[PATCH 1/7] block: simplify bio_map_kern

From: Christoph Hellwig
Date: Fri Jan 16 2015 - 07:05:59 EST


Just open code the trivial mapping from a kernel virtual address to
a bio instead of going through the complex user address mapping
machinery.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
block/bio.c | 60 ++++++++++++++++++++++++++++++++++++++++++++----------------
1 file changed, 44 insertions(+), 16 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 471d738..54da51e 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1563,9 +1563,8 @@ static void bio_copy_kern_endio(struct bio *bio, int err)
{
struct bio_vec *bvec;
const int read = bio_data_dir(bio) == READ;
- struct bio_map_data *bmd = bio->bi_private;
+ char *p = bio->bi_private;
int i;
- char *p = bmd->sgvecs[0].iov_base;

bio_for_each_segment_all(bvec, bio, i) {
char *addr = page_address(bvec->bv_page);
@@ -1577,7 +1576,6 @@ static void bio_copy_kern_endio(struct bio *bio, int err)
p += bvec->bv_len;
}

- kfree(bmd);
bio_put(bio);
}

@@ -1595,28 +1593,58 @@ static void bio_copy_kern_endio(struct bio *bio, int err)
struct bio *bio_copy_kern(struct request_queue *q, void *data, unsigned int len,
gfp_t gfp_mask, int reading)
{
- struct bio *bio;
+ unsigned long kaddr = (unsigned long)data;
+ unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+ unsigned long start = kaddr >> PAGE_SHIFT;
struct bio_vec *bvec;
- int i;
+ struct bio *bio;
+ void *p = data;
+ int nr_pages = 0, i;

- bio = bio_copy_user(q, NULL, (unsigned long)data, len, 1, gfp_mask);
- if (IS_ERR(bio))
- return bio;
+ /*
+ * Overflow, abort
+ */
+ if (end < start)
+ return ERR_PTR(-EINVAL);

- if (!reading) {
- void *p = data;
+ nr_pages = end - start;
+ bio = bio_kmalloc(gfp_mask, nr_pages);
+ if (!bio)
+ return ERR_PTR(-ENOMEM);

- bio_for_each_segment_all(bvec, bio, i) {
- char *addr = page_address(bvec->bv_page);
+ while (len) {
+ struct page *page;
+ unsigned int bytes = PAGE_SIZE;

- memcpy(addr, p, bvec->bv_len);
- p += bvec->bv_len;
- }
+ if (bytes > len)
+ bytes = len;
+
+ page = alloc_page(q->bounce_gfp | gfp_mask);
+ if (!page)
+ goto cleanup;
+
+ if (!reading)
+ memcpy(page_address(page), p, bytes);
+
+ if (bio_add_pc_page(q, bio, page, bytes, 0) < bytes)
+ break;
+
+ len -= bytes;
+ p += bytes;
}

- bio->bi_end_io = bio_copy_kern_endio;
+ if (!reading)
+ bio->bi_rw |= REQ_WRITE;

+ bio->bi_private = data;
+ bio->bi_end_io = bio_copy_kern_endio;
return bio;
+
+cleanup:
+ bio_for_each_segment_all(bvec, bio, i)
+ __free_page(bvec->bv_page);
+ bio_put(bio);
+ return ERR_PTR(-ENOMEM);
}
EXPORT_SYMBOL(bio_copy_kern);

--
1.9.1

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