From: Eric Sandeen <sandeen@redhat.com>
Date: Tue, 8 Jul 2008 15:32:19 -0500
Subject: [fs] add buffer_submit_read and bh_uptodate_or_lock
Message-id: 4873CED3.4050902@redhat.com
O-Subject: [PATCH RHEL5 8/9] buffer_submit_read and bh_uptodate_or_lock
Bugzilla: 443896
RH-Acked-by: Jeff Moyer <jmoyer@redhat.com>
RH-Acked-by: Jeff Layton <jlayton@redhat.com>
RH-Acked-by: Alexander Viro <aviro@redhat.com>

This is for:

Bugzilla Bug 443896: RFE: [Ext4 enabler] backport vfs
helpers to facilitate ext4 backport and testing

From: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Date: Tue, 29 Jan 2008 04:58:26 +0000 (-0500)
Subject: Add buffer head related helper functions
X-Git-Tag: v2.6.25-rc1~11662~27
X-Git-Url: http://git.engineering.redhat.com/?p=linux-2.6.git;a=commitdiff_plain;h=389d1b083c767a360ec84b27a95da06244becec8

Add buffer head related helper functions

Add buffer head related helper function bh_uptodate_or_lock and
bh_submit_read which can be used by file system

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

diff --git a/fs/buffer.c b/fs/buffer.c
index a70fa87..17ebeab 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3175,6 +3175,50 @@ static int buffer_cpu_notify(struct notifier_block *self,
 }
 #endif /* CONFIG_HOTPLUG_CPU */
 
+/**
+ * bh_uptodate_or_lock - Test whether the buffer is uptodate
+ * @bh: struct buffer_head
+ *
+ * Return true if the buffer is up-to-date and false,
+ * with the buffer locked, if not.
+ */
+int bh_uptodate_or_lock(struct buffer_head *bh)
+{
+	if (!buffer_uptodate(bh)) {
+		lock_buffer(bh);
+		if (!buffer_uptodate(bh))
+			return 0;
+		unlock_buffer(bh);
+	}
+	return 1;
+}
+EXPORT_SYMBOL(bh_uptodate_or_lock);
+
+/**
+ * bh_submit_read - Submit a locked buffer for reading
+ * @bh: struct buffer_head
+ *
+ * Returns zero on success and -EIO on error.
+ */
+int bh_submit_read(struct buffer_head *bh)
+{
+	BUG_ON(!buffer_locked(bh));
+
+	if (buffer_uptodate(bh)) {
+		unlock_buffer(bh);
+		return 0;
+	}
+
+	get_bh(bh);
+	bh->b_end_io = end_buffer_read_sync;
+	submit_bh(READ, bh);
+	wait_on_buffer(bh);
+	if (buffer_uptodate(bh))
+		return 0;
+	return -EIO;
+}
+EXPORT_SYMBOL(bh_submit_read);
+
 void __init buffer_init(void)
 {
 	int nrpages;
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index bc916a0..41c7fed 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -184,6 +184,8 @@ int sync_dirty_buffer(struct buffer_head *bh);
 int submit_bh(int, struct buffer_head *);
 void write_boundary_block(struct block_device *bdev,
 			sector_t bblock, unsigned blocksize);
+int bh_uptodate_or_lock(struct buffer_head *bh);
+int bh_submit_read(struct buffer_head *bh);
 
 extern int buffer_heads_over_limit;