[RFC PATCH 09/17] block: refactor iov_count_pages() from bio_{copy,map}_user_iov()

Dongsu Park
2014-12-22T11:50:14Z

From: Kent Overstreet <kmo@daterainc.com>

Refactor the common part in bio_copy_user_iov() and
__bio_map_user_iov() to separate out iov_count_pages() into the general
iov_iter API, instead of open coding iov iterations as done previously.

This commit should contain only literal replacements, without
functional changes.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
[dpark: add more description in commit message]
Signed-off-by: Dongsu Park <dongsu.park@profitbricks.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: "Hans J. Koch" <hjk@hansjkoch.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
---
block/bio.c | 43 ++++++-------------------------------------
include/linux/uio.h | 2 ++
lib/iovec.c | 30 ++++++++++++++++++++++++++++++
3 files changed, 38 insertions(+), 37 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 524b401..2adb68b 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1110,24 +1110,9 @@ struct bio *bio_copy_user_iov(struct request_queue *q,
unsigned int len;
unsigned int offset = map_data ? map_data->offset & ~PAGE_MASK : 0;

- for (i = 0; i < iter->nr_segs; i++) {
- unsigned long uaddr;
- unsigned long end;
- unsigned long start;
-
- uaddr = (unsigned long) iter->iov[i].iov_base;
- end = (uaddr + iter->iov[i].iov_len + PAGE_SIZE - 1)
- >> PAGE_SHIFT;
- start = uaddr >> PAGE_SHIFT;
-
- /*
- * Overflow, abort
- */
- if (end < start)
- return ERR_PTR(-EINVAL);
-
- nr_pages += end - start;
- }
+ nr_pages = iov_count_pages(iter, 0);
+ if (nr_pages < 0)
+ return ERR_PTR(nr_pages);

if (offset)
nr_pages++;
@@ -1257,25 +1242,9 @@ static struct bio *__bio_map_user_iov(struct request_queue *q,
struct iov_iter i;
struct iovec iov;

- iov_for_each(iov, i, *iter) {
- unsigned long uaddr = (unsigned long) iov.iov_base;
- unsigned long len = iov.iov_len;
- unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
- unsigned long start = uaddr >> PAGE_SHIFT;
-
- /*
- * Overflow, abort
- */
- if (end < start)
- return ERR_PTR(-EINVAL);
-
- nr_pages += end - start;
- /*
- * buffer must be aligned to at least hardsector size for now
- */
- if (uaddr & queue_dma_alignment(q))
- return ERR_PTR(-EINVAL);
- }
+ nr_pages = iov_count_pages(iter, queue_dma_alignment(q));
+ if (nr_pages < 0)
+ return ERR_PTR(nr_pages);

if (!nr_pages)
return ERR_PTR(-EINVAL);
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 1c5e453..142ff1b 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -72,6 +72,8 @@ static inline struct iovec iov_iter_iovec(const struct iov_iter *iter)

unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to);

+int iov_count_pages(const struct iov_iter *iter, unsigned align);
+
size_t iov_iter_copy_from_user_atomic(struct page *page,
struct iov_iter *i, unsigned long offset, size_t bytes);
void iov_iter_advance(struct iov_iter *i, size_t bytes);
diff --git a/lib/iovec.c b/lib/iovec.c
index 2d99cb4..2e75086 100644
--- a/lib/iovec.c
+++ b/lib/iovec.c
@@ -1,5 +1,7 @@
#include <linux/uaccess.h>
#include <linux/export.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
#include <linux/uio.h>

/*
@@ -85,3 +87,31 @@ int memcpy_fromiovecend(unsigned char *kdata, const struct iovec *iov,
return 0;
}
EXPORT_SYMBOL(memcpy_fromiovecend);
+
+int iov_count_pages(const struct iov_iter *iter, unsigned align)
+{
+ struct iov_iter i = *iter;
+ int nr_pages = 0;
+
+ while (iov_iter_count(&i)) {
+ unsigned long uaddr = (unsigned long) i.iov->iov_base +
+ i.iov_offset;
+ unsigned long len = i.iov->iov_len - i.iov_offset;
+
+ if ((uaddr & align) || (len & align))
+ return -EINVAL;
+
+ /*
+ * Overflow, abort
+ */
+ if (uaddr + len < uaddr)
+ return -EINVAL;
+
+ nr_pages += DIV_ROUND_UP(len + offset_in_page(uaddr),
+ PAGE_SIZE);
+ iov_iter_advance(&i, len);
+ }
+
+ return nr_pages;
+}
+EXPORT_SYMBOL(iov_count_pages);
--
2.1.0