GFS2: Clean up log write code path

Prior to this patch, we have two ways of sending i/o to the log.
One of those is used when we need to allocate both the data
to be written itself and also a buffer head to submit it. This
is done via sb_getblk and friends. This is used mostly for writing
log headers.

The other method is used when writing blocks which have some
in-place counterpart. This is the case for all the metadata
blocks which are journalled, and when journaled data is in use,
for unescaped journalled data blocks.

This patch replaces both of those two methods, and about half
a dozen separate i/o submission points with a single i/o
submission function. We also go direct to bio rather than
using buffer heads, since this allows us to build i/o
requests of the maximum size for the block device in
question. It also reduces the memory required for flushing
the log, which can be very useful in low memory situations.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/gfs2/lops.h b/fs/gfs2/lops.h
index 3c0b2737658a..825356d9dc14 100644
--- a/fs/gfs2/lops.h
+++ b/fs/gfs2/lops.h
@@ -27,6 +27,8 @@ extern const struct gfs2_log_operations gfs2_rg_lops;
 extern const struct gfs2_log_operations gfs2_databuf_lops;
 
 extern const struct gfs2_log_operations *gfs2_log_ops[];
+extern void gfs2_log_write_page(struct gfs2_sbd *sdp, struct page *page);
+extern void gfs2_log_flush_bio(struct gfs2_sbd *sdp, int rw);
 
 static inline unsigned int buf_limit(struct gfs2_sbd *sdp)
 {