btrfs: fix search key advancing condition

The search key advancing condition used in copy_to_sk() is loose. It can
advance the key even if it reaches sk->max_*: e.g. when the max key = (512,
1024, -1) and the current key = (512, 1025, 10), it increments the
offset by 1, continues hopeless search from (512, 1025, 11). This issue
make ioctl() to take unexpectedly long time scanning all the leaf a blocks
one by one.

This commit fix the problem using standard way of key comparison:
btrfs_comp_cpu_keys()

Signed-off-by: Naohiro Aota <naota@elisp.net>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 0770c91586ca694e1f9c142fb653cf02c02dd686..3e2a80433504ca7f20c68bd05dcf73e8c45a687a 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1933,6 +1933,7 @@ static noinline int copy_to_sk(struct btrfs_root *root,
        u64 found_transid;
        struct extent_buffer *leaf;
        struct btrfs_ioctl_search_header sh;
+       struct btrfs_key test;
        unsigned long item_off;
        unsigned long item_len;
        int nritems;
@@ -2016,12 +2017,17 @@ static noinline int copy_to_sk(struct btrfs_root *root,
        }
 advance_key:
        ret = 0;
-       if (key->offset < (u64)-1 && key->offset < sk->max_offset)
+       test.objectid = sk->max_objectid;
+       test.type = sk->max_type;
+       test.offset = sk->max_offset;
+       if (btrfs_comp_cpu_keys(key, &test) >= 0)
+               ret = 1;
+       else if (key->offset < (u64)-1)
                key->offset++;
-       else if (key->type < (u8)-1 && key->type < sk->max_type) {
+       else if (key->type < (u8)-1) {
                key->offset = 0;
                key->type++;
-       } else if (key->objectid < (u64)-1 && key->objectid < sk->max_objectid) {
+       } else if (key->objectid < (u64)-1) {
                key->offset = 0;
                key->type = 0;
                key->objectid++;