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Commit aac1a3c7 authored by Steven Whitehouse's avatar Steven Whitehouse
Browse files

[GFS2] Add a comment about reading the super block 



The comment explains why we use the bio functions to read
the super block.

Signed-off-by: default avatarSteven Whitehouse <swhiteho@redhat.com>
Cc: Andrew Morton <akpm@osdl.org>
Cc: Srinivasa Ds <srinivasa@in.ibm.com>
parent 0da3585e

fs/gfs2/super.c

+18 −0
Original line number Diff line number Diff line
@@ -180,6 +180,24 @@ static int end_bio_io_page(struct bio *bio, unsigned int bytes_done, int error) 
	return 0;

}



/**

 * gfs2_read_super - Read the gfs2 super block from disk

 * @sb: The VFS super block

 * @sector: The location of the super block

 *

 * This uses the bio functions to read the super block from disk

 * because we want to be 100% sure that we never read cached data.

 * A super block is read twice only during each GFS2 mount and is

 * never written to by the filesystem. The first time its read no

 * locks are held, and the only details which are looked at are those

 * relating to the locking protocol. Once locking is up and working,

 * the sb is read again under the lock to establish the location of

 * the master directory (contains pointers to journals etc) and the

 * root directory.

 *

 * Returns: A page containing the sb or NULL

 */



struct page *gfs2_read_super(struct super_block *sb, sector_t sector)

{

	struct page *page;