[PATCH] btrfs filesystem show: skip duplicate fsids

[Chris Mason <chris.mason@fusionio.com>]

If a given filesystem is mounted more than once, btrfs fi show will
print dups.  This adds a quick and dirty hash table of fsids it
has already printed and makes sure we don't print any fsid more than
once.

Anand has other patches that solve this by pulling information in from
new kernel interfaces.  For now, we'll do the duplicate searching.

Signed-off-by: Chris Mason <chris.mason@fusionio.com>
---
 cmds-filesystem.c | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)

diff --git a/cmds-filesystem.c b/cmds-filesystem.c
index aa361d6..1c1926b 100644
--- a/cmds-filesystem.c
+++ b/cmds-filesystem.c
@@ -38,6 +38,74 @@
 #include "commands.h"
 #include "list_sort.h"
 
+
+/*
+ * for btrfs fi show, we maintain a hash of fsids we've already printed.
+ * This way we don't print dups if a given FS is mounted more than once.
+ */
+#define SEEN_FSID_HASH_SIZE 256
+
+struct seen_fsid {
+	u8 fsid[BTRFS_FSID_SIZE];
+	struct seen_fsid *next;
+};
+
+static struct seen_fsid *seen_fsid_hash[SEEN_FSID_HASH_SIZE] = {NULL,};
+
+static int add_seen_fsid(u8 *fsid)
+{
+	u8 hash = fsid[0];
+	int slot = hash % SEEN_FSID_HASH_SIZE;
+	struct seen_fsid *seen = seen_fsid_hash[slot];
+	struct seen_fsid *alloc;
+
+	if (!seen)
+		goto insert;
+
+	while (1) {
+		if (memcmp(seen->fsid, fsid, BTRFS_FSID_SIZE) == 0)
+			return -EEXIST;
+
+		if (!seen->next)
+			break;
+
+		seen = seen->next;
+	}
+
+insert:
+
+	alloc = malloc(sizeof(*alloc));
+	if (!alloc)
+		return -ENOMEM;
+
+	alloc->next = NULL;
+	memcpy(alloc->fsid, fsid, BTRFS_FSID_SIZE);
+
+	if (seen)
+		seen->next = alloc;
+	else
+		seen_fsid_hash[slot] = alloc;
+
+	return 0;
+}
+
+static void free_seen_fsid(void)
+{
+	int slot;
+	struct seen_fsid *seen;
+	struct seen_fsid *next;
+
+	for (slot = 0; slot < SEEN_FSID_HASH_SIZE; slot++) {
+		seen = seen_fsid_hash[slot];
+		while (seen) {
+			next = seen->next;
+			free(seen);
+			seen = next;
+		}
+		seen_fsid_hash[slot] = NULL;
+	}
+}
+
 static const char * const filesystem_cmd_group_usage[] = {
 	"btrfs filesystem [<group>] <command> [<args>]",
 	NULL
@@ -224,6 +292,9 @@ static void print_one_uuid(struct btrfs_fs_devices *fs_devices)
 	u64 devs_found = 0;
 	u64 total;
 
+	if (add_seen_fsid(fs_devices->fsid))
+		return;
+
 	uuid_unparse(fs_devices->fsid, uuidbuf);
 	device = list_entry(fs_devices->devices.next, struct btrfs_device,
 			    dev_list);
@@ -274,6 +345,13 @@ static int print_one_fs(struct btrfs_ioctl_fs_info_args *fs_info,
 	int i;
 	char uuidbuf[37];
 	struct btrfs_ioctl_dev_info_args *tmp_dev_info;
+	int ret;
+
+	ret = add_seen_fsid(fs_info->fsid);
+	if (ret == -EEXIST)
+		return 0;
+	else if (ret)
+		return ret;
 
 	uuid_unparse(fs_info->fsid, uuidbuf);
 	printf("Label: %s  uuid: %s\n",
@@ -478,6 +556,7 @@ devs_only:
 
 out:
 	printf("%s\n", BTRFS_BUILD_VERSION);
+	free_seen_fsid();
 	return 0;
 }
 
-- 
1.8.2