[PATCH v6 2/3] btrfs: balance: add args info during start and resume

[Anand Jain <anand.jain@oracle.com>]

Balance arg info is an important information to be reviewed for the
system audit. So this patch adds them to the kernel log.

Example:
->btrfs bal start -f -mprofiles=raid1,convert=single,soft -dlimit=10..20,usage=50 /btrfs

kernel: BTRFS info (device sdb): balance: start -f -dusage=50,limit=10..20 -msoft,profiles=raid1,convert=single -ssoft,profiles=raid1,convert=single

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
v5->v6: Use () in the body for the args sent in defines
	Use right indent to align '\'
	Use goto to out_overflow instead of return (also fixes a mem leak in v5)
	Rename CHECK_UPDATE_BP_XXX to CHECK_APPEND_XXX
v4.1->v5: Per David review comment the code..
           bp += snprintf(bp, buf - bp + size_buf, "soft,");
	  is not safe if 'buf - bp + size_buf' becomes accidentally
	  negative, so fix this by using following snprintf.

 #define CHECK_UPDATE_BP_1(a) \
       do { \
               ret = snprintf(bp, size_bp, a); \
               if (ret < 0 || ret >= size_bp) \
                       goto out; \
               size_bp -= ret; \
               bp += ret; \
       } while (0)

	And initialize the tmp_buf to null.

v4->v4.1: Rename last missed sz to size_buf.

v3->v4: Change log updated with new example.
	Log format is changed to almost match with the cli.
	snprintf drop %s for inline string.
	Print range as =%u..%u instead of min=%umax=%u.
	soft is under the args now.
	force is printed as -f.

v2->v3: Change log updated.
        Make use of describe_block_group() added in 1/4
        Drop using strcat instead use snprintf.
        Logs string format updated as shown in the example above.

v1->v2: Change log update.
        Move adding the logs for balance complete and end to a new patch

 fs/btrfs/volumes.c | 163 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 160 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 3ab22e7e404e..eb18739f19ef 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3757,6 +3757,164 @@ static inline int validate_convert_profile(struct btrfs_balance_args *bctl_arg,
 		 (bctl_arg->target & ~allowed)));
 }
 
