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Commit 62a8067a authored by Al Viro's avatar Al Viro
Browse files

bio_vec-backed iov_iter 



New variant of iov_iter - ITER_BVEC in iter->type, backed with
bio_vec array instead of iovec one.  Primitives taught to deal
with such beasts, __swap_write() switched to using that kind
of iov_iter.

Note that bio_vec is just a <page, offset, length> triple - there's
nothing block-specific about it.  I've left the definition where it
was, but took it from under ifdef CONFIG_BLOCK.

Next target: ->splice_write()...

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 81055e58

fs/fuse/file.c

+1 −1
Original line number Diff line number Diff line
@@ -1288,7 +1288,7 @@ static int fuse_get_user_pages(struct fuse_req *req, struct iov_iter *ii, 
	size_t nbytes = 0;  /* # bytes already packed in req */



	/* Special case for kernel I/O: can copy directly into the buffer */

	if (ii->type & REQ_KERNEL) {

	if (ii->type & ITER_KVEC) {

		unsigned long user_addr = fuse_get_user_addr(ii);

		size_t frag_size = fuse_get_frag_size(ii, *nbytesp);

include/linux/blk_types.h

+2 −2
Original line number Diff line number Diff line
@@ -5,8 +5,6 @@ 
#ifndef __LINUX_BLK_TYPES_H

#define __LINUX_BLK_TYPES_H



#ifdef CONFIG_BLOCK



#include <linux/types.h>



struct bio_set;
@@ -28,6 +26,8 @@ struct bio_vec { 
	unsigned int	bv_offset;

};



#ifdef CONFIG_BLOCK



struct bvec_iter {

	sector_t		bi_sector;	/* device address in 512 byte

						   sectors */

include/linux/uio.h

+12 −2
Original line number Diff line number Diff line
@@ -19,12 +19,21 @@ struct kvec { 
	size_t iov_len;

};



enum {

	ITER_IOVEC = 0,

	ITER_KVEC = 2,

	ITER_BVEC = 4,

};



struct iov_iter {

	int type;

	const struct iovec *iov;

	unsigned long nr_segs;

	size_t iov_offset;

	size_t count;

	union {

		const struct iovec *iov;

		const struct bio_vec *bvec;

	};

	unsigned long nr_segs;

};



/*
@@ -54,6 +63,7 @@ static inline struct iovec iov_iter_iovec(const struct iov_iter *iter) 
}



#define iov_for_each(iov, iter, start)				\

	if (!((start).type & ITER_BVEC))			\

	for (iter = (start);					\

	     (iter).count &&					\

	     ((iov = iov_iter_iovec(&(iter))), 1);		\

mm/iov_iter.c

+358 −32
Original line number Diff line number Diff line
@@ -4,7 +4,7 @@ 
#include <linux/slab.h>

#include <linux/vmalloc.h>



size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,

static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t bytes,

			 struct iov_iter *i)

{

	size_t skip, copy, left, wanted;
@@ -84,9 +84,8 @@ size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes, 
	i->iov_offset = skip;

	return wanted - bytes;

}

EXPORT_SYMBOL(copy_page_to_iter);



size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,

static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t bytes,

			 struct iov_iter *i)

{

	size_t skip, copy, left, wanted;
@@ -166,7 +165,6 @@ size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes, 
	i->iov_offset = skip;

	return wanted - bytes;

}

EXPORT_SYMBOL(copy_page_from_iter);



static size_t __iovec_copy_from_user_inatomic(char *vaddr,

			const struct iovec *iov, size_t base, size_t bytes)
@@ -195,7 +193,7 @@ static size_t __iovec_copy_from_user_inatomic(char *vaddr, 
 * were successfully copied.  If a fault is encountered then return the number of

 * bytes which were copied.

 */

size_t iov_iter_copy_from_user_atomic(struct page *page,

static size_t copy_from_user_atomic_iovec(struct page *page,

		struct iov_iter *i, unsigned long offset, size_t bytes)

{

	char *kaddr;
@@ -215,9 +213,8 @@ size_t iov_iter_copy_from_user_atomic(struct page *page, 


	return copied;

}

EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);



void iov_iter_advance(struct iov_iter *i, size_t bytes)

static void advance_iovec(struct iov_iter *i, size_t bytes)

{

	BUG_ON(i->count < bytes);
@@ -252,7 +249,6 @@ void iov_iter_advance(struct iov_iter *i, size_t bytes) 
		i->nr_segs = nr_segs;

	}

}

EXPORT_SYMBOL(iov_iter_advance);



/*

 * Fault in the first iovec of the given iov_iter, to a maximum length
@@ -265,26 +261,16 @@ EXPORT_SYMBOL(iov_iter_advance); 
 */

int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)

{

	if (!(i->type & ITER_BVEC)) {

		char __user *buf = i->iov->iov_base + i->iov_offset;

		bytes = min(bytes, i->iov->iov_len - i->iov_offset);

		return fault_in_pages_readable(buf, bytes);

	}

EXPORT_SYMBOL(iov_iter_fault_in_readable);



/*

 * Return the count of just the current iov_iter segment.

 */

size_t iov_iter_single_seg_count(const struct iov_iter *i)

{

	const struct iovec *iov = i->iov;

	if (i->nr_segs == 1)

		return i->count;

	else

		return min(i->count, iov->iov_len - i->iov_offset);

	return 0;

}

EXPORT_SYMBOL(iov_iter_single_seg_count);

EXPORT_SYMBOL(iov_iter_fault_in_readable);



unsigned long iov_iter_alignment(const struct iov_iter *i)

static unsigned long alignment_iovec(const struct iov_iter *i)

{

	const struct iovec *iov = i->iov;

	unsigned long res;
@@ -307,7 +293,6 @@ unsigned long iov_iter_alignment(const struct iov_iter *i) 
	res |= (unsigned long)iov->iov_base | size;

	return res;

}

EXPORT_SYMBOL(iov_iter_alignment);



void iov_iter_init(struct iov_iter *i, int direction,

			const struct iovec *iov, unsigned long nr_segs,
@@ -315,7 +300,7 @@ void iov_iter_init(struct iov_iter *i, int direction, 
{

	/* It will get better.  Eventually... */

	if (segment_eq(get_fs(), KERNEL_DS))

		direction |= REQ_KERNEL;

		direction |= ITER_KVEC;

	i->type = direction;

	i->iov = iov;

	i->nr_segs = nr_segs;
@@ -324,7 +309,7 @@ void iov_iter_init(struct iov_iter *i, int direction, 
}

EXPORT_SYMBOL(iov_iter_init);



ssize_t iov_iter_get_pages(struct iov_iter *i,

static ssize_t get_pages_iovec(struct iov_iter *i,

		   struct page **pages, size_t maxsize,

		   size_t *start)

{
@@ -349,9 +334,8 @@ ssize_t iov_iter_get_pages(struct iov_iter *i, 
		return res;

	return (res == n ? len : res * PAGE_SIZE) - *start;

}

EXPORT_SYMBOL(iov_iter_get_pages);



ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,

static ssize_t get_pages_alloc_iovec(struct iov_iter *i,

		   struct page ***pages, size_t maxsize,

		   size_t *start)

{
@@ -387,9 +371,8 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, 
	*pages = p;

	return (res == n ? len : res * PAGE_SIZE) - *start;

}

EXPORT_SYMBOL(iov_iter_get_pages_alloc);



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

static int iov_iter_npages_iovec(const struct iov_iter *i, int maxpages)

{

	size_t offset = i->iov_offset;

	size_t size = i->count;
@@ -414,4 +397,347 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages) 
	}

	return min(npages, maxpages);

}



static void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len)

{

	char *from = kmap_atomic(page);

	memcpy(to, from + offset, len);

	kunmap_atomic(from);

}



static void memcpy_to_page(struct page *page, size_t offset, char *from, size_t len)

{

	char *to = kmap_atomic(page);

	memcpy(to + offset, from, len);

	kunmap_atomic(to);

}



static size_t copy_page_to_iter_bvec(struct page *page, size_t offset, size_t bytes,

			 struct iov_iter *i)

{

	size_t skip, copy, wanted;

	const struct bio_vec *bvec;

	void *kaddr, *from;



	if (unlikely(bytes > i->count))

		bytes = i->count;



	if (unlikely(!bytes))

		return 0;



	wanted = bytes;

	bvec = i->bvec;

	skip = i->iov_offset;

	copy = min_t(size_t, bytes, bvec->bv_len - skip);



	kaddr = kmap_atomic(page);

	from = kaddr + offset;

	memcpy_to_page(bvec->bv_page, skip + bvec->bv_offset, from, copy);

	skip += copy;

	from += copy;

	bytes -= copy;

	while (bytes) {

		bvec++;

		copy = min(bytes, (size_t)bvec->bv_len);

		memcpy_to_page(bvec->bv_page, bvec->bv_offset, from, copy);

		skip = copy;

		from += copy;

		bytes -= copy;

	}

	kunmap_atomic(kaddr);

	if (skip == bvec->bv_len) {

		bvec++;

		skip = 0;

	}

	i->count -= wanted - bytes;

	i->nr_segs -= bvec - i->bvec;

	i->bvec = bvec;

	i->iov_offset = skip;

	return wanted - bytes;

}



static size_t copy_page_from_iter_bvec(struct page *page, size_t offset, size_t bytes,

			 struct iov_iter *i)

{

	size_t skip, copy, wanted;

	const struct bio_vec *bvec;

	void *kaddr, *to;



	if (unlikely(bytes > i->count))

		bytes = i->count;



	if (unlikely(!bytes))

		return 0;



	wanted = bytes;

	bvec = i->bvec;

	skip = i->iov_offset;



	kaddr = kmap_atomic(page);



	to = kaddr + offset;



	copy = min(bytes, bvec->bv_len - skip);



	memcpy_from_page(to, bvec->bv_page, bvec->bv_offset + skip, copy);



	to += copy;

	skip += copy;

	bytes -= copy;



	while (bytes) {

		bvec++;

		copy = min(bytes, (size_t)bvec->bv_len);

		memcpy_from_page(to, bvec->bv_page, bvec->bv_offset, copy);

		skip = copy;

		to += copy;

		bytes -= copy;

	}

	kunmap_atomic(kaddr);

	if (skip == bvec->bv_len) {

		bvec++;

		skip = 0;

	}

	i->count -= wanted;

	i->nr_segs -= bvec - i->bvec;

	i->bvec = bvec;

	i->iov_offset = skip;

	return wanted;

}



static size_t copy_from_user_bvec(struct page *page,

		struct iov_iter *i, unsigned long offset, size_t bytes)

{

	char *kaddr;

	size_t left;

	const struct bio_vec *bvec;

	size_t base = i->iov_offset;



	kaddr = kmap_atomic(page);

	for (left = bytes, bvec = i->bvec; left; bvec++, base = 0) {

		size_t copy = min(left, bvec->bv_len - base);

		if (!bvec->bv_len)

			continue;

		memcpy_from_page(kaddr + offset, bvec->bv_page,

				 bvec->bv_offset + base, copy);

		offset += copy;

		left -= copy;

	}

	kunmap_atomic(kaddr);

	return bytes;

}



static void advance_bvec(struct iov_iter *i, size_t bytes)

{

	BUG_ON(i->count < bytes);



	if (likely(i->nr_segs == 1)) {

		i->iov_offset += bytes;

		i->count -= bytes;

	} else {

		const struct bio_vec *bvec = i->bvec;

		size_t base = i->iov_offset;

		unsigned long nr_segs = i->nr_segs;



		/*

		 * The !iov->iov_len check ensures we skip over unlikely

		 * zero-length segments (without overruning the iovec).

		 */

		while (bytes || unlikely(i->count && !bvec->bv_len)) {

			int copy;



			copy = min(bytes, bvec->bv_len - base);

			BUG_ON(!i->count || i->count < copy);

			i->count -= copy;

			bytes -= copy;

			base += copy;

			if (bvec->bv_len == base) {

				bvec++;

				nr_segs--;

				base = 0;

			}

		}

		i->bvec = bvec;

		i->iov_offset = base;

		i->nr_segs = nr_segs;

	}

}



static unsigned long alignment_bvec(const struct iov_iter *i)

{

	const struct bio_vec *bvec = i->bvec;

	unsigned long res;

	size_t size = i->count;

	size_t n;



	if (!size)

		return 0;



	res = bvec->bv_offset + i->iov_offset;

	n = bvec->bv_len - i->iov_offset;

	if (n >= size)

		return res | size;

	size -= n;

	res |= n;

	while (size > (++bvec)->bv_len) {

		res |= bvec->bv_offset | bvec->bv_len;

		size -= bvec->bv_len;

	}

	res |= bvec->bv_offset | size;

	return res;

}



static ssize_t get_pages_bvec(struct iov_iter *i,

		   struct page **pages, size_t maxsize,

		   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;

	*start = bvec->bv_offset + i->iov_offset;



	get_page(*pages = bvec->bv_page);



	return len;

}



static ssize_t get_pages_alloc_bvec(struct iov_iter *i,

		   struct page ***pages, size_t maxsize,

		   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;

	*start = bvec->bv_offset + i->iov_offset;



	*pages = kmalloc(sizeof(struct page *), GFP_KERNEL);

	if (!*pages)

		return -ENOMEM;



	get_page(**pages = bvec->bv_page);



	return len;

}



static int iov_iter_npages_bvec(const struct iov_iter *i, int maxpages)

{

	size_t offset = i->iov_offset;

	size_t size = i->count;

	const struct bio_vec *bvec = i->bvec;

	int npages = 0;

	int n;



	for (n = 0; size && n < i->nr_segs; n++, bvec++) {

		size_t len = bvec->bv_len - offset;

		offset = 0;

		if (unlikely(!len))	/* empty segment */

			continue;

		if (len > size)

			len = size;

		npages++;

		if (npages >= maxpages)	/* don't bother going further */

			return maxpages;

		size -= len;

		offset = 0;

	}

	return min(npages, maxpages);

}



size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,

			 struct iov_iter *i)

{

	if (i->type & ITER_BVEC)

		return copy_page_to_iter_bvec(page, offset, bytes, i);

	else

		return copy_page_to_iter_iovec(page, offset, bytes, i);

}

EXPORT_SYMBOL(copy_page_to_iter);



size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,

			 struct iov_iter *i)

{

	if (i->type & ITER_BVEC)

		return copy_page_from_iter_bvec(page, offset, bytes, i);

	else

		return copy_page_from_iter_iovec(page, offset, bytes, i);

}

EXPORT_SYMBOL(copy_page_from_iter);



size_t iov_iter_copy_from_user_atomic(struct page *page,

		struct iov_iter *i, unsigned long offset, size_t bytes)

{

	if (i->type & ITER_BVEC)

		return copy_from_user_bvec(page, i, offset, bytes);

	else

		return copy_from_user_atomic_iovec(page, i, offset, bytes);

}

EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);



void iov_iter_advance(struct iov_iter *i, size_t size)

{

	if (i->type & ITER_BVEC)

		advance_bvec(i, size);

	else

		advance_iovec(i, size);

}

EXPORT_SYMBOL(iov_iter_advance);



/*

 * Return the count of just the current iov_iter segment.

 */

size_t iov_iter_single_seg_count(const struct iov_iter *i)

{

	if (i->nr_segs == 1)

		return i->count;

	else if (i->type & ITER_BVEC)

		return min(i->count, i->iov->iov_len - i->iov_offset);

	else

		return min(i->count, i->bvec->bv_len - i->iov_offset);

}

EXPORT_SYMBOL(iov_iter_single_seg_count);



unsigned long iov_iter_alignment(const struct iov_iter *i)

{

	if (i->type & ITER_BVEC)

		return alignment_bvec(i);

	else

		return alignment_iovec(i);

}

EXPORT_SYMBOL(iov_iter_alignment);



ssize_t iov_iter_get_pages(struct iov_iter *i,

		   struct page **pages, size_t maxsize,

		   size_t *start)

{

	if (i->type & ITER_BVEC)

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

	else

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

}

EXPORT_SYMBOL(iov_iter_get_pages);



ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,

		   struct page ***pages, size_t maxsize,

		   size_t *start)

{

	if (i->type & ITER_BVEC)

		return get_pages_alloc_bvec(i, pages, maxsize, start);

	else

		return get_pages_alloc_iovec(i, pages, maxsize, start);

}

EXPORT_SYMBOL(iov_iter_get_pages_alloc);



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

{

	if (i->type & ITER_BVEC)

		return iov_iter_npages_bvec(i, maxpages);

	else

		return iov_iter_npages_iovec(i, maxpages);

}

EXPORT_SYMBOL(iov_iter_npages);

mm/page_io.c

+12 −7
Original line number Diff line number Diff line
@@ -259,23 +259,28 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc, 
		struct kiocb kiocb;

		struct file *swap_file = sis->swap_file;

		struct address_space *mapping = swap_file->f_mapