btrfs_check_shared() in order to provide accurate accounting of delayed refs. The transaction management should be done inside btrfs_check_shared(), so that callers do not need to manage transactions individually. Signed-off-by: Edmund Nadolski Signed-off-by: Jeff Mahoney Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/backref.c | 30 +++++++++++++++++++----------- fs/btrfs/backref.h | 4 +--- fs/btrfs/extent_io.c | 22 +++------------------- 3 files changed, 23 insertions(+), 33 deletions(-) diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c index 3725277f6e08..35cfa388dc0b 100644 --- a/fs/btrfs/backref.c +++ b/fs/btrfs/backref.c @@ -1580,20 +1580,21 @@ int btrfs_find_all_roots(struct btrfs_trans_handle *trans, /** * btrfs_check_shared - tell us whether an extent is shared * - * @trans: optional trans handle - * * btrfs_check_shared uses the backref walking code but will short * circuit as soon as it finds a root or inode that doesn't match the * one passed in. This provides a significant performance benefit for * callers (such as fiemap) which want to know whether the extent is * shared but do not need a ref count. * + * This attempts to allocate a transaction in order to account for + * delayed refs, but continues on even when the alloc fails. + * * Return: 0 if extent is not shared, 1 if it is shared, < 0 on error. */ -int btrfs_check_shared(struct btrfs_trans_handle *trans, - struct btrfs_fs_info *fs_info, u64 root_objectid, - u64 inum, u64 bytenr) +int btrfs_check_shared(struct btrfs_root *root, u64 inum, u64 bytenr) { + struct btrfs_fs_info *fs_info = root->fs_info; + struct btrfs_trans_handle *trans; struct ulist *tmp = NULL; struct ulist *roots = NULL; struct ulist_iterator uiter; @@ -1609,14 +1610,18 @@ int btrfs_check_shared(struct btrfs_trans_handle *trans, return -ENOMEM; } - if (trans) - btrfs_get_tree_mod_seq(fs_info, &elem); - else + trans = btrfs_join_transaction(root); + if (IS_ERR(trans)) { + trans = NULL; down_read(&fs_info->commit_root_sem); + } else { + btrfs_get_tree_mod_seq(fs_info, &elem); + } + ULIST_ITER_INIT(&uiter); while (1) { ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, tmp, - roots, NULL, root_objectid, inum, 1); + roots, NULL, root->objectid, inum, 1); if (ret == BACKREF_FOUND_SHARED) { /* this is the only condition under which we return 1 */ ret = 1; @@ -1631,10 +1636,13 @@ int btrfs_check_shared(struct btrfs_trans_handle *trans, bytenr = node->val; cond_resched(); } - if (trans) + + if (trans) { btrfs_put_tree_mod_seq(fs_info, &elem); - else + btrfs_end_transaction(trans); + } else { up_read(&fs_info->commit_root_sem); + } ulist_free(tmp); ulist_free(roots); return ret; diff --git a/fs/btrfs/backref.h b/fs/btrfs/backref.h index 9c41fbac3009..f9428aaaa77a 100644 --- a/fs/btrfs/backref.h +++ b/fs/btrfs/backref.h @@ -68,9 +68,7 @@ int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid, u64 start_off, struct btrfs_path *path, struct btrfs_inode_extref **ret_extref, u64 *found_off); -int btrfs_check_shared(struct btrfs_trans_handle *trans, - struct btrfs_fs_info *fs_info, u64 root_objectid, - u64 inum, u64 bytenr); +int btrfs_check_shared(struct btrfs_root *root, u64 inum, u64 bytenr); int __init btrfs_prelim_ref_init(void); void btrfs_prelim_ref_exit(void); diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index d6f761b4fae0..7dd1b2dc7c68 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -20,7 +20,6 @@ #include "locking.h" #include "rcu-string.h" #include "backref.h" -#include "transaction.h" static struct kmem_cache *extent_state_cache; static struct kmem_cache *extent_buffer_cache; @@ -4606,24 +4605,11 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, flags |= (FIEMAP_EXTENT_DELALLOC | FIEMAP_EXTENT_UNKNOWN); } else if (fieinfo->fi_extents_max) { - struct btrfs_trans_handle *trans; - u64 bytenr = em->block_start - (em->start - em->orig_start); disko = em->block_start + offset_in_extent; - /* - * We need a trans handle to get delayed refs - */ - trans = btrfs_join_transaction(root); - /* - * It's OK if we can't start a trans we can still check - * from commit_root - */ - if (IS_ERR(trans)) - trans = NULL; - /* * As btrfs supports shared space, this information * can be exported to userspace tools via @@ -4631,11 +4617,9 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, * then we're just getting a count and we can skip the * lookup stuff. */ - ret = btrfs_check_shared(trans, root->fs_info, - root->objectid, - btrfs_ino(BTRFS_I(inode)), bytenr); - if (trans) - btrfs_end_transaction(trans); + ret = btrfs_check_shared(root, + btrfs_ino(BTRFS_I(inode)), + bytenr); if (ret < 0) goto out_free; if (ret)