On 3 January 2014 06:10, Qu Wenruo <quwenruo@xxxxxxxxxxxxxx> wrote:
> Btrfs can be remounted without barrier, but there is no "barrier" option
> so nobody can remount btrfs back with barrier on. Only umount and
> mount again can re-enable barrier.(Quite awkward)
>
> Also the mount options in the document is also changed slightly for the
> further pairing options changes.
>
> Reported-by: Daniel Blueman <daniel@xxxxxxxxx>
> Signed-off-by: Qu Wenruo <quwenruo@xxxxxxxxxxxxxx>
> Cc: David Sterba <dsterba@xxxxxxx>
> ---
> changelog:
> v1: Add barrier option
> v2: Change the document style to fit pairing options better
> ---
> Documentation/filesystems/btrfs.txt | 13 +++++++------
> fs/btrfs/super.c | 8 +++++++-
> 2 files changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/Documentation/filesystems/btrfs.txt b/Documentation/filesystems/btrfs.txt
> index 5dd282d..2d2e016 100644
> --- a/Documentation/filesystems/btrfs.txt
> +++ b/Documentation/filesystems/btrfs.txt
> @@ -38,7 +38,7 @@ Mount Options
> =============
>
> When mounting a btrfs filesystem, the following option are accepted.
> -Unless otherwise specified, all options default to off.
> +Options with (*) are default options and will not show in the mount options.
>
> alloc_start=<bytes>
> Debugging option to force all block allocations above a certain
> @@ -138,12 +138,13 @@ Unless otherwise specified, all options default to off.
> Disable support for Posix Access Control Lists (ACLs). See the
> acl(5) manual page for more information about ACLs.
>
> + barrier(*)
> nobarrier
> - Disables the use of block layer write barriers. Write barriers ensure
> - that certain IOs make it through the device cache and are on persistent
> - storage. If used on a device with a volatile (non-battery-backed)
> - write-back cache, this option will lead to filesystem corruption on a
> - system crash or power loss.
> + Disable/enable the use of block layer write barriers. Write barriers
Please use
"Enable/Disable ..."
to match order on the options barrier(*) then nobarrier immediately above.
> + ensure that certain IOs make it through the device cache and are on
> + persistent storage. If used on a device with a volatile
And:
"... If disabled on a device with a volatile"
to make more sense when both enable and disable options are listed.
> + (non-battery-backed) write-back cache, this option will lead to
> + filesystem corruption on a system crash or power loss.
>
> nodatacow
> Disable data copy-on-write for newly created files. Implies nodatasum,
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index e9c13fb..fe9d8a6 100644
> --- 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_commit_interval, Opt_barrier,
> Opt_err,
> };
>
> @@ -335,6 +335,7 @@ static match_table_t tokens = {
> {Opt_nodatasum, "nodatasum"},
> {Opt_nodatacow, "nodatacow"},
> {Opt_nobarrier, "nobarrier"},
> + {Opt_barrier, "barrier"},
> {Opt_max_inline, "max_inline=%s"},
> {Opt_alloc_start, "alloc_start=%s"},
> {Opt_thread_pool, "thread_pool=%d"},
> @@ -494,6 +495,11 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
> btrfs_clear_opt(info->mount_opt, SSD);
> btrfs_clear_opt(info->mount_opt, SSD_SPREAD);
> break;
> + case Opt_barrier:
> + if (btrfs_test_opt(root, NOBARRIER))
> + btrfs_info(root->fs_info, "turning on barriers");
> + btrfs_clear_opt(info->mount_opt, NOBARRIER);
> + break;
> case Opt_nobarrier:
> btrfs_info(root->fs_info, "turning off barriers");
> btrfs_set_opt(info->mount_opt, NOBARRIER);
> --
> 1.8.5.2
>
Thanks,
Mike
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