[Devel] [PATCH 1/2] mm: move common segment checks to separate helper function (v6)

[Dmitriy Monakhov]

I realy don't want to be annoying by sending this patcheset over and over
again. If anyone think this patch is realy cappy, please comment what 
exectly is bad. Thank you.

Changes:
  - patch was split in two patches.
  - comments added. I think now it is clearly describe things.
  - make generic_segment_checks() inline
  - patch prepared against 2.6.20-mm3

How is tested:
 - LTP test, and other readv/writev op tests.

Signed-off-by: Monakhov Dmitriy <dmonakhov at openvz.org>
---
 mm/filemap.c |   76 +++++++++++++++++++++++++++++----------------------------
 1 files changed, 39 insertions(+), 37 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 8e1849a..0aadf5f 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1159,6 +1159,39 @@ success:
 	return size;
 }
 
+/*
+ * Performs necessary checks before doing a write
+ *
+ * Adjust number of segments and amount of bytes to write.
+ * Returns appropriate error code that caller should return or
+ * zero in case that write should be allowed.
+ */
+inline int generic_segment_checks(const struct iovec *iov,
+			unsigned long *nr_segs, size_t *count,
+			unsigned long access_flags)
+{
+	unsigned long   seg;
+	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.
+		 */
+		*count += iv->iov_len;
+		if (unlikely((ssize_t)(*count|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;
+		*count -= iv->iov_len;	/* This segment is no good */
+		break;
+	}
+	return 0;
+}
+
 /**
  * generic_file_aio_read - generic filesystem read routine
  * @iocb:	kernel I/O control block
@@ -1180,24 +1213,9 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
 	loff_t *ppos = &iocb->ki_pos;
 
 	count = 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.
-		 */
-		count += iv->iov_len;
-		if (unlikely((ssize_t)(count|iv->iov_len) < 0))
-			return -EINVAL;
-		if (access_ok(VERIFY_WRITE, iv->iov_base, iv->iov_len))
-			continue;
-		if (seg == 0)
-			return -EFAULT;
-		nr_segs = seg;
-		count -= iv->iov_len;	/* This segment is no good */
-		break;
-	}
+	retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
+	if (retval)
+		return retval;
 
 	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
 	if (filp->f_flags & O_DIRECT) {
@@ -2094,30 +2112,14 @@ __generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov,
 	size_t ocount;		/* original count */
 	size_t count;		/* after file limit checks */
 	struct inode 	*inode = mapping->host;
-	unsigned long	seg;
 	loff_t		pos;
 	ssize_t		written;
 	ssize_t		err;
 
 	ocount = 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.
-		 */
-		ocount += iv->iov_len;
-		if (unlikely((ssize_t)(ocount|iv->iov_len) < 0))
-			return -EINVAL;
-		if (access_ok(VERIFY_READ, iv->iov_base, iv->iov_len))
-			continue;
-		if (seg == 0)
-			return -EFAULT;
-		nr_segs = seg;
-		ocount -= iv->iov_len;	/* This segment is no good */
-		break;
-	}
+	err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
+	if (err)
+		return err;
 
 	count = ocount;
 	pos = *ppos;
-- 
1.5.0.1