[PATCH] btrfs: Implement warning for commit values exceeding 300

[sawara04.o@gmail.com]

From: Kyoji Ogasawara <sawara04.o@gmail.com>

The Btrfs documentation states that if the commit value is greater than 300
a warning should be issued. This commit implements that functionality.
For more details, visit:
https://btrfs.readthedocs.io/en/latest/Administration.html#btrfs-specific-mount-options

Signed-off-by: Kyoji Ogasawara <sawara04.o@gmail.com>
---
 fs/btrfs/fs.h    | 1 +
 fs/btrfs/super.c | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/fs/btrfs/fs.h b/fs/btrfs/fs.h
index b572d6b9730b..f46fba127caa 100644
--- a/fs/btrfs/fs.h
+++ b/fs/btrfs/fs.h
@@ -285,6 +285,7 @@ enum {
 #define BTRFS_FEATURE_INCOMPAT_SAFE_CLEAR		0ULL
 
 #define BTRFS_DEFAULT_COMMIT_INTERVAL	(30)
+#define BTRFS_WARNING_COMMIT_INTERVAL	(300)
 #define BTRFS_DEFAULT_MAX_INLINE	(2048)
 
 struct btrfs_dev_replace {
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index dc4fee519ca6..c6911e9f17f2 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -569,6 +569,12 @@ static int btrfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 		break;
 	case Opt_commit_interval:
 		ctx->commit_interval = result.uint_32;
+		if (ctx->commit_interval > BTRFS_WARNING_COMMIT_INTERVAL) {
+			btrfs_warn(NULL,
+"commit=%u is considerably high (> %u). Large amount of data can be lost when the system crashes.",
+				ctx->commit_interval,
+				BTRFS_WARNING_COMMIT_INTERVAL);
+		}
 		if (ctx->commit_interval == 0)
 			ctx->commit_interval = BTRFS_DEFAULT_COMMIT_INTERVAL;
 		break;
-- 
2.47.0