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btrfs: Add "barrier" option to support "-o remount,barrier" 

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@quora.org>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Mike Fleetwood <mike.fleetwood@googlemail.com>
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
This commit is contained in:
Qu Wenruo 2014-01-06 09:58:25 +08:00 committed by Chris Mason
parent e8117c26b2
commit 842bef5891
2 changed files with 14 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
Documentation/filesystems/btrfs.txt
View File

@ -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.
Enable/disable 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 disabled on a device with a volatile
(non-battery-backed) write-back cache, nobarrier 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,

8
fs/btrfs/super.c
View File

@ -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);