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Message-ID: <20230630152524.661208-10-dhowells@redhat.com>
Date: Fri, 30 Jun 2023 16:25:22 +0100
From: David Howells <dhowells@...hat.com>
To: Jens Axboe <axboe@...nel.dk>, Al Viro <viro@...iv.linux.org.uk>,
Christoph Hellwig <hch@...radead.org>
Cc: David Howells <dhowells@...hat.com>,
Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>,
Jeff Layton <jlayton@...nel.org>,
David Hildenbrand <david@...hat.com>,
Jason Gunthorpe <jgg@...dia.com>,
Logan Gunthorpe <logang@...tatee.com>,
Hillf Danton <hdanton@...a.com>,
Christian Brauner <brauner@...nel.org>,
linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Christoph Hellwig <hch@....de>,
Christian Brauner <christian@...uner.io>,
Herbert Xu <herbert@...dor.apana.org.au>,
linux-crypto@...r.kernel.org
Subject: [RFC PATCH 09/11] iov_iter: Use I/O dir flags with iov_iter_extract_pages()
Define flags to pass into iov_iter_extract_pages() to indicate I/O
direction. A warning is issued and the function fails if neither or both
flags are set. The flag is also checked against the iterator's data_source
flag.
Also make extract_iter_to_sg() check the flags and propagate them to
iov_iter_extract_pages().
Finally, make the callers pass the flags into iov_iter_extract_pages() and
extract_iter_to_sg().
Signed-off-by: David Howells <dhowells@...hat.com>
cc: Christoph Hellwig <hch@....de>
cc: Jens Axboe <axboe@...nel.dk>
cc: Christian Brauner <christian@...uner.io>
cc: Alexander Viro <viro@...iv.linux.org.uk>
cc: Herbert Xu <herbert@...dor.apana.org.au>
cc: linux-block@...r.kernel.org
cc: linux-fsdevel@...r.kernel.org
cc: linux-crypto@...r.kernel.org
---
block/bio.c | 6 ++++++
block/blk-map.c | 3 +++
crypto/af_alg.c | 5 +++--
crypto/algif_hash.c | 3 ++-
fs/direct-io.c | 6 +++++-
include/linux/bio.h | 18 ++++++++++++++++--
include/linux/uio.h | 5 ++++-
lib/iov_iter.c | 12 ++++++++++--
lib/scatterlist.c | 12 ++++++++++--
9 files changed, 59 insertions(+), 11 deletions(-)
diff --git a/block/bio.c b/block/bio.c
index 8672179213b9..440d4889ba13 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1242,6 +1242,8 @@ static int bio_iov_add_zone_append_page(struct bio *bio, struct page *page,
* will have to be cleaned up in the way indicated by the BIO_PAGE_PINNED flag.
* For a multi-segment *iter, this function only adds pages from the next
* non-empty segment of the iov iterator.
+ *
+ * The I/O direction is determined from the bio operation type.
*/
static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
{
@@ -1263,6 +1265,8 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
BUILD_BUG_ON(PAGE_PTRS_PER_BVEC < 2);
pages += entries_left * (PAGE_PTRS_PER_BVEC - 1);
+ extraction_flags |= bio_is_write(bio) ? WRITE_FROM_ITER : READ_INTO_ITER;
+
if (bio->bi_bdev && blk_queue_pci_p2pdma(bio->bi_bdev->bd_disk->queue))
extraction_flags |= ITER_ALLOW_P2PDMA;
@@ -1332,6 +1336,8 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
* fit into the bio, or are requested in @iter, whatever is smaller. If
* MM encounters an error pinning the requested pages, it stops. Error
* is returned only if 0 pages could be pinned.
+ *
+ * The bio operation indicates the data direction.
*/
int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
{
diff --git a/block/blk-map.c b/block/blk-map.c
index f8fe114ae433..71de2cf9bf4e 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -279,6 +279,9 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
if (bio == NULL)
return -ENOMEM;
+ extraction_flags |=
+ bio_is_write(bio) ? WRITE_FROM_ITER : READ_INTO_ITER;
+
if (blk_queue_pci_p2pdma(rq->q))
extraction_flags |= ITER_ALLOW_P2PDMA;
if (iov_iter_extract_will_pin(iter))
diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index 6218c773d71c..c62ac5e32aeb 100644
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -1042,7 +1042,8 @@ int af_alg_sendmsg(struct socket *sock, struct msghdr *msg, size_t size,
};
plen = extract_iter_to_sg(&msg->msg_iter, len, &sgtable,
- MAX_SGL_ENTS - sgl->cur, 0);
+ MAX_SGL_ENTS - sgl->cur,
+ WRITE_FROM_ITER);
if (plen < 0) {
err = plen;
goto unlock;
@@ -1247,7 +1248,7 @@ int af_alg_get_rsgl(struct sock *sk, struct msghdr *msg, int flags,
sg_init_table(rsgl->sgl.sgt.sgl, ALG_MAX_PAGES);
err = extract_iter_to_sg(&msg->msg_iter, seglen, &rsgl->sgl.sgt,
- ALG_MAX_PAGES, 0);
+ ALG_MAX_PAGES, READ_INTO_ITER);
if (err < 0) {
rsgl->sg_num_bytes = 0;
return err;
diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c
index 0ab43e149f0e..b343c4973dbf 100644
--- a/crypto/algif_hash.c
+++ b/crypto/algif_hash.c
@@ -115,7 +115,8 @@ static int hash_sendmsg(struct socket *sock, struct msghdr *msg,
ctx->sgl.need_unpin = iov_iter_extract_will_pin(&msg->msg_iter);
err = extract_iter_to_sg(&msg->msg_iter, LONG_MAX,
- &ctx->sgl.sgt, npages, 0);
+ &ctx->sgl.sgt, npages,
+ WRITE_FROM_ITER);
if (err < 0)
goto unlock_free;
len = err;
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 2b517cc5b32d..3316d2f8f21c 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -168,10 +168,14 @@ static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)
{
struct page **pages = dio->pages;
const enum req_op dio_op = dio->opf & REQ_OP_MASK;
+ unsigned int extraction_flags;
ssize_t ret;
+ extraction_flags =
+ op_is_write(dio_op) ? WRITE_FROM_ITER : READ_INTO_ITER;
+
ret = iov_iter_extract_pages(sdio->iter, &pages, LONG_MAX,
- DIO_PAGES, 0, &sdio->from);
+ DIO_PAGES, extraction_flags, &sdio->from);
if (ret < 0 && sdio->blocks_available && dio_op == REQ_OP_WRITE) {
/*
diff --git a/include/linux/bio.h b/include/linux/bio.h
index c4f5b5228105..d4b4c477e69b 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -42,11 +42,25 @@ static inline unsigned int bio_max_segs(unsigned int nr_segs)
#define bio_sectors(bio) bvec_iter_sectors((bio)->bi_iter)
#define bio_end_sector(bio) bvec_iter_end_sector((bio)->bi_iter)
+/**
+ * bio_is_write - Query if the I/O direction is towards the disk
+ * @bio: The bio to query
+ *
+ * Return true if this is some sort of write operation - ie. the data is going
+ * towards the disk.
