btrfs: sanity mount option parsing and early mount code

Also adds lots of comments to describe what's going on here.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 1dcf4fb..49cbc62 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1616,7 +1616,6 @@ int btrfs_delete_xattrs(struct btrfs_trans_handle *trans,
                        struct btrfs_root *root, struct inode *inode);
 /* super.c */
 u64 btrfs_parse_size(char *str);
-int btrfs_parse_options(char *options, struct btrfs_root *root,
-                       char **subvol_name);
+int btrfs_parse_options(struct btrfs_root *root, char *options);
 int btrfs_sync_fs(struct super_block *sb, int wait);
 #endif

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 3805e7e..b9a5364 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1266,8 +1266,11 @@ struct btrfs_root *open_ctree(struct super_block *sb,
        if (!btrfs_super_root(disk_super))
                goto fail_sb_buffer;
 
-       btrfs_parse_options(options, tree_root, NULL);
+       err = btrfs_parse_options(tree_root, options);
+       if (err)
+               goto fail_sb_buffer;
 
+       err = -EINVAL;
        if (btrfs_super_num_devices(disk_super) > fs_devices->open_devices) {
                printk("Btrfs: wanted %llu devices, but found %llu\n",
                       (unsigned long long)btrfs_super_num_devices(disk_super),

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 39bb869..288300f 100644 (file)
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -108,15 +108,18 @@ u64 btrfs_parse_size(char *str)
        return res;
 }
 
-int btrfs_parse_options(char *options, struct btrfs_root *root,
-                       char **subvol_name)
+/*
+ * Regular mount options parser.  Everything that is needed only when
+ * reading in a new superblock is parsed here.
+ */
+int btrfs_parse_options(struct btrfs_root *root, char *options)
 {
-       char * p;
-       struct btrfs_fs_info *info = NULL;
+       struct btrfs_fs_info *info = root->fs_info;
        substring_t args[MAX_OPT_ARGS];
+       char *p, *num;
 
        if (!options)
-               return 1;
+               return 0;
 
        /*
         * strsep changes the string, duplicate it because parse_options
@@ -126,10 +129,8 @@ int btrfs_parse_options(char *options, struct btrfs_root *root,
        if (!options)
                return -ENOMEM;
 
-       if (root)
-               info = root->fs_info;
 
