btrfs: add mount option to set commit interval

I'ts hardcoded to 30 seconds which is fine for most users. Higher values
defer data being synced to permanent storage with obvious consequences
when the system crashes. The upper bound is not forced, but a warning is
printed if it's more than 300 seconds (5 minutes).

Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 2cc5b80eeae9..196790375bb3 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -321,6 +321,7 @@ 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_commit_interval,
         Opt_err,
 };
 
@@ -361,6 +362,7 @@ static match_table_t tokens = {
         {Opt_check_integrity_including_extent_data, "check_int_data"},
         {Opt_check_integrity_print_mask, "check_int_print_mask=%d"},
         {Opt_fatal_errors, "fatal_errors=%s"},
+        {Opt_commit_interval, "commit=%d"},
         {Opt_err, NULL},
 };
 
@@ -645,6 +647,29 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
                                 goto out;
                         }
                         break;
+                case Opt_commit_interval:
+                        intarg = 0;
+                        ret = match_int(&args[0], &intarg);
+                        if (ret < 0) {
+                                printk(KERN_ERR
+                                        "btrfs: invalid commit interval\n");
+                                ret = -EINVAL;
+                                goto out;
+                        }
+                        if (intarg > 0) {
+                                if (intarg > 300) {
+                                        printk(KERN_WARNING
+                                            "btrfs: excessive commit interval %d\n",
+                                                        intarg);
+                                }
+                                info->commit_interval = intarg;
+                        } else {
+                                printk(KERN_INFO
+                                    "btrfs: using default commit interval %ds\n",
+                                    BTRFS_DEFAULT_COMMIT_INTERVAL);
+                                info->commit_interval = BTRFS_DEFAULT_COMMIT_INTERVAL;
+                        }
+                        break;
                 case Opt_err:
                         printk(KERN_INFO "btrfs: unrecognized mount option "
                                "'%s'\n", p);
@@ -981,6 +1006,8 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
                                 info->metadata_ratio);
         if (btrfs_test_opt(root, PANIC_ON_FATAL_ERROR))
                 seq_puts(seq, ",fatal_errors=panic");
+        if (info->commit_interval != BTRFS_DEFAULT_COMMIT_INTERVAL)
+                seq_printf(seq, ",commit=%d", info->commit_interval);
         return 0;
 }