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authorSteven Whitehouse <swhiteho@redhat.com>2006-11-30 10:02:19 -0500
committerSteven Whitehouse <swhiteho@redhat.com>2006-11-30 10:37:40 -0500
commitaac1a3c77a46c2d06f297641760dd740ac2a84af (patch)
treed56f7891ece4ccbd72dd2a86ed1f613f8a302e0c
parent0da3585e1ef650d3224b4d6f9799558d1d99fa1e (diff)
[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: Steven Whitehouse <swhiteho@redhat.com> Cc: Andrew Morton <akpm@osdl.org> Cc: Srinivasa Ds <srinivasa@in.ibm.com>
-rw-r--r--fs/gfs2/super.c18
1 files changed, 18 insertions, 0 deletions
diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index 3b227274279..43a24f2e590 100644
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -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;