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Commit 842bef58 authored by Qu Wenruo's avatar Qu Wenruo Committed by Chris Mason
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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: default avatarDaniel Blueman <daniel@quora.org>
Signed-off-by: default avatarQu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: default avatarMike Fleetwood <mike.fleetwood@googlemail.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.cz>
Signed-off-by: default avatarJosef Bacik <jbacik@fb.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent e8117c26

Documentation/filesystems/btrfs.txt

+7 −6
Original line number Diff line number Diff line
@@ -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,

fs/btrfs/super.c

+7 −1
Original line number Diff line number Diff line
@@ -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);