afr: write zeros to sink for non-sparse files

Problem: If a file is created with zeroes ('dd', 'fallocate' etc.) when
a brick is down, the self-heal does not write the zeroes to the sink
after it comes up. Consequenty, there is a mismatch in disk-usage
amongst the bricks of the replica.

Fix: If we definitely know that the file is not sparse, then write the
zeroes to the sink even if the checksums match.

Change-Id: Ic739b3da5dbf47d99801c0e1743bb13aeb3af864
BUG: 1272460
Signed-off-by: Ravishankar N <ravishankar@redhat.com>
Reviewed-on: http://review.gluster.org/12371
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>

3 files changed, 78 insertions, 24 deletions

diff --git a/xlators/cluster/afr/src/afr-self-heal-data.c b/xlators/cluster/afr/src/afr-self-heal-data.c
index 36d658fa454..4529462c3a9 100644
--- a/xlators/cluster/afr/src/afr-self-heal-data.c
+++ b/xlators/cluster/afr/src/afr-self-heal-data.c
@@ -28,13 +28,18 @@ __checksum_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
 		dict_t *xdata)
 {
 	afr_local_t *local = NULL;
+        struct afr_reply *replies = NULL;
 	int i = (long) cookie;
 
 	local = frame->local;
-
-	local->replies[i].valid = 1;
-	local->replies[i].op_ret = op_ret;
-	local->replies[i].op_errno = op_errno;
+        replies = local->replies;
+
+	replies[i].valid = 1;
+	replies[i].op_ret = op_ret;
+	replies[i].op_errno = op_errno;
+        if (xdata)
+                replies[i].buf_has_zeroes = dict_get_str_boolean (xdata,
+                                                   "buf-has-zeroes", _gf_false);
 	if (strong)
 		memcpy (local->replies[i].checksum, strong, MD5_DIGEST_LENGTH);
 
@@ -70,19 +75,23 @@ attr_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
 
 
 static gf_boolean_t
-__afr_selfheal_data_checksums_match (call_frame_t *frame, xlator_t *this,
-				     fd_t *fd, int source,
-				     unsigned char *healed_sinks,
-				     off_t offset, size_t size)
+__afr_can_skip_data_block_heal (call_frame_t *frame, xlator_t *this, fd_t *fd,
+                                int source, unsigned char *healed_sinks,
+				off_t offset, size_t size,
+                                struct iatt *poststat)
 {
 	afr_private_t *priv = NULL;
 	afr_local_t *local = NULL;
 	unsigned char *wind_subvols = NULL;
+        gf_boolean_t checksum_match = _gf_true;
+        dict_t *xdata = NULL;
 	int i = 0;
 
 	priv = this->private;
 	local = frame->local;
-
+        xdata = dict_new();
+        if (xdata)
+                i = dict_set_int32 (xdata, "check-zero-filled", 1);
 	wind_subvols = alloca0 (priv->child_count);
 	for (i = 0; i < priv->child_count; i++) {
 		if (i == source || healed_sinks[i])
@@ -90,7 +99,9 @@ __afr_selfheal_data_checksums_match (call_frame_t *frame, xlator_t *this,
 	}
 
 	AFR_ONLIST (wind_subvols, frame, __checksum_cbk, rchecksum, fd,
-		    offset, size, NULL);
+		    offset, size, xdata);
+        if (xdata)
+                dict_unref (xdata);
 
 	if (!local->replies[source].valid || local->replies[source].op_ret != 0)
 		return _gf_false;
@@ -101,12 +112,26 @@ __afr_selfheal_data_checksums_match (call_frame_t *frame, xlator_t *this,
                 if (local->replies[i].valid) {
                         if (memcmp (local->replies[source].checksum,
                                     local->replies[i].checksum,
-                                    MD5_DIGEST_LENGTH))
-                                return _gf_false;
+                                    MD5_DIGEST_LENGTH)) {
+                                checksum_match = _gf_false;
+                                break;
+                        }
                 }
 	}
 
-	return _gf_true;
+        if (checksum_match) {
+                if (HAS_HOLES (poststat))
+                        return _gf_true;
+
+                /* For non-sparse files, we might be better off writing the
+                 * zeroes to sinks to avoid mismatch of disk-usage in bricks. */
+                if (local->replies[source].buf_has_zeroes)
+                        return _gf_false;
+                else
+                        return _gf_true;
+        }
+
+        return _gf_false;
 }
 
 
@@ -220,7 +245,6 @@ __afr_selfheal_data_read_write (call_frame_t *frame, xlator_t *this, fd_t *fd,
 	return ret;
 }
 
