[GFS2] Tidy up meta_io code

Fix a bug in the directory reading code, where we might have dereferenced
a NULL pointer in case of OOM. Updated the directory code to use the new
& improved version of gfs2_meta_ra() which now returns the first block
that was being read. Previously it was releasing it requiring following
code to grab the block again at each point it was called.

Also turned off readahead on directory lookups since we are reading a
hash table, and therefore reading the entries in order is very
unlikely. Readahead is still used for all other calls to the
directory reading function (e.g. when growing the hash table).

Removed the DIO_START constant. Everywhere this was used, it was
used to unconditionally start i/o aside from a couple of places, so
I've removed it and made the couple of exceptions to this rule into
separate functions.

Also hunted through the other DIO flags and removed them as arguments
from functions which were always called with the same combination of
arguments.

Updated gfs2_meta_indirect_buffer to be a bit more efficient and
hopefully also be a bit easier to read.

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

1 files changed, 30 insertions, 25 deletions

diff --git a/fs/gfs2/glops.c b/fs/gfs2/glops.c
index 9c046db..ef1492e 100644
--- a/fs/gfs2/glops.c
+++ b/fs/gfs2/glops.c
@@ -77,32 +77,24 @@ static void gfs2_page_inval(struct gfs2_glock *gl)
 }
 
 /**
- * gfs2_page_sync - Sync the data pages (not metadata) associated with a glock
+ * gfs2_page_wait - Wait for writeback of data
  * @gl: the glock
- * @flags: DIO_START | DIO_WAIT
  *
  * Syncs data (not metadata) for a regular file.
  * No-op for all other types.
  */
 
-static void gfs2_page_sync(struct gfs2_glock *gl, int flags)
+static void gfs2_page_wait(struct gfs2_glock *gl)
 {
-	struct gfs2_inode *ip;
-	struct inode *inode;
-	struct address_space *mapping;
-	int error = 0;
+	struct gfs2_inode *ip = gl->gl_object;
+	struct inode *inode = &ip->i_inode;
+	struct address_space *mapping = inode->i_mapping;
+	int error;
 
-	ip = gl->gl_object;
-	inode = &ip->i_inode;
-	if (!ip || !S_ISREG(ip->i_di.di_mode))
+	if (!S_ISREG(ip->i_di.di_mode))
 		return;
 
-	mapping = inode->i_mapping;
-
-	if (flags & DIO_START)
-		filemap_fdatawrite(mapping);
-	if (!error && (flags & DIO_WAIT))
-		error = filemap_fdatawait(mapping);
+	error = filemap_fdatawait(mapping);
 
 	/* Put back any errors cleared by filemap_fdatawait()
 	   so they can be caught by someone who can pass them
@@ -115,6 +107,18 @@ static void gfs2_page_sync(struct gfs2_glock *gl, int flags)
 
 }
 
+static void gfs2_page_writeback(struct gfs2_glock *gl)
+{
+	struct gfs2_inode *ip = gl->gl_object;
+	struct inode *inode = &ip->i_inode;
+	struct address_space *mapping = inode->i_mapping;
+
+	if (!S_ISREG(ip->i_di.di_mode))
+		return;
+
+	filemap_fdatawrite(mapping);
+}
+
 /**
  * meta_go_sync - sync out the metadata for this glock
  * @gl: the glock
@@ -132,7 +136,7 @@ static void meta_go_sync(struct gfs2_glock *gl, int flags)
 
 	if (test_and_clear_bit(GLF_DIRTY, &gl->gl_flags)) {
 		gfs2_log_flush(gl->gl_sbd, gl);
-		gfs2_meta_sync(gl, flags | DIO_START | DIO_WAIT);
+		gfs2_meta_sync(gl);
 		if (flags & DIO_RELEASE)
 			gfs2_ail_empty_gl(gl);
 	}
@@ -185,8 +189,7 @@ static void inode_go_xmote_bh(struct gfs2_glock *gl)
 
 	if (gl->gl_state != LM_ST_UNLOCKED &&
 	    (!gh || !(gh->gh_flags & GL_SKIP))) {
-		error = gfs2_meta_read(gl, gl->gl_name.ln_number, DIO_START,
-				       &bh);
+		error = gfs2_meta_read(gl, gl->gl_name.ln_number, 0, &bh);
 		if (!error)
 			brelse(bh);
 	}
@@ -221,16 +224,18 @@ static void inode_go_sync(struct gfs2_glock *gl, int flags)
 
 	if (test_bit(GLF_DIRTY, &gl->gl_flags)) {
 		if (meta && data) {
-			gfs2_page_sync(gl, flags | DIO_START);
+			gfs2_page_writeback(gl);
 			gfs2_log_flush(gl->gl_sbd, gl);
-			gfs2_meta_sync(gl, flags | DIO_START | DIO_WAIT);
-			gfs2_page_sync(gl, flags | DIO_WAIT);
+			gfs2_meta_sync(gl);
+			gfs2_page_wait(gl);
 			clear_bit(GLF_DIRTY, &gl->gl_flags);
 		} else if (meta) {
 			gfs2_log_flush(gl->gl_sbd, gl);
-			gfs2_meta_sync(gl, flags | DIO_START | DIO_WAIT);
-		} else if (data)
-			gfs2_page_sync(gl, flags | DIO_START | DIO_WAIT);
+			gfs2_meta_sync(gl);
+		} else if (data) {
+			gfs2_page_writeback(gl);
+			gfs2_page_wait(gl);
+		}
 		if (flags & DIO_RELEASE)
 			gfs2_ail_empty_gl(gl);
 	}