btrfs: Introduce new mount option to disable tree log replay

Introduce a new mount option "nologreplay" to co-operate with "ro" mount
option to get real readonly mount, like "norecovery" in ext* and xfs.

Since the new parse_options() need to check new flags at remount time,
so add a new parameter for parse_options().

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Reviewed-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Tested-by: Austin S. Hemmelgarn <ahferroin7@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/Documentation/filesystems/btrfs.txt b/Documentation/filesystems/btrfs.txt
index a2b1c50..6593d2e 100644 (file)
--- a/Documentation/filesystems/btrfs.txt
+++ b/Documentation/filesystems/btrfs.txt
@@ -168,6 +168,14 @@ Options with (*) are default options and will not show in the mount options.
   notreelog
        Enable/disable the tree logging used for fsync and O_SYNC writes.
 
+  nologreplay
+       Disable the log tree replay at mount time to prevent filesystem
+       from getting modified.
+       Must be used with 'ro' mount option.
+       A filesystem mounted with this option cannot transition to a
+       read-write mount via remount,rw - the filesystem must be unmounted
+       and mounted back again if read-write access is desired.
+
   usebackuproot
        Enable attempts to use backup tree roots if a bad tree root is found at
        mount time.

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index e39eeb9..a79bb73 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2250,6 +2250,7 @@ struct btrfs_ioctl_defrag_range_args {
 #define BTRFS_MOUNT_FRAGMENT_DATA      (1 << 24)
 #define BTRFS_MOUNT_FRAGMENT_METADATA  (1 << 25)
 #define BTRFS_MOUNT_FREE_SPACE_TREE    (1 << 26)
+#define BTRFS_MOUNT_NOLOGREPLAY                (1 << 27)
 
 #define BTRFS_DEFAULT_COMMIT_INTERVAL  (30)
 #define BTRFS_DEFAULT_MAX_INLINE       (8192)
@@ -4151,7 +4152,8 @@ void btrfs_sysfs_remove_mounted(struct btrfs_fs_info *fs_info);
 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size);
 
 /* super.c */
-int btrfs_parse_options(struct btrfs_root *root, char *options);
+int btrfs_parse_options(struct btrfs_root *root, char *options,
+                       unsigned long new_flags);
 int btrfs_sync_fs(struct super_block *sb, int wait);
 
 #ifdef CONFIG_PRINTK

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index c036362..18541dc 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2750,7 +2750,7 @@ int open_ctree(struct super_block *sb,
         */
        fs_info->compress_type = BTRFS_COMPRESS_ZLIB;
 
-       ret = btrfs_parse_options(tree_root, options);
+       ret = btrfs_parse_options(tree_root, options, sb->s_flags);
        if (ret) {
                err = ret;
                goto fail_alloc;
@@ -3029,8 +3029,9 @@ retry_root_backup:
        if (ret)
                goto fail_trans_kthread;
 
-       /* do not make disk changes in broken FS */
-       if (btrfs_super_log_root(disk_super) != 0) {
+       /* do not make disk changes in broken FS or nologreplay is given */
+       if (btrfs_super_log_root(disk_super) != 0 &&
+           !btrfs_test_opt(tree_root, NOLOGREPLAY)) {
                ret = btrfs_replay_log(fs_info, fs_devices);
                if (ret) {
                        err = ret;

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 7ed3863..e8a7a9f 100644 (file)
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -304,6 +304,7 @@ enum {
        Opt_commit_interval, Opt_barrier, Opt_nodefrag, Opt_nodiscard,
        Opt_noenospc_debug, Opt_noflushoncommit, Opt_acl, Opt_datacow,
        Opt_datasum, Opt_treelog, Opt_noinode_cache, Opt_usebackuproot,
+       Opt_nologreplay,
 #ifdef CONFIG_BTRFS_DEBUG
        Opt_fragment_data, Opt_fragment_metadata, Opt_fragment_all,
 #endif
@@ -335,6 +336,7 @@ static const match_table_t tokens = {
        {Opt_noacl, "noacl"},
        {Opt_notreelog, "notreelog"},
        {Opt_treelog, "treelog"},
+       {Opt_nologreplay, "nologreplay"},
        {Opt_flushoncommit, "flushoncommit"},
        {Opt_noflushoncommit, "noflushoncommit"},
        {Opt_ratio, "metadata_ratio=%d"},
@@ -374,7 +376,8 @@ static const match_table_t tokens = {
  * reading in a new superblock is parsed here.
  * XXX JDM: This needs to be cleaned up for remount.
  */
-int btrfs_parse_options(struct btrfs_root *root, char *options)
+int btrfs_parse_options(struct btrfs_root *root, char *options,
+                       unsigned long new_flags)
 {
        struct btrfs_fs_info *info = root->fs_info;
        substring_t args[MAX_OPT_ARGS];
@@ -394,8 +397,12 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
        else if (cache_gen)
                btrfs_set_opt(info->mount_opt, SPACE_CACHE);
 
+       /*
+        * Even the options are empty, we still need to do extra check
+        * against new flags
+        */
        if (!options)
-               goto out;
+               goto check;
 
        /*
         * strsep changes the string, duplicate it because parse_options
@@ -607,6 +614,10 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
                        btrfs_clear_and_info(root, NOTREELOG,
                                             "enabling tree log");
                        break;
+               case Opt_nologreplay:
+                       btrfs_set_and_info(root, NOLOGREPLAY,
+                                          "disabling log replay at mount time");
+                       break;
                case Opt_flushoncommit:
                        btrfs_set_and_info(root, FLUSHONCOMMIT,
                                           "turning on flush-on-commit");
@@ -797,6 +808,15 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
                        break;
                }
        }
+check:
+       /*
+        * Extra check for current option against current flag
+        */
+       if (btrfs_test_opt(root, NOLOGREPLAY) && !(new_flags & MS_RDONLY)) {
+               btrfs_err(root->fs_info,
+                         "nologreplay must be used with ro mount option");
+               ret = -EINVAL;
+       }
 out:
        if (btrfs_fs_compat_ro(root->fs_info, FREE_SPACE_TREE) &&
            !btrfs_test_opt(root, FREE_SPACE_TREE) &&
@@ -1207,6 +1227,8 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
                seq_puts(seq, ",ssd");
        if (btrfs_test_opt(root, NOTREELOG))
                seq_puts(seq, ",notreelog");
+       if (btrfs_test_opt(root, NOLOGREPLAY))
+               seq_puts(seq, ",nologreplay");
        if (btrfs_test_opt(root, FLUSHONCOMMIT))
                seq_puts(seq, ",flushoncommit");
        if (btrfs_test_opt(root, DISCARD))
@@ -1688,7 +1710,7 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
                }
        }
 
-       ret = btrfs_parse_options(root, data);
+       ret = btrfs_parse_options(root, data, *flags);
        if (ret) {
                ret = -EINVAL;
                goto restore;