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>
Signed-off-by: Mike Fleetwood <mike.fleetw...@googlemail.com>
Reviewed-by: David Sterba <dste...@suse.cz>
---
Changelog:
v1: Add barrier option
v2: Document style change
v3: Small description change
---
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..ce487a2 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.
+ 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,
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
--
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