-       while ((p = strsep (&options, ",")) != NULL) {
+       while ((p = strsep(&options, ",")) != NULL) {
                int token;
                if (!*p)
                        continue;
@@ -137,83 +138,64 @@ int btrfs_parse_options(char *options, struct btrfs_root *root,
                token = match_token(p, tokens, args);
                switch (token) {
                case Opt_degraded:
-                       if (info) {
-                               printk("btrfs: allowing degraded mounts\n");
-                               btrfs_set_opt(info->mount_opt, DEGRADED);
-                       }
+                       printk(KERN_INFO "btrfs: allowing degraded mounts\n");
+                       btrfs_set_opt(info->mount_opt, DEGRADED);
                        break;
                case Opt_subvol:
-                       if (subvol_name) {
-                               *subvol_name = match_strdup(&args[0]);
-                       }
+                       /*
+                        * This one is parsed by btrfs_parse_early_options
+                        * and can be happily ignored here.
+                        */
                        break;
                case Opt_nodatasum:
-                       if (info) {
-                               printk("btrfs: setting nodatacsum\n");
-                               btrfs_set_opt(info->mount_opt, NODATASUM);
-                       }
+                       printk(KERN_INFO "btrfs: setting nodatacsum\n");
+                       btrfs_set_opt(info->mount_opt, NODATASUM);
                        break;
                case Opt_nodatacow:
-                       if (info) {
-                               printk("btrfs: setting nodatacow\n");
-                               btrfs_set_opt(info->mount_opt, NODATACOW);
-                               btrfs_set_opt(info->mount_opt, NODATASUM);
-                       }
+                       printk(KERN_INFO "btrfs: setting nodatacow\n");
+                       btrfs_set_opt(info->mount_opt, NODATACOW);
+                       btrfs_set_opt(info->mount_opt, NODATASUM);
                        break;
                case Opt_ssd:
-                       if (info) {
-                               printk("btrfs: use ssd allocation scheme\n");
-                               btrfs_set_opt(info->mount_opt, SSD);
-                       }
+                       printk(KERN_INFO "btrfs: use ssd allocation scheme\n");
+                       btrfs_set_opt(info->mount_opt, SSD);
                        break;
                case Opt_nobarrier:
-                       if (info) {
-                               printk("btrfs: turning off barriers\n");
-                               btrfs_set_opt(info->mount_opt, NOBARRIER);
-                       }
+                       printk(KERN_INFO "btrfs: turning off barriers\n");
+                       btrfs_set_opt(info->mount_opt, NOBARRIER);
                        break;
                case Opt_max_extent:
-                       if (info) {
-                               char *num = match_strdup(&args[0]);
-                               if (num) {
-                                       info->max_extent =
-                                               btrfs_parse_size(num);
-                                       kfree(num);
-
-                                       info->max_extent = max_t(u64,
-                                                        info->max_extent,
-                                                        root->sectorsize);
-                                       printk("btrfs: max_extent at %Lu\n",
-                                              info->max_extent);
-                               }
+                       num = match_strdup(&args[0]);
+                       if (num) {
+                               info->max_extent = btrfs_parse_size(num);
+                               kfree(num);
+
+                               info->max_extent = max_t(u64,
+                                       info->max_extent, root->sectorsize);
+                               printk(KERN_INFO "btrfs: max_extent at %llu\n",
+                                      info->max_extent);
                        }
                        break;
                case Opt_max_inline:
-                       if (info) {
-                               char *num = match_strdup(&args[0]);
-                               if (num) {
-                                       info->max_inline =
-                                               btrfs_parse_size(num);
-                                       kfree(num);
-
-                                       info->max_inline = max_t(u64,
-                                                        info->max_inline,
-                                                        root->sectorsize);
-                                       printk("btrfs: max_inline at %Lu\n",
-                                              info->max_inline);
-                               }
+                       num = match_strdup(&args[0]);
+                       if (num) {
+                               info->max_inline = btrfs_parse_size(num);
+                               kfree(num);
+
+                               info->max_inline = max_t(u64,
+                                       info->max_inline, root->sectorsize);
+                               printk(KERN_INFO "btrfs: max_inline at %llu\n",
+                                       info->max_inline);
                        }
                        break;
                case Opt_alloc_start:
-                       if (info) {
-                               char *num = match_strdup(&args[0]);
-                               if (num) {
-                                       info->alloc_start =
-                                               btrfs_parse_size(num);
-                                       kfree(num);
-                                       printk("btrfs: allocations start at "
-                                              "%Lu\n", info->alloc_start);
-                               }
+                       num = match_strdup(&args[0]);
+                       if (num) {
+                               info->alloc_start = btrfs_parse_size(num);
+                               kfree(num);
+                               printk(KERN_INFO
+                                       "btrfs: allocations start at %llu\n",
+                                       info->alloc_start);
                        }
                        break;
                default:
@@ -221,7 +203,61 @@ int btrfs_parse_options(char *options, struct btrfs_root *root,
                }
        }
        kfree(options);
-       return 1;
+       return 0;
+}
+
+/*
+ * Parse mount options that are required early in the mount process.
+ *
+ * All other options will be parsed on much later in the mount process and
+ * only when we need to allocate a new super block.
+ */
+static int btrfs_parse_early_options(const char *options,
+                       char **subvol_name)
+{
+       substring_t args[MAX_OPT_ARGS];
+       char *opts, *p;
+       int error = 0;
+
+       if (!options)
+               goto out;
+
+       /*
+        * strsep changes the string, duplicate it because parse_options
+        * gets called twice
+        */
+       opts = kstrdup(options, GFP_KERNEL);
+       if (!opts)
+               return -ENOMEM;
+
+       while ((p = strsep(&opts, ",")) != NULL) {
+               int token;
+               if (!*p)
+                       continue;
+
+               token = match_token(p, tokens, args);
+               switch (token) {
+               case Opt_subvol:
+                       *subvol_name = match_strdup(&args[0]);
+                       break;
+               default:
+                       break;
+               }
+       }
+
+       kfree(opts);
+ out:
+       /*
+        * If no subvolume name is specified we use the default one.  Allocate
+        * a copy of the string "default" here so that code later in the
+        * mount path doesn't care if it's the default volume or another one.
+        */
+       if (!*subvol_name) {
+               *subvol_name = kstrdup("default", GFP_KERNEL);
+               if (!*subvol_name)
+                       return -ENOMEM;
+       }
+       return error;
 }
 
