From: Eric Sandeen <sandeen@redhat.com>
Date: Wed, 25 Mar 2009 15:41:51 -0500
Subject: [mm] generic_segment_checks helper
Message-id: 49CA970F.9010007@redhat.com
O-Subject: [PATCH 1/10] generic_segment_checks helper
Bugzilla: 470845
RH-Acked-by: Steven Whitehouse <swhiteho@redhat.com>
RH-Acked-by: Josef Bacik <josef@redhat.com>

Partial backport of:

commit 0ceb331433e8aad9c5f441a965d7c681f8b9046f
Author: Dmitriy Monakhov <dmonakhov@openvz.org>
Date:   Tue May 8 00:23:02 2007 -0700

    mm: move common segment checks to separate helper function

    [akpm@linux-foundation.org: cleanup]
    Signed-off-by: Monakhov Dmitriy <dmonakhov@openvz.org>
    Cc: Christoph Hellwig <hch@lst.de>
    Acked-by: Anton Altaparmakov <aia21@cam.ac.uk>
    Acked-by: David Chinner <dgc@sgi.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Also remove gfs2's private copy of this.

diff --git a/fs/gfs2/ops_file.c b/fs/gfs2/ops_file.c
index 965aa19..867f2c9 100644
--- a/fs/gfs2/ops_file.c
+++ b/fs/gfs2/ops_file.c
@@ -955,44 +955,6 @@ gfs2_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
 	return written ? written : status;
 }
 
-/*
- * Performs necessary checks before doing a write
- * @iov:	io vector request
- * @nr_segs:	number of segments in the iovec
- * @count:	number of bytes to write
- * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
- *
- * Adjust number of segments and amount of bytes to write (nr_segs should be
- * properly initialized first). Returns appropriate error code that caller
- * should return or zero in case that write should be allowed.
- */
-static int generic_segment_checks(const struct iovec *iov,
-			unsigned long *nr_segs, size_t *count, int access_flags)
-{
-	unsigned long   seg;
-	size_t cnt = 0;
-	for (seg = 0; seg < *nr_segs; seg++) {
-		const struct iovec *iv = &iov[seg];
-
-		/*
-		 * If any segment has a negative length, or the cumulative
-		 * length ever wraps negative then return -EINVAL.
-		 */
-		cnt += iv->iov_len;
-		if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
-			return -EINVAL;
-		if (access_ok(access_flags, iv->iov_base, iv->iov_len))
-			continue;
-		if (seg == 0)
-			return -EFAULT;
-		*nr_segs = seg;
-		cnt -= iv->iov_len;	/* This segment is no good */
-		break;
-	}
-	*count = cnt;
-	return 0;
-}
-
 static ssize_t
 __gfs2_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov,
 			     unsigned long nr_segs, loff_t *ppos)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 2c336cf..5f30889 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1859,6 +1859,8 @@ extern int generic_file_buffered_write_one_kernel_page(struct address_space *,
 						       pgoff_t, struct page *);
 extern ssize_t do_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos);
 extern ssize_t do_sync_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos);
+extern int generic_segment_checks(const struct iovec *iov,
+		unsigned long *nr_segs, size_t *count, int access_flags);
 ssize_t generic_file_write_nolock(struct file *file, const struct iovec *iov,
 				unsigned long nr_segs, loff_t *ppos);
 extern ssize_t generic_file_sendfile(struct file *, loff_t *, size_t, read_actor_t, void *);
diff --git a/mm/filemap.c b/mm/filemap.c
index 3c578e2..ecb40af 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1135,6 +1135,45 @@ success:
 	return size;
 }
 
+/*
+ * Performs necessary checks before doing a write
+ * @iov:	io vector request
+ * @nr_segs:	number of segments in the iovec
+ * @count:	number of bytes to write
+ * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
+ *
+ * Adjust number of segments and amount of bytes to write (nr_segs should be
+ * properly initialized first). Returns appropriate error code that caller
+ * should return or zero in case that write should be allowed.
+ */
+int generic_segment_checks(const struct iovec *iov,
+			unsigned long *nr_segs, size_t *count, int access_flags)
+{
+	unsigned long   seg;
+	size_t cnt = 0;
+	for (seg = 0; seg < *nr_segs; seg++) {
+		const struct iovec *iv = &iov[seg];
+
+		/*
+		 * If any segment has a negative length, or the cumulative
+		 * length ever wraps negative then return -EINVAL.
+		 */
+		cnt += iv->iov_len;
+		if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
+			return -EINVAL;
+		if (access_ok(access_flags, iv->iov_base, iv->iov_len))
+			continue;
+		if (seg == 0)
+			return -EFAULT;
+		*nr_segs = seg;
+		cnt -= iv->iov_len;	/* This segment is no good */
+		break;
+	}
+	*count = cnt;
+	return 0;
+}
+EXPORT_SYMBOL(generic_segment_checks);
+
 /**
  * __generic_file_aio_read - generic filesystem read routine
  * @iocb:	kernel I/O control block