btrfs: Add nodiscard mount option.

Add nodiscard mount option to disable discard with remount option.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/Documentation/filesystems/btrfs.txt b/Documentation/filesystems/btrfs.txt
index e87609a..7254cf5 100644 (file)
--- a/Documentation/filesystems/btrfs.txt
+++ b/Documentation/filesystems/btrfs.txt
@@ -98,9 +98,12 @@ Options with (*) are default options and will not show in the mount options.
        can be avoided.  Especially useful when trying to mount a multi-device
        setup as root.  May be specified multiple times for multiple devices.
 
+  nodiscard(*)
   discard
-       Issue frequent commands to let the block device reclaim space freed by
-       the filesystem.  This is useful for SSD devices, thinly provisioned
+       Disable/enable discard mount option.
+       Discard issues frequent commands to let the block device reclaim space
+       freed by the filesystem.
+       This is useful for SSD devices, thinly provisioned
        LUNs and virtual machine images, but may have a significant
        performance impact.  (The fstrim command is also available to
        initiate batch trims from userspace).

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 44513f3..e153770 100644 (file)
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -323,7 +323,7 @@ enum {
        Opt_no_space_cache, Opt_recovery, Opt_skip_balance,
        Opt_check_integrity, Opt_check_integrity_including_extent_data,
        Opt_check_integrity_print_mask, Opt_fatal_errors, Opt_rescan_uuid_tree,
-       Opt_commit_interval, Opt_barrier, Opt_nodefrag,
+       Opt_commit_interval, Opt_barrier, Opt_nodefrag, Opt_nodiscard,
        Opt_err,
 };
 
@@ -351,6 +351,7 @@ static match_table_t tokens = {
        {Opt_flushoncommit, "flushoncommit"},
        {Opt_ratio, "metadata_ratio=%d"},
        {Opt_discard, "discard"},
+       {Opt_nodiscard, "nodiscard"},
        {Opt_space_cache, "space_cache"},
        {Opt_clear_cache, "clear_cache"},
        {Opt_user_subvol_rm_allowed, "user_subvol_rm_allowed"},
@@ -575,6 +576,9 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
                case Opt_discard:
                        btrfs_set_opt(info->mount_opt, DISCARD);
                        break;
+               case Opt_nodiscard:
+                       btrfs_clear_opt(info->mount_opt, DISCARD);
+                       break;
                case Opt_space_cache:
                        btrfs_set_opt(info->mount_opt, SPACE_CACHE);
                        break;