On 3 January 2014 06:10, Qu Wenruo <quwen...@cn.fujitsu.com> 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 <dan...@quora.org> > Signed-off-by: Qu Wenruo <quwen...@cn.fujitsu.com> > Cc: David Sterba <dste...@suse.cz> > --- > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html