On 14/1/20 2:54 PM, Qu Wenruo wrote:
On 2020/1/14 下午2:09, Anand Jain wrote:
The first argument to btrfs_printk() wrappers such as
btrfs_warn_in_rcu(), btrfs_info_in_rcu(), etc.. is fs_info, but in some
context like scan and assembling of the volumes there isn't fs_info yet,
so those code generally don't use the btrfs_printk() wrappers and it
could could still use NULL but then it would become hard to distinguish
whether fs_info is NULL for genuine reason or a bug.
So introduce a define NO_FS_INFO to be used instead of NULL so that we
know the code where fs_info isn't initialized and also we have a
consistent logging functions. Thanks.
I'm not sure why this is needed.
Could you give me an example in which NULL is not clear enough?
The first argument in btrfs_info_in_rcu() can be NULL like for example..
btrfs_info_in_rcu(NULL, ..) which then it shall print the prefix..
BTRFS info (device <unknown>):
Lets say due to some bug local copy of the variable fs_info wasn't
initialized then we end up printing the same unknown <unknown>.
So in the context of device_list_add() as there is no fs_info
genuinely and be different from unknown we use
btrfs_info_in_rcu(NO_FS_INFO, ..) to get prefix something like..
BTRFS info (device ...):
Thanks, Anand
Thanks,
Qu
Suggested-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
---
fs/btrfs/ctree.h | 5 +++++
fs/btrfs/super.c | 14 +++++++++++---
2 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 569931dd0ce5..625c7eee3d0f 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -110,6 +110,11 @@ struct btrfs_ref;
#define BTRFS_STAT_CURR 0
#define BTRFS_STAT_PREV 1
+/*
+ * Used when we know that fs_info is not yet initialized.
+ */
+#define NO_FS_INFO ((void *)0x1)
+
/*
* Count how many BTRFS_MAX_EXTENT_SIZE cover the @size
*/
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index a906315efd19..5bd8a889fed0 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -216,9 +216,17 @@ void __cold btrfs_printk(const struct btrfs_fs_info *fs_info, const char *fmt, .
vaf.fmt = fmt;
vaf.va = &args;
- if (__ratelimit(ratelimit))
- printk("%sBTRFS %s (device %s): %pV\n", lvl, type,
- fs_info ? fs_info->sb->s_id : "<unknown>", &vaf);
+ if (__ratelimit(ratelimit)) {
+ if (fs_info == NULL)
+ printk("%sBTRFS %s (device %s): %pV\n", lvl, type,
+ "<unknown>", &vaf);
+ else if (fs_info == NO_FS_INFO)
+ printk("%sBTRFS %s (device %s): %pV\n", lvl, type,
+ "...", &vaf);
+ else
+ printk("%sBTRFS %s (device %s): %pV\n", lvl, type,
+ fs_info->sb->s_id, &vaf);
+ }
va_end(args);
}
