LU-2901 mdt: duplicate link names in directory

When creating a hard link to a file, the MDT/MDD/OSD code does
not verify whether the target link name already exists in the
directory.  The ZFS ZAP code checks for duplicate entries. The
add_dirent_to_buf() function in ldiskfs only checks entries for
duplicates while it is traversing the leaf block looking for free
space.  Even if it scanned the whole leaf block, this would not
work for non-htree directories since there is no guarantee that
the name is being inserted into the same leaf block.

To fix this, link should check target object doesn't exist as
other creat operations.

Add sanity.sh test_31o with multiple threads racing to link a new
name into the directory, while ensuring that there is a free entry
in the leaf block that is large enough to hold the duplicate name.
This needs to be racy, because otherwise the client VFS will see
the existing name and not send the RPC to the MDS, hiding the bug.

Lustre-change: http://review.whamcloud.com/6591

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Lai Siyao <lai.siyao@intel.com>
Signed-off-by: Bob Glossman <bob.glossman@intel.com>
Signed-off-by: Jian Yu <jian.yu@intel.com>
Change-Id: Idb7976224b4860a1a07dac4d4467d67a93cda84f
Reviewed-on: http://review.whamcloud.com/6678
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>

diff --git a/lustre/mdt/mdt_reint.c b/lustre/mdt/mdt_reint.c
index 455ea85..cfd693d 100644 (file)
--- a/lustre/mdt/mdt_reint.c
+++ b/lustre/mdt/mdt_reint.c
@@ -879,6 +879,11 @@ static int mdt_reint_link(struct mdt_thread_info *info,
                 GOTO(out_unlock_child, rc);
         /* save version of file name for replay, it must be ENOENT here */
         if (!req_is_replay(mdt_info_req(info))) {
+               if (rc != -ENOENT) {
+                       CDEBUG(D_INFO, "link target %.*s existed!\n",
+                              rr->rr_namelen, (char *)rr->rr_name);
+                       GOTO(out_unlock_child, rc = -EEXIST);
+               }
                 info->mti_ver[2] = ENOENT_VERSION;
                 mdt_version_save(mdt_info_req(info), info->mti_ver[2], 2);
         }

diff --git a/lustre/tests/mlink.c b/lustre/tests/mlink.c
index ed34591..859201b 100755 (executable)
--- a/lustre/tests/mlink.c
+++ b/lustre/tests/mlink.c
@@ -44,18 +44,18 @@
 
 int main(int argc, char ** argv)
 {
-        int rc;
+       int rc;
 
-        if (argc < 3) { 
-                printf("Usage: %s file link\n", argv[0]);
-                return 1;
-        }
+       if (argc < 3) {
+               fprintf(stderr, "usage: %s file link\n", argv[0]);
+               return 1;
+       }
 
-        rc = link(argv[1], argv[2]);
-        if (rc) { 
-                printf("link(%s, %s) error: %s\n", argv[1], argv[2],
-                      strerror(errno));
+       rc = link(argv[1], argv[2]);
+       if (rc) {
+               fprintf(stderr, "link(%s, %s) error: %s\n",
+                       argv[1], argv[2], strerror(errno));
                return errno;
-        }
+       }
        return 0;
-} 
+}

diff --git a/lustre/tests/sanity.sh b/lustre/tests/sanity.sh
index c5e583d..9537246 100644 (file)
--- a/lustre/tests/sanity.sh
+++ b/lustre/tests/sanity.sh
@@ -1736,6 +1736,38 @@ test_31m() {
 }
 run_test 31m "link to file: the same, non-existing, dir==============="
 
+link_one() {
+       local TEMPNAME=$(mktemp $1_XXXXXX)
+       mlink $TEMPNAME $1 2> /dev/null &&
+               echo "$BASHPID: link $TEMPNAME to $1 succeeded"
+       munlink $TEMPNAME
+}
+
+test_31o() { # LU-2901
+       local server_version=$(lustre_version_code $SINGLEMDS)
+
+       if [[ $server_version -lt $(version_code 2.1.6) ]] ||
+          [[ $server_version -ge $(version_code 2.2.0) &&
+             $server_version -lt $(version_code 2.4.1) ]]; then
+               skip "Need MDS version at least 2.1.6 or 2.4.1"
+               return 0
+       fi
+
+       mkdir -p $DIR/$tdir
+       for LOOP in $(seq 100); do
+               rm -f $DIR/$tdir/$tfile*
+               for THREAD in $(seq 8); do
+                       link_one $DIR/$tdir/$tfile.$LOOP &
+               done
+               wait
+               local LINKS=$(ls -1 $DIR/$tdir | grep -c $tfile.$LOOP)
+               [ $LINKS -gt 1 ] && ls $DIR/$tdir &&
+                       error "$LINKS duplicate links to $tfile.$LOOP" &&
+                       break || true
+       done
+}
+run_test 31o "duplicate hard links with same filename"
+
 test_32a() {
        echo "== more mountpoints and symlinks ================="
        [ -e $DIR/d32a ] && rm -fr $DIR/d32a