+ */
+static inline bool bio_is_write(const struct bio *bio)
+{
+ return op_is_write(bio_op(bio));
+}
+
/*
* Return the data direction, READ or WRITE.
*/
-#define bio_data_dir(bio) \
- (op_is_write(bio_op(bio)) ? WRITE : READ)
+static inline int bio_data_dir(const struct bio *bio)
+{
+ return bio_is_write(bio) ? WRITE : READ;
+}
/*
* Check whether this bio carries any data or not. A NULL bio is allowed.
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 70e12f536f8f..6ea7c1b589c1 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -379,8 +379,11 @@ static inline void iov_iter_ubuf(struct iov_iter *i, unsigned int direction,
};
}
/* Flags for iov_iter_get/extract_pages*() */
+/* Indicate if we are going to be writing from the buffer or reading into it. */
+#define WRITE_FROM_ITER ((__force iov_iter_extraction_t)0x01) // == WRITE
+#define READ_INTO_ITER ((__force iov_iter_extraction_t)0x02)
/* Allow P2PDMA on the extracted pages */
-#define ITER_ALLOW_P2PDMA ((__force iov_iter_extraction_t)0x01)
+#define ITER_ALLOW_P2PDMA ((__force iov_iter_extraction_t)0x04)
ssize_t iov_iter_extract_pages(struct iov_iter *i, struct page ***pages,
size_t maxsize, unsigned int maxpages,
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index b8c52231a6ff..d31f40b69da5 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1791,8 +1791,10 @@ static ssize_t iov_iter_extract_user_pages(struct iov_iter *i,
* that the caller allocated a page list at least @maxpages in size and this
* will be filled in.
*
- * @extraction_flags can have ITER_ALLOW_P2PDMA set to request peer-to-peer DMA
- * be allowed on the pages extracted.
+ * @extraction_flags should have either WRITE_FROM_ITER or READ_INTO_ITER to
+ * indicate the direction the data is intended to flow to/from the buffer and
+ * can have ITER_ALLOW_P2PDMA set to request peer-to-peer DMA be allowed on the
+ * pages extracted.
*
* The iov_iter_extract_will_pin() function can be used to query how cleanup
* should be performed.
@@ -1823,6 +1825,12 @@ ssize_t iov_iter_extract_pages(struct iov_iter *i,
iov_iter_extraction_t extraction_flags,
size_t *offset0)
{
+ unsigned int dir = extraction_flags & (READ_INTO_ITER | WRITE_FROM_ITER);
+
+ if (WARN_ON_ONCE(dir != READ_INTO_ITER && dir != WRITE_FROM_ITER) ||
+ WARN_ON_ONCE((dir & WRITE) != i->data_source))
+ return -EFAULT;
+
maxsize = min_t(size_t, min_t(size_t, maxsize, i->count), MAX_RW_COUNT);
if (!maxsize)
return 0;
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index e97d7060329e..116ce320eb36 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -1326,8 +1326,10 @@ static ssize_t extract_xarray_to_sg(struct iov_iter *iter,
*
* No end mark is placed on the scatterlist; that's left to the caller.
*
- * @extraction_flags can have ITER_ALLOW_P2PDMA set to request peer-to-peer DMA
- * be allowed on the pages extracted.
+ * @extraction_flags should have either WRITE_FROM_ITER or READ_INTO_ITER to
+ * indicate the direction the data is intended to flow to/from the buffer and
+ * can have ITER_ALLOW_P2PDMA set to request peer-to-peer DMA be allowed on the
+ * pages extracted.
*
* If successful, @sgtable->nents is updated to include the number of elements
* added and the number of bytes added is returned. @sgtable->orig_nents is
@@ -1340,6 +1342,12 @@ ssize_t extract_iter_to_sg(struct iov_iter *iter, size_t maxsize,
struct sg_table *sgtable, unsigned int sg_max,
iov_iter_extraction_t extraction_flags)
{
+ unsigned int dir = extraction_flags & (READ_INTO_ITER | WRITE_FROM_ITER);
+
+ if (WARN_ON_ONCE(dir != READ_INTO_ITER && dir != WRITE_FROM_ITER) ||
+ WARN_ON_ONCE((dir & WRITE) != iter->data_source))
+ return -EFAULT;
+
if (maxsize == 0)
return 0;
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