[PATCH v6] ubifs: respect MS_SILENT mount flag

[Daniel Golle <daniel@makrotopia.org>]

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When attempting to mount a non-ubifs formatted volume, lots of error
messages (including a stack dump) are thrown to the kernel log even if
the MS_SILENT mount flag is set.
Fix this by introducing adding an additional state-variable in
struct ubifs_info and suppress error messages in ubifs_read_node if
MS_SILENT is set.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
v6: added comments
v5: added missing semi-colon and fixed a style issue
v4: enclose conditional error printing macro by do { } while (0)
v3: use state variable in ubifs_info instead of a function parameter

 fs/ubifs/io.c    | 16 +++++++++-------
 fs/ubifs/super.c |  5 +++++
 fs/ubifs/ubifs.h | 12 ++++++++++++
 3 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/fs/ubifs/io.c b/fs/ubifs/io.c
index e18b988..3205929 100644
--- a/fs/ubifs/io.c
+++ b/fs/ubifs/io.c
@@ -988,30 +988,32 @@ int ubifs_read_node(const struct ubifs_info *c, void *buf, int type, int len,
 		return err;
 
 	if (type != ch->node_type) {
-		ubifs_err("bad node type (%d but expected %d)",
+		ubifs_errc(c, "bad node type (%d but expected %d)",
 			  ch->node_type, type);
 		goto out;
 	}
 
 	err = ubifs_check_node(c, buf, lnum, offs, 0, 0);
 	if (err) {
-		ubifs_err("expected node type %d", type);
+		ubifs_errc(c, "expected node type %d", type);
 		return err;
 	}
 
 	l = le32_to_cpu(ch->len);
 	if (l != len) {
-		ubifs_err("bad node length %d, expected %d", l, len);
+		ubifs_errc(c, "bad node length %d, expected %d", l, len);
 		goto out;
 	}
 
 	return 0;
 
 out:
-	ubifs_err("bad node at LEB %d:%d, LEB mapping status %d", lnum, offs,
-		  ubi_is_mapped(c->ubi, lnum));
-	ubifs_dump_node(c, buf);
-	dump_stack();
+	ubifs_errc(c, "bad node at LEB %d:%d, LEB mapping status %d", lnum,
+		  offs, ubi_is_mapped(c->ubi, lnum));
+	if (!c->probing) {
+		ubifs_dump_node(c, buf);
+		dump_stack();
+	}
 	return -EINVAL;
 }
 
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index a81c7b5..3904c85 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -1149,6 +1149,9 @@ static int mount_ubifs(struct ubifs_info *c)
 	size_t sz;
 
 	c->ro_mount = !!(c->vfs_sb->s_flags & MS_RDONLY);
+	/* Suppress error messages while probing if MS_SILENT is set */
+	c->probing = !!(c->vfs_sb->s_flags & MS_SILENT);
+
 	err = init_constants_early(c);
 	if (err)
 		return err;
@@ -1214,6 +1217,8 @@ static int mount_ubifs(struct ubifs_info *c)
 	if (err)
 		goto out_free;
 
+	c->probing = 0;
+
 	/*
 	 * Make sure the compressor which is set as default in the superblock
 	 * or overridden by mount options is actually compiled in.
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index e8c8cfe..f87ab74 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -52,6 +52,16 @@
 	pr_warn("UBIFS warning (pid %d): %s: " fmt "\n",            \
 		current->pid, __func__, ##__VA_ARGS__)
 
+/*
+ * A variant of 'ubifs_err()' which takes the UBIFS file-sytem description
+ * object as an argument.
+ */
+#define ubifs_errc(c, fmt, ...)                                    \
+	do {                                                       \
+		if (!(c)->probing)                                 \
+			ubifs_err(fmt, ##__VA_ARGS__);             \
+	} while (0)
+
 /* UBIFS file system VFS magic number */
 #define UBIFS_SUPER_MAGIC 0x24051905
 
@@ -1209,6 +1219,7 @@ struct ubifs_debug_info;
  * @need_recovery: %1 if the file-system needs recovery
  * @replaying: %1 during journal replay
  * @mounting: %1 while mounting
+ * @probing: %1 while attempting to mount if MS_SILENT mount flag is set
  * @remounting_rw: %1 while re-mounting from R/O mode to R/W mode
  * @replay_list: temporary list used during journal replay
  * @replay_buds: list of buds to replay
@@ -1441,6 +1452,7 @@ struct ubifs_info {
 	unsigned int replaying:1;
 	unsigned int mounting:1;
 	unsigned int remounting_rw:1;
+	unsigned int probing:1;
 	struct list_head replay_list;
 	struct list_head replay_buds;
 	unsigned long long cs_sqnum;
-- 
1.9.3


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