[7/7] btrfs: use feature attribute names to print better error messages

Commit Message

Jeff Mahoney Sept. 10, 2013, 4:24 a.m. UTC

Now that we have the feature name strings available in the kernel via
the sysfs attributes, we can use them for printing better failure
messages from the ioctl path.

Signed-off-by: Jeff Mahoney <[e-mail]>
---
 fs/btrfs/ioctl.c |   35 ++++++++++++++++++++++++++++++-----
 fs/btrfs/sysfs.c |   25 +++++++++++++++++++++++++
 fs/btrfs/sysfs.h |    3 +++
 3 files changed, 58 insertions(+), 5 deletions(-)



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Patch

--- a/fs/btrfs/ioctl.c	2013-09-09 23:23:34.794883859 -0400
+++ b/fs/btrfs/ioctl.c	2013-09-09 23:24:03.019073609 -0400
@@ -56,6 +56,7 @@ 
 #include "rcu-string.h"
 #include "send.h"
 #include "dev-replace.h"
+#include "sysfs.h"
 
 /* Mask out flags that are inappropriate for the given type of inode. */
 static inline __u32 btrfs_mask_flags(umode_t mode, __u32 flags)
@@ -4143,17 +4144,27 @@  static int btrfs_ioctl_get_features(stru
 	return 0;
 }
 
-static int check_feature_bits(struct btrfs_root *root, const char *type,
+static int check_feature_bits(struct btrfs_root *root,
+			      enum btrfs_feature_set set,
 			      u64 change_mask, u64 flags, u64 supported_flags,
 			      u64 safe_set, u64 safe_clear)
 {
+	const char *type = btrfs_feature_set_names[set];
+	char *names;
 	u64 disallowed, unsupported;
 	u64 set_mask = flags & change_mask;
 	u64 clear_mask = ~flags & change_mask;
 
 	unsupported = set_mask & ~supported_flags;
 	if (unsupported) {
-		btrfs_warn(root->fs_info,
+		names = btrfs_printable_features(set, unsupported);
+		if (names) {
+			btrfs_warn(root->fs_info,
+			   "this kernel does not support the %s feature bit%s",
+			   names, strchr(names, ',') ? "s" : "");
+			kfree(names);
+		} else
+			btrfs_warn(root->fs_info,
 			   "this kernel does not support %s bits 0x%llx",
 			   type, unsupported);
 		return -EOPNOTSUPP;
@@ -4161,7 +4172,14 @@  static int check_feature_bits(struct btr
 
 	disallowed = set_mask & ~safe_set;
 	if (disallowed) {
-		btrfs_warn(root->fs_info,
+		names = btrfs_printable_features(set, disallowed);
+		if (names) {
+			btrfs_warn(root->fs_info,
+			   "can't set the %s feature bit%s while mounted",
+			   names, strchr(names, ',') ? "s" : "");
+			kfree(names);
+		} else
+			btrfs_warn(root->fs_info,
 			   "can't set %s bits 0x%llx while mounted",
 			   type, disallowed);
 		return -EPERM;
@@ -4169,7 +4187,14 @@  static int check_feature_bits(struct btr
 
 	disallowed = clear_mask & ~safe_clear;
 	if (disallowed) {
-		btrfs_warn(root->fs_info,
+		names = btrfs_printable_features(set, disallowed);
+		if (names) {
+			btrfs_warn(root->fs_info,
+			   "can't clear the %s feature bit%s while mounted",
+			   names, strchr(names, ',') ? "s" : "");
+			kfree(names);
+		} else
+			btrfs_warn(root->fs_info,
 			   "can't clear %s bits 0x%llx while mounted",
 			   type, disallowed);
 		return -EPERM;
@@ -4179,7 +4204,7 @@  static int check_feature_bits(struct btr
 }
 
 #define check_feature(root, change_mask, flags, mask_base)	\
-check_feature_bits(root, # mask_base, change_mask, flags,	\
+check_feature_bits(root, FEAT_##mask_base, change_mask, flags,	\
 		   BTRFS_FEATURE_ ## mask_base ## _SUPP,	\
 		   BTRFS_FEATURE_ ## mask_base ## _SAFE_SET,	\
 		   BTRFS_FEATURE_ ## mask_base ## _SAFE_CLEAR)
--- a/fs/btrfs/sysfs.c	2013-09-09 23:24:02.991073420 -0400
+++ b/fs/btrfs/sysfs.c	2013-09-09 23:24:03.019073609 -0400
@@ -65,6 +65,31 @@  const char *btrfs_feature_set_names[FEAT
 static char btrfs_feature_names[FEAT_MAX][64][13];
 static struct btrfs_feature_attr btrfs_feature_attrs[FEAT_MAX][64];
 
+char *btrfs_printable_features(enum btrfs_feature_set set, u64 flags)
+{
+	size_t bufsize = 4096; /* safe max, 64 names * 64 bytes */
+	int len = 0;
+	int i;
+	char *str;
+
+	str = kmalloc(bufsize, GFP_KERNEL);
+	if (!str)
+		return str;
+
+	for (i = 0; i < ARRAY_SIZE(btrfs_feature_attrs[set]); i++) {
+		if (!(flags & (1ULL << i)))
+			continue;
+
+		flags &= ~(1ULL << i);
+
+		len += snprintf(str + len, bufsize - len,
+				"%s%s", len ? "," : "",
+				btrfs_feature_attrs[set][i].attr.name);
+	}
+
+	return str;
+}
+
 static void init_feature_set_attrs(enum btrfs_feature_set set)
 {
 	int i;
--- a/fs/btrfs/sysfs.h	2013-09-09 23:23:34.794883859 -0400
+++ b/fs/btrfs/sysfs.h	2013-09-09 23:24:03.019073609 -0400
@@ -53,4 +53,7 @@  static struct btrfs_feature_attr btrfs_a
 #define to_btrfs_feature_attr(a) \
 			container_of(a, struct btrfs_feature_attr, attr)
 
+char *btrfs_printable_features(enum btrfs_feature_set set, u64 flags);
+extern const char *btrfs_feature_set_names[FEAT_MAX];
+
 #endif /* _BTRFS_SYSFS_H_ */