 static int btrfs_fill_super(struct super_block * sb,
@@ -328,23 +364,33 @@ static int btrfs_test_super(struct super_block *s, void *data)
        return root->fs_info->fs_devices == test_fs_devices;
 }
 
-int btrfs_get_sb_bdev(struct file_system_type *fs_type,
-       int flags, const char *dev_name, void *data,
-       struct vfsmount *mnt, const char *subvol)
+/*
+ * Find a superblock for the given device / mount point.
+ *
+ * Note:  This is based on get_sb_bdev from fs/super.c with a few additions
+ *       for multiple device setup.  Make sure to keep it in sync.
+ */
+static int btrfs_get_sb(struct file_system_type *fs_type, int flags,
+               const char *dev_name, void *data, struct vfsmount *mnt)
 {
+       char *subvol_name = NULL;
        struct block_device *bdev = NULL;
        struct super_block *s;
        struct dentry *root;
        struct btrfs_fs_devices *fs_devices = NULL;
        int error = 0;
 
+       error = btrfs_parse_early_options(data, &subvol_name);
+       if (error)
+               goto error;
+
        error = btrfs_scan_one_device(dev_name, flags, fs_type, &fs_devices);
        if (error)
-               return error;
+               goto error_free_subvol_name;
 
        error = btrfs_open_devices(fs_devices, flags, fs_type);
        if (error)
-               return error;
+               goto error_free_subvol_name;
 
        bdev = fs_devices->latest_bdev;
        btrfs_lock_volumes();
@@ -378,51 +424,36 @@ int btrfs_get_sb_bdev(struct file_system_type *fs_type,
                s->s_flags |= MS_ACTIVE;
        }
 
-       if (subvol) {
-               root = lookup_one_len(subvol, s->s_root, strlen(subvol));
-               if (IS_ERR(root)) {
-                       up_write(&s->s_umount);
-                       deactivate_super(s);
-                       error = PTR_ERR(root);
-                       goto error;
-               }
-               if (!root->d_inode) {
-                       dput(root);
-                       up_write(&s->s_umount);
-                       deactivate_super(s);
-                       error = -ENXIO;
-                       goto error;
-               }
-       } else {
-               root = dget(s->s_root);
+       root = lookup_one_len(subvol_name, s->s_root, strlen(subvol_name));
+       if (IS_ERR(root)) {
+               up_write(&s->s_umount);
+               deactivate_super(s);
+               error = PTR_ERR(root);
+               goto error;
+       }
+       if (!root->d_inode) {
+               dput(root);
+               up_write(&s->s_umount);
+               deactivate_super(s);
+               error = -ENXIO;
+               goto error;
        }
 
        mnt->mnt_sb = s;
        mnt->mnt_root = root;
+
+       kfree(subvol_name);
        return 0;
 
 error_s:
        error = PTR_ERR(s);
 error_bdev:
        btrfs_close_devices(fs_devices);
+error_free_subvol_name:
+       kfree(subvol_name);
 error:
        return error;
 }
-/* end copy & paste */
-
-static int btrfs_get_sb(struct file_system_type *fs_type,
-       int flags, const char *dev_name, void *data, struct vfsmount *mnt)
-{
-       int ret;
-       char *subvol_name = NULL;
-
-       btrfs_parse_options((char *)data, NULL, &subvol_name);
-       ret = btrfs_get_sb_bdev(fs_type, flags, dev_name, data, mnt,
-                       subvol_name ? subvol_name : "default");
-       if (subvol_name)
-               kfree(subvol_name);
-       return ret;
-}
 
 static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {