Btrfs: Add mount option to turn off data cow
A number of workloads do not require copy on write data or checksumming.
mount -o nodatasum to disable checksums and -o nodatacow to disable
both copy on write and checksumming.
In nodatacow mode, copy on write is still performed when a given extent
is under snapshot.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index ad4f280..2116728 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -61,12 +61,13 @@
}
enum {
- Opt_subvol, Opt_nodatasum, Opt_err,
+ Opt_subvol, Opt_nodatasum, Opt_nodatacow, Opt_err,
};
static match_table_t tokens = {
{Opt_subvol, "subvol=%s"},
{Opt_nodatasum, "nodatasum"},
+ {Opt_nodatacow, "nodatacow"},
{Opt_err, NULL}
};
@@ -78,12 +79,20 @@
struct btrfs_fs_info *info = NULL;
substring_t args[MAX_OPT_ARGS];
- if (root)
- info = root->fs_info;
-
if (!options)
return 1;
+ /*
+ * strsep changes the string, duplicate it because parse_options
+ * gets called twice
+ */
+ options = kstrdup(options, GFP_NOFS);
+ if (!options)
+ return -ENOMEM;
+
+ if (root)
+ info = root->fs_info;
+
while ((p = strsep (&options, ",")) != NULL) {
int token;
if (!*p)
@@ -92,17 +101,28 @@
token = match_token(p, tokens, args);
switch (token) {
case Opt_subvol:
- if (subvol_name)
+ if (subvol_name) {
*subvol_name = match_strdup(&args[0]);
+ }
break;
case Opt_nodatasum:
- if (root)
+ if (info) {
+ printk("btrfs: setting nodatacsum\n");
btrfs_set_opt(info->mount_opt, NODATASUM);
+ }
+ break;
+ case Opt_nodatacow:
+ if (info) {
+ printk("btrfs: setting nodatacow\n");
+ btrfs_set_opt(info->mount_opt, NODATACOW);
+ btrfs_set_opt(info->mount_opt, NODATASUM);
+ }
break;
default:
- return 0;
+ break;
}
}
+ kfree(options);
return 1;
}