From afce772e87c36c7f07f230a76d525025aaf09e41 Mon Sep 17 00:00:00 2001 From: Lu Fengqi Date: Mon, 13 Jun 2016 09:36:46 +0800 Subject: btrfs: fix check_shared for fiemap ioctl Only in the case of different root_id or different object_id, check_shared identified extent as the shared. However, If a extent was referred by different offset of same file, it should also be identified as shared. In addition, check_shared's loop scale is at least n^3, so if a extent has too many references, even causes soft hang up. First, add all delayed_ref to the ref_tree and calculate the unqiue_refs, if the unique_refs is greater than one, return BACKREF_FOUND_SHARED. Then individually add the on-disk reference(inline/keyed) to the ref_tree and calculate the unique_refs of the ref_tree to check if the unique_refs is greater than one.Because once there are two references to return SHARED, so the time complexity is close to the constant. Reported-by: Tsutomu Itoh Signed-off-by: Lu Fengqi Signed-off-by: David Sterba --- fs/btrfs/extent_io.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) (limited to 'fs/btrfs/extent_io.c') diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 44fe66b53c8b..8644df8ba527 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -20,6 +20,7 @@ #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; @@ -4487,11 +4488,24 @@ 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 @@ -4499,9 +4513,11 @@ 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(NULL, root->fs_info, + ret = btrfs_check_shared(trans, root->fs_info, root->objectid, btrfs_ino(inode), bytenr); + if (trans) + btrfs_end_transaction(trans, root); if (ret < 0) goto out_free; if (ret) -- cgit v1.2.3