block: Add vfs_msg() interface

In preparation of moving DAX capability checks to the block layer
from filesystem code, add a VFS message interface that aligns with
filesystem's message format.

For instance, a vfs_msg() message followed by XFS messages in case
of a dax mount error may look like:

  VFS (pmem0p1): error: unaligned partition for dax
  XFS (pmem0p1): DAX unsupported by block device. Turning off DAX.
  XFS (pmem0p1): Mounting V5 Filesystem
   :

vfs_msg() is largely based on ext4_msg().

Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <axboe@fb.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Boaz Harrosh <boaz@plexistor.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>

diff --git a/fs/block_dev.c b/fs/block_dev.c
index b25bb23..91e0ec0 100644 (file)
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -50,6 +50,18 @@ struct block_device *I_BDEV(struct inode *inode)
 }
 EXPORT_SYMBOL(I_BDEV);
 
+void __vfs_msg(struct super_block *sb, const char *prefix, const char *fmt, ...)
+{
+       struct va_format vaf;
+       va_list args;
+
+       va_start(args, fmt);
+       vaf.fmt = fmt;
+       vaf.va = &args;
+       printk_ratelimited("%sVFS (%s): %pV\n", prefix, sb->s_id, &vaf);
+       va_end(args);
+}
+
 static void bdev_write_inode(struct block_device *bdev)
 {
        struct inode *inode = bdev->bd_inode;

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 669e419..78c48ab 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -767,6 +767,17 @@ static inline void rq_flush_dcache_pages(struct request *rq)
 }
 #endif
 
+#ifdef CONFIG_PRINTK
+#define vfs_msg(sb, level, fmt, ...)                           \
+       __vfs_msg(sb, level, fmt, ##__VA_ARGS__)
+#else
+#define vfs_msg(sb, level, fmt, ...)                           \
+do {                                                           \
+       no_printk(fmt, ##__VA_ARGS__);                          \
+       __vfs_msg(sb, "", " ");                                 \
+} while (0)
+#endif
+
 extern int blk_register_queue(struct gendisk *disk);
 extern void blk_unregister_queue(struct gendisk *disk);
 extern blk_qc_t generic_make_request(struct bio *bio);