-
 static int
 afr_selfheal_data_block (call_frame_t *frame, xlator_t *this, fd_t *fd,
 			 int source, unsigned char *healed_sinks, off_t offset,
@@ -244,8 +268,9 @@ afr_selfheal_data_block (call_frame_t *frame, xlator_t *this, fd_t *fd,
 		}
 
 		if (type == AFR_SELFHEAL_DATA_DIFF &&
-		    __afr_selfheal_data_checksums_match (frame, this, fd, source,
-							 healed_sinks, offset, size)) {
+		    __afr_can_skip_data_block_heal (frame, this, fd, source,
+					            healed_sinks, offset, size,
+                                                   &replies[source].poststat)) {
 			ret = 0;
 			goto unlock;
 		}
diff --git a/xlators/cluster/afr/src/afr.h b/xlators/cluster/afr/src/afr.h
index bd4ff655546..28147e00579 100644
--- a/xlators/cluster/afr/src/afr.h
+++ b/xlators/cluster/afr/src/afr.h
@@ -265,7 +265,9 @@ struct afr_reply {
 	struct iatt preparent;
 	struct iatt preparent2;
 	struct iatt postparent2;
+        /* For rchecksum */
 	uint8_t checksum[MD5_DIGEST_LENGTH];
+        gf_boolean_t buf_has_zeroes;
 };
 
 typedef enum {
diff --git a/xlators/storage/posix/src/posix.c b/xlators/storage/posix/src/posix.c
index bc4e4904b74..b544e3739c6 100644
--- a/xlators/storage/posix/src/posix.c
+++ b/xlators/storage/posix/src/posix.c
@@ -5895,9 +5895,13 @@ posix_rchecksum (call_frame_t *frame, xlator_t *this,
         int                     op_ret          = -1;
         int                     op_errno        = 0;
         int                     ret             = 0;
+        ssize_t                 bytes_read      = 0;
         int32_t                 weak_checksum   = 0;
+        int32_t                 zerofillcheck   = 0;
         unsigned char           strong_checksum[MD5_DIGEST_LENGTH] = {0};
         struct posix_private    *priv           = NULL;
+        dict_t                  *rsp_xdata      = NULL;
+        gf_boolean_t            buf_has_zeroes  = _gf_false;
 
         VALIDATE_OR_GOTO (frame, out);
         VALIDATE_OR_GOTO (this, out);
@@ -5912,6 +5916,12 @@ posix_rchecksum (call_frame_t *frame, xlator_t *this,
                 goto out;
         }
 
+        rsp_xdata = dict_new();
+        if (!rsp_xdata) {
+                op_errno = ENOMEM;
+                goto out;
+        }
+
         ret = posix_fd_ctx_get (fd, this, &pfd);
         if (ret < 0) {
                 gf_msg (this->name, GF_LOG_WARNING, -ret, P_MSG_PFD_NULL,
@@ -5927,12 +5937,12 @@ posix_rchecksum (call_frame_t *frame, xlator_t *this,
                 if (priv->aio_capable && priv->aio_init_done)
                         __posix_fd_set_odirect (fd, pfd, 0, offset, len);
 
-                ret = pread (_fd, buf, len, offset);
-                if (ret < 0) {
+                bytes_read = pread (_fd, buf, len, offset);
+                if (bytes_read < 0) {
                         gf_msg (this->name, GF_LOG_WARNING, errno,
                                 P_MSG_PREAD_FAILED,
-                                "pread of %d bytes returned %d ",
-                                len, ret);
+                                "pread of %d bytes returned %ld ",
+                                len, bytes_read);
 
                         op_errno = errno;
                 }
@@ -5940,17 +5950,34 @@ posix_rchecksum (call_frame_t *frame, xlator_t *this,
         }
         UNLOCK (&fd->lock);
 
-        if (ret < 0)
+        if (bytes_read < 0)
                 goto out;
 
+        if (xdata && dict_get_int32 (xdata, "check-zero-filled",
+                                     &zerofillcheck) == 0) {
+                buf_has_zeroes = (mem_0filled (buf, bytes_read)) ? _gf_false :
+                                 _gf_true;
+                ret = dict_set_uint32 (rsp_xdata, "buf-has-zeroes",
+                                       buf_has_zeroes);
+                if (ret) {
+                        gf_msg (this->name, GF_LOG_WARNING, -ret,
+                                P_MSG_DICT_SET_FAILED, "%s: Failed to set "
+                                "dictionary value for key: %s",
+                                uuid_utoa (fd->inode->gfid), "buf-has-zeroes");
+                        op_errno = -ret;
+                        goto out;
+                }
+        }
         weak_checksum = gf_rsync_weak_checksum ((unsigned char *) buf, (size_t) ret);
-        gf_rsync_strong_checksum ((unsigned char *) buf, (size_t) ret, (unsigned char *) strong_checksum);
+        gf_rsync_strong_checksum ((unsigned char *) buf, (size_t) bytes_read,
+                                  (unsigned char *) strong_checksum);
 
         op_ret = 0;
 out:
         STACK_UNWIND_STRICT (rchecksum, frame, op_ret, op_errno,
-                             weak_checksum, strong_checksum, NULL);
-
+                             weak_checksum, strong_checksum, rsp_xdata);
+        if (rsp_xdata)
+                dict_unref (rsp_xdata);
         GF_FREE (alloc_buf);
 
         return 0;