features/quota: make writes short when the entire write cannot fit into available space.

This patch aims to prevent creation of infinite zero byte sized files
due to amount of storage available before exceeding quota limit
being less than write sizes. Imagine x bytes of storage is available
before we exceed quota limit and quota enforcer is receiving writes of
size y and (y > x). In this scenario, if we run a shell script like:

   # for i in $(seq 1 10); do dd if=/dev/zero of=$i bs=y count=1; done

Then, we would end up with 10 zero byte sized files, because we allow
only complete writes and all writes will fail because of lack of space.
However, creates succeed since a create itself will consume zero
bytes. In this pattern of creates and writes, size of volume would
never grow and x bytes of space will always be available and we can
end up with an infinite number of zero byte sized files.

Change-Id: Ice148d6a2207883e41759f7b0be73abaa3198b41
BUG: 1012216
Signed-off-by: Raghavendra G <rgowdapp@redhat.com>
Reviewed-on: http://review.gluster.org/6035
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>

2 files changed, 57 insertions, 10 deletions

diff --git a/xlators/features/quota/src/quota.c b/xlators/features/quota/src/quota.c
index a50fb1184..3c6c31def 100644
--- a/xlators/features/quota/src/quota.c
+++ b/xlators/features/quota/src/quota.c
@@ -191,8 +191,13 @@ quota_local_new ()
 {
         quota_local_t *local = NULL;
         local = mem_get0 (THIS->local_pool);
-        if (local)
-                LOCK_INIT (&local->lock);
+        if (local == NULL)
+                goto out;
+
+        LOCK_INIT (&local->lock);
+        local->space_available = -1;
+
+out:
         return local;
 }
 
@@ -342,7 +347,7 @@ quota_validate_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
         }
         UNLOCK (&ctx->lock);
 
-        quota_check_limit (frame, local->validate_loc.inode, this, NULL, NULL) ;
+        quota_check_limit (frame, local->validate_loc.inode, this, NULL, NULL);
         return 0;
 
 unwind:
@@ -653,6 +658,7 @@ quota_check_limit (call_frame_t *frame, inode_t *inode, xlator_t *this,
         char               need_validate       = 0;
         gf_boolean_t       hard_limit_exceeded = 0;
         int64_t            delta               = 0, wouldbe_size = 0;
+        int64_t            space_available     = 0;
         uint64_t           value               = 0;
         char               just_validated      = 0;
         uuid_t             trav_uuid           = {0,};
@@ -742,10 +748,22 @@ quota_check_limit (call_frame_t *frame, inode_t *inode, xlator_t *this,
                         }
 
                         if (hard_limit_exceeded) {
-                                op_errno = EDQUOT;
-                                goto err;
-                        }
+                                local->op_ret = -1;
+                                local->op_errno = EDQUOT;
+
+                                space_available = ctx->hard_lim - ctx->size;
+
+                                if (space_available < 0)
+                                        space_available = 0;
 
+                                if ((local->space_available < 0)
+                                    || (local->space_available
+                                        > space_available)){
+                                        local->space_available
+                                                = space_available;
+
+                                }
+                        }
                 }
 
                 if (__is_root_gfid (_inode->gfid)) {
@@ -1139,9 +1157,11 @@ quota_writev_helper (call_frame_t *frame, xlator_t *this, fd_t *fd,
                      struct iovec *vector, int32_t count, off_t off,
                      uint32_t flags, struct iobref *iobref, dict_t *xdata)
 {
-        quota_local_t *local    = NULL;
-        int32_t        op_errno = EINVAL;
-        quota_priv_t  *priv     = NULL;
+        quota_local_t *local      = NULL;
+        int32_t        op_errno   = EINVAL;
+        quota_priv_t  *priv       = NULL;
+        struct iovec  *new_vector = NULL;
+        int32_t        new_count  = 0;
 
         priv = this->private;
 
@@ -1153,13 +1173,39 @@ quota_writev_helper (call_frame_t *frame, xlator_t *this, fd_t *fd,
 
         if (local->op_ret == -1) {
                 op_errno = local->op_errno;
-                goto unwind;
+
+                if ((op_errno == EDQUOT) && (local->space_available > 0)) {
+                        new_count = iov_subset (vector, count, 0,
+                                                local->space_available, NULL);
+
+                        new_vector = GF_CALLOC (new_count,
+                                                sizeof (struct iovec),
+                                                gf_common_mt_iovec);
+                        if (new_vector == NULL) {
+                                local->op_ret = -1;
+                                local->op_errno = ENOMEM;
+                                goto unwind;
+                        }
+
+                        new_count = iov_subset (vector, count, 0,
+                                                local->space_available,
+                                                new_vector);
+
+                        vector = new_vector;
+                        count = new_count;
+                } else {
+                        goto unwind;
+                }
         }
 
         STACK_WIND (frame,
                     priv->is_quota_on? quota_writev_cbk: default_writev_cbk,
                     FIRST_CHILD(this), FIRST_CHILD(this)->fops->writev, fd,
                     vector, count, off, flags, iobref, xdata);
+
+        if (new_vector != NULL)
+                GF_FREE (new_vector);
+
         return 0;
 
 unwind:
diff --git a/xlators/features/quota/src/quota.h b/xlators/features/quota/src/quota.h
index de522e691..96c19e77e 100644
--- a/xlators/features/quota/src/quota.h
+++ b/xlators/features/quota/src/quota.h
@@ -176,6 +176,7 @@ struct quota_local {
         call_stub_t        *stub;
         struct iobref      *iobref;
         quota_limit_t       limit;
+        int64_t             space_available;
 };
 typedef struct quota_local  quota_local_t;