+static void describe_balance_args(struct btrfs_balance_args *bargs, char *buf,
+				 u32 size_buf)
+{
+	int ret;
+	u32 size_bp = size_buf;
+	char *bp = buf;
+	u64 flags = bargs->flags;
+	char tmp_buf[128] = {'\0'};
+
+	if (!flags)
+		return;
+
+#define CHECK_APPEND_NOARG(a)				\
+	do {						\
+		ret = snprintf(bp, size_bp, (a));	\
+		if (ret < 0 || ret >= size_bp)		\
+			goto out_overflow;		\
+		size_bp -= ret;				\
+		bp += ret;				\
+	} while (0)
+
+#define CHECK_APPEND_1ARG(a, v1)			\
+	do {						\
+		ret = snprintf(bp, size_bp, (a), (v1));	\
+		if (ret < 0 || ret >= size_bp)		\
+			goto out_overflow;		\
+		size_bp -= ret;				\
+		bp += ret;				\
+	} while (0)
+
+#define CHECK_APPEND_2ARG(a, v1, v2)				\
+	do {							\
+		ret = snprintf(bp, size_bp, (a), (v1), (v2));	\
+		if (ret < 0 || ret >= size_bp)			\
+			goto out_overflow;			\
+		size_bp -= ret;					\
+		bp += ret;					\
+	} while (0)
+
+	if (flags & BTRFS_BALANCE_ARGS_SOFT)
+		CHECK_APPEND_NOARG("soft,");
+
+	if (flags & BTRFS_BALANCE_ARGS_PROFILES) {
+		btrfs_describe_block_groups(bargs->profiles, tmp_buf,
+					    sizeof(tmp_buf));
+		CHECK_APPEND_1ARG("profiles=%s,", tmp_buf);
+	}
+
+	if (flags & BTRFS_BALANCE_ARGS_USAGE)
+		CHECK_APPEND_1ARG("usage=%llu,", bargs->usage);
+
+	if (flags & BTRFS_BALANCE_ARGS_USAGE_RANGE)
+		CHECK_APPEND_2ARG("usage=%u..%u,",
+				  bargs->usage_min, bargs->usage_max);
+
+	if (flags & BTRFS_BALANCE_ARGS_DEVID)
+		CHECK_APPEND_1ARG("devid=%llu,", bargs->devid);
+
+	if (flags & BTRFS_BALANCE_ARGS_DRANGE)
+		CHECK_APPEND_2ARG("drange=%llu..%llu,",
+				  bargs->pstart, bargs->pend);
+
+	if (flags & BTRFS_BALANCE_ARGS_VRANGE)
+		CHECK_APPEND_2ARG("vrange%llu..%llu,",
+				  bargs->vstart, bargs->vend);
+
+	if (flags & BTRFS_BALANCE_ARGS_LIMIT)
+		CHECK_APPEND_1ARG("limit=%llu,", bargs->limit);
+
+	if (flags & BTRFS_BALANCE_ARGS_LIMIT_RANGE)
+		CHECK_APPEND_2ARG("limit=%u..%u,",
+				bargs->limit_min, bargs->limit_max);
+
+	if (flags & BTRFS_BALANCE_ARGS_STRIPES_RANGE)
+		CHECK_APPEND_2ARG("stripes=%u..%u,",
+				  bargs->stripes_min, bargs->stripes_max);
+
+	if (flags & BTRFS_BALANCE_ARGS_CONVERT) {
+		int index = btrfs_bg_flags_to_raid_index(bargs->target);
+
+		CHECK_APPEND_1ARG("convert=%s,", get_raid_name(index));
+	}
+
+out_overflow:
+#undef CHECK_APPEND_2ARG
+#undef CHECK_APPEND_1ARG
+#undef CHECK_APPEND_NOARG
+
+	if (size_bp < size_buf)
+		buf[size_buf - size_bp - 1] = '\0'; /* remove last , */
+	else
+		buf[0] = '\0';
+}
+
+static void describe_balance_start_or_resume(struct btrfs_fs_info *fs_info)
+{
+	u32 size_buf = 1024;
+	char tmp_buf[192] = {'\0'};
+	char *buf;
+	char *bp;
+	u32 size_bp = size_buf;
+	int ret;
+	struct btrfs_balance_control *bctl = fs_info->balance_ctl;
+
+	buf = kzalloc(size_buf, GFP_KERNEL);
+	if (!buf)
+		return;
+
+	bp = buf;
+#define CHECK_APPEND_NOARG(a)				\
+	do {						\
+		ret = snprintf(bp, size_bp, (a));	\
+		if (ret < 0 || ret >= size_bp)		\
+			goto out_overflow;		\
+		size_bp -= ret;				\
+		bp += ret;				\
+	} while (0)
+
+#define CHECK_APPEND_1ARG(a, v1)			\
+	do {						\
+		ret = snprintf(bp, size_bp, (a), (v1));	\
+		if (ret < 0 || ret >= size_bp)		\
+			goto out_overflow;		\
+		size_bp -= ret;				\
+		bp += ret;				\
+	} while (0)
+
+	if (bctl->flags & BTRFS_BALANCE_FORCE)
+		CHECK_APPEND_NOARG("-f ");
+
+	if (bctl->flags & BTRFS_BALANCE_DATA) {
+		describe_balance_args(&bctl->data, tmp_buf, sizeof(tmp_buf));
+		CHECK_APPEND_1ARG("-d%s ", tmp_buf);
+	}
+
+	if (bctl->flags & BTRFS_BALANCE_METADATA) {
+		describe_balance_args(&bctl->meta, tmp_buf, sizeof(tmp_buf));
+		CHECK_APPEND_1ARG("-m%s ", tmp_buf);
+	}
+
+	if (bctl->flags & BTRFS_BALANCE_SYSTEM) {
+		describe_balance_args(&bctl->sys, tmp_buf, sizeof(tmp_buf));
+		CHECK_APPEND_1ARG("-s%s ", tmp_buf);
+	}
+
+out_overflow:
+#undef CHECK_APPEND_1ARG
+#undef CHECK_APPEND_NOARG
+
+	if (size_bp < size_buf)
+		buf[size_buf - size_bp - 1] = '\0'; /* remove last " "*/
+	btrfs_info(fs_info, "%s %s",
+		   bctl->flags & BTRFS_BALANCE_RESUME ?
+		   "balance: resume":"balance: start", buf);
+
+	kfree(buf);
+}
+
 /*
  * Should be called with balance mutexe held
  */
@@ -3896,6 +4054,7 @@ int btrfs_balance(struct btrfs_fs_info *fs_info,
 
 	ASSERT(!test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));
 	set_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags);
+	describe_balance_start_or_resume(fs_info);
 	mutex_unlock(&fs_info->balance_mutex);
 
 	ret = __btrfs_balance(fs_info);
@@ -3933,10 +4092,8 @@ static int balance_kthread(void *data)
 	int ret = 0;
 
 	mutex_lock(&fs_info->balance_mutex);
-	if (fs_info->balance_ctl) {
-		btrfs_info(fs_info, "balance: resuming");
+	if (fs_info->balance_ctl)
 		ret = btrfs_balance(fs_info, fs_info->balance_ctl, NULL);
-	}
 	mutex_unlock(&fs_info->balance_mutex);
 
 	return ret;
-- 
1.8.3.1