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Commit 2c80929c authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Al Viro
Browse files

fuse: honour max_read and max_write in direct_io mode 



The third argument of fuse_get_user_pages() "nbytesp" refers to the number of
bytes a caller asked to pack into fuse request. This value may be lesser
than capacity of fuse request or iov_iter.  So fuse_get_user_pages() must
ensure that *nbytesp won't grow.

Now, when helper iov_iter_get_pages() performs all hard work of extracting
pages from iov_iter, it can be done by passing properly calculated
"maxsize" to the helper.

The other caller of iov_iter_get_pages() (dio_refill_pages()) doesn't need
this capability, so pass LONG_MAX as the maxsize argument here.

Fixes: c9c37e2e ("fuse: switch to iov_iter_get_pages()")
Reported-by: default avatarWerner Baumann <werner.baumann@onlinehome.de>
Tested-by: default avatarMaxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent b928095b

fs/direct-io.c

+1 −1
Original line number Diff line number Diff line
@@ -158,7 +158,7 @@ static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio) 
{

	ssize_t ret;



	ret = iov_iter_get_pages(sdio->iter, dio->pages, DIO_PAGES,

	ret = iov_iter_get_pages(sdio->iter, dio->pages, LONG_MAX, DIO_PAGES,

				&sdio->from);



	if (ret < 0 && sdio->blocks_available && (dio->rw & WRITE)) {

fs/fuse/file.c

+1 −0
Original line number Diff line number Diff line
@@ -1305,6 +1305,7 @@ static int fuse_get_user_pages(struct fuse_req *req, struct iov_iter *ii, 
		size_t start;

		ssize_t ret = iov_iter_get_pages(ii,

					&req->pages[req->num_pages],

					*nbytesp - nbytes,

					req->max_pages - req->num_pages,

					&start);

		if (ret < 0)

include/linux/uio.h

+1 −1
Original line number Diff line number Diff line
@@ -84,7 +84,7 @@ unsigned long iov_iter_alignment(const struct iov_iter *i); 
void iov_iter_init(struct iov_iter *i, int direction, const struct iovec *iov,

			unsigned long nr_segs, size_t count);

ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages,

			unsigned maxpages, size_t *start);

			size_t maxsize, unsigned maxpages, size_t *start);

ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages,

			size_t maxsize, size_t *start);

int iov_iter_npages(const struct iov_iter *i, int maxpages);

mm/iov_iter.c

+9 −5
Original line number Diff line number Diff line
@@ -310,7 +310,7 @@ void iov_iter_init(struct iov_iter *i, int direction, 
EXPORT_SYMBOL(iov_iter_init);



static ssize_t get_pages_iovec(struct iov_iter *i,

		   struct page **pages, unsigned maxpages,

		   struct page **pages, size_t maxsize, unsigned maxpages,

		   size_t *start)

{

	size_t offset = i->iov_offset;
@@ -323,6 +323,8 @@ static ssize_t get_pages_iovec(struct iov_iter *i, 
	len = iov->iov_len - offset;

	if (len > i->count)

		len = i->count;

	if (len > maxsize)

		len = maxsize;

	addr = (unsigned long)iov->iov_base + offset;

	len += *start = addr & (PAGE_SIZE - 1);

	if (len > maxpages * PAGE_SIZE)
@@ -588,13 +590,15 @@ static unsigned long alignment_bvec(const struct iov_iter *i) 
}



static ssize_t get_pages_bvec(struct iov_iter *i,

		   struct page **pages, unsigned maxpages,

		   struct page **pages, size_t maxsize, unsigned maxpages,

		   size_t *start)

{

	const struct bio_vec *bvec = i->bvec;

	size_t len = bvec->bv_len - i->iov_offset;

	if (len > i->count)

		len = i->count;

	if (len > maxsize)

		len = maxsize;

	/* can't be more than PAGE_SIZE */

	*start = bvec->bv_offset + i->iov_offset;
@@ -711,13 +715,13 @@ unsigned long iov_iter_alignment(const struct iov_iter *i) 
EXPORT_SYMBOL(iov_iter_alignment);



ssize_t iov_iter_get_pages(struct iov_iter *i,

		   struct page **pages, unsigned maxpages,

		   struct page **pages, size_t maxsize, unsigned maxpages,

		   size_t *start)

{

	if (i->type & ITER_BVEC)

		return get_pages_bvec(i, pages, maxpages, start);

		return get_pages_bvec(i, pages, maxsize, maxpages, start);

	else

		return get_pages_iovec(i, pages, maxpages, start);

		return get_pages_iovec(i, pages, maxsize, maxpages, start);

}

EXPORT_SYMBOL(iov_iter_get_pages);