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[GFS2] Add a comment about reading the super block

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

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Andrew Morton <akpm@osdl.org>
Cc: Srinivasa Ds <srinivasa@in.ibm.com>
This commit is contained in:
Steven Whitehouse 2006-11-30 10:02:19 -05:00
parent 0da3585e1e
commit aac1a3c77a
1 changed files with 18 additions and 0 deletions
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18
fs/gfs2/super.c
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@ -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;