features/snapview-server: check if the reference to the snapshot world is correct before doing any fop

The following operations might lead to problems:
* Create a file on the glusterfs mount point
* Create a snapshot (say "snap1")
* Access the contents of the snapshot
* Delete the file from the mount point
* Delete the snapshot "snap1"
* Create a new snapshot "snap1"

Now accessing the new snapshot "snap1" gives problems. Because the inode and
dentry created for snap1 would not be deleted upon the deletion of the snapshot
(as deletion of snapshot is a gluster cli operation, not a fop). So next time
upon creation of a new snap with same name, the previous inode and dentry itself
will be used. But the inode context contains old information about the glfs_t
instance and the handle in the gfapi world. Directly accessing them without
proper check leads to ENOTCONN errors. Thus the glfs_t instance should be
checked before accessing. If its wrong, then right instance should be obtained
by doing the lookup.

Change-Id: I975245b8f6b7fea0a90eb5e36e8149d12457ac10
BUG: 1158791
Reviewed-on: http://review.gluster.org/9007
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Vijay Bellur <vbellur@redhat.com>

3 files changed, 75 insertions, 8 deletions

diff --git a/tests/basic/uss.t b/tests/basic/uss.t
index 0cd42ac177c..76c1deaf9ae 100644
--- a/tests/basic/uss.t
+++ b/tests/basic/uss.t
@@ -271,4 +271,40 @@ function count_snaps
 
 EXPECT_WITHIN 30 "5" count_snaps $M0;
 
+# deletion of a snapshot and creation of a new snapshot with same name
+# should not create problems. The data that was supposed to be present
+# in the deleted snapshot need not be present in the new snapshot just
+# because the name is same. Ex:
+# 1) Create a file "aaa"
+# 2) Create a snapshot snap6
+# 3) stat the file "aaa" in snap6 and it should succeed
+# 4) delete the file "aaa"
+# 5) Delete the snapshot snap6
+# 6) Create a snapshot snap6
+# 7) stat the file "aaa" in snap6 and it should fail now
+
+echo "aaa" > $M0/aaa;
+
+TEST $CLI snapshot create snap6 $V0
+
+TEST ls $M0/.history;
+
+EXPECT_WITHIN 30 "6" count_snaps $M0;
+
+TEST stat $M0/.history/snap6/aaa
+
+TEST rm -f $M0/aaa;
+
+TEST $CLI snapshot delete snap6;
+
+TEST $CLI snapshot create snap6 $V0
+
+TEST ls $M0/.history;
+
+EXPECT_WITHIN 30 "6" count_snaps $M0;
+
+TEST ls $M0/.history/snap6/;
+
+TEST ! stat $M0/.history/snap6/aaa;
+
 cleanup;
diff --git a/xlators/features/snapview-server/src/snapview-server.c b/xlators/features/snapview-server/src/snapview-server.c
index a9c95850f3e..4bb8e3be8f3 100644
--- a/xlators/features/snapview-server/src/snapview-server.c
+++ b/xlators/features/snapview-server/src/snapview-server.c
@@ -254,7 +254,7 @@ svs_lookup_snapshot (xlator_t *this, loc_t *loc, struct iatt *buf,
         iatt_from_stat (buf, &statbuf);
         uuid_copy (buf->ia_gfid, gfid);
         svs_fill_ino_from_gfid (buf);
-        inode_ctx->type = SNAP_VIEW_VIRTUAL_INODE;
+        inode_ctx->type = SNAP_VIEW_SNAPSHOT_INODE;
         inode_ctx->fs = fs;
         inode_ctx->object = object;
         memcpy (&inode_ctx->buf, buf, sizeof (*buf));
@@ -574,7 +574,8 @@ svs_opendir (call_frame_t *frame, xlator_t *this, loc_t *loc, fd_t *fd,
                 op_ret = 0;
                 op_errno = 0;
                 goto out;
-        } else if (inode_ctx->type == SNAP_VIEW_VIRTUAL_INODE) {
+        }
+        else {
 
                 SVS_GET_INODE_CTX_INFO(inode_ctx, fs, object, this, loc, op_ret,
                                        op_errno, out);
@@ -702,7 +703,8 @@ svs_getxattr (call_frame_t *frame, xlator_t *this, loc_t *loc, const char *name,
                 op_ret = -1;
                 op_errno = EINVAL;
                 goto out;
-        } else if (inode_ctx->type == SNAP_VIEW_VIRTUAL_INODE) {
+        }
+        else {
 
                 SVS_GET_INODE_CTX_INFO(inode_ctx, fs, object, this, loc, op_ret,
                                        op_errno, out);
@@ -832,8 +834,7 @@ svs_fgetxattr (call_frame_t *frame, xlator_t *this, fd_t *fd, const char *name,
                 op_errno = EINVAL;
                 goto out;
         }
-
-        if (inode_ctx->type == SNAP_VIEW_VIRTUAL_INODE) {
+        else {
                 dict = dict_new ();
                 if (!dict) {
                         gf_log (this->name, GF_LOG_ERROR, "failed to "
@@ -1270,16 +1271,17 @@ svs_readdirp_fill (xlator_t *this, inode_t *parent, svs_inode_t *parent_ctx,
                         goto out;
                 }
 
-                inode_ctx->type = SNAP_VIEW_VIRTUAL_INODE;
 
                 if (parent_ctx->type == SNAP_VIEW_ENTRY_POINT_INODE) {
                         buf.ia_type = IA_IFDIR;
                         inode_ctx->buf = buf;
                         entry->d_stat = buf;
+                        inode_ctx->type = SNAP_VIEW_SNAPSHOT_INODE;
                 } else {
                         uuid_copy (entry->d_stat.ia_gfid, buf.ia_gfid);
                         entry->d_stat.ia_ino = buf.ia_ino;
                         inode_ctx->buf = entry->d_stat;
+                        inode_ctx->type = SNAP_VIEW_VIRTUAL_INODE;
                 }
         }
 
@@ -1592,7 +1594,8 @@ svs_stat (call_frame_t *frame, xlator_t *this, loc_t *loc, dict_t *xdata)
         if (inode_ctx->type == SNAP_VIEW_ENTRY_POINT_INODE) {
                 svs_iatt_fill (loc->inode->gfid, &buf);
                 op_ret = 0;
-        } else if (inode_ctx->type == SNAP_VIEW_VIRTUAL_INODE) {
+        }
+        else {
 
                 SVS_GET_INODE_CTX_INFO(inode_ctx, fs, object, this, loc, op_ret,
                                        op_errno, out);
@@ -1655,7 +1658,8 @@ svs_fstat (call_frame_t *frame, xlator_t *this, fd_t *fd, dict_t *xdata)
         if (inode_ctx->type == SNAP_VIEW_ENTRY_POINT_INODE) {
                 svs_iatt_fill (fd->inode->gfid, &buf);
                 op_ret = 0;
-        } else if (inode_ctx->type == SNAP_VIEW_VIRTUAL_INODE) {
+        }
+        else {
                 sfd = svs_fd_ctx_get_or_new (this, fd);
                 if (!sfd) {
                         gf_log (this->name, GF_LOG_ERROR, "failed to get the "
diff --git a/xlators/features/snapview-server/src/snapview-server.h b/xlators/features/snapview-server/src/snapview-server.h
index 4b42aefcd98..47effb19758 100644
--- a/xlators/features/snapview-server/src/snapview-server.h
+++ b/xlators/features/snapview-server/src/snapview-server.h
@@ -53,11 +53,37 @@
                 STACK_DESTROY (((call_frame_t *)_frame)->root);     \
         } while (0)
 
+#define SVS_CHECK_VALID_SNAPSHOT_HANDLE(fs, this)                       \
+        do {                                                            \
+                svs_private_t *_private = NULL;                         \
+                _private = this->private;                               \
+                int  i = 0;                                             \
+                gf_boolean_t found = _gf_false;                         \
+                LOCK (&_private->snaplist_lock);                        \
+                {                                                       \
+                        for (i = 0; i < _private->num_snaps; i++) {     \
+                                if (_private->dirents->fs && fs &&      \
+                                    _private->dirents->fs == fs) {      \
+                                        found = _gf_true;               \
+                                        break;                          \
+                                }                                       \
+                        }                                               \
+                }                                                       \
+                UNLOCK (&_private->snaplist_lock);                      \
+                                                                        \
+                if (!found)                                             \
+                        fs = NULL;                                      \
+        } while (0)
+
 #define SVS_GET_INODE_CTX_INFO(inode_ctx, fs, object, this, loc, ret,   \
                                op_errno, label)                         \
         do {                                                            \
                 fs = inode_ctx->fs;                                     \
                 object = inode_ctx->object;                             \
+                SVS_CHECK_VALID_SNAPSHOT_HANDLE (fs, this);             \
+                if (!fs)                                                \
+                        object = NULL;                                  \
+                                                                        \
                 if (!fs || !object) {                                   \
                         int32_t tmp = -1;                               \
                         char    tmp_uuid[64];                           \
@@ -94,6 +120,7 @@ mgmt_get_snapinfo_cbk (struct rpc_req *req, struct iovec *iov,
 
 typedef enum {
         SNAP_VIEW_ENTRY_POINT_INODE = 0,
+        SNAP_VIEW_SNAPSHOT_INODE,
         SNAP_VIEW_VIRTUAL_INODE
 } inode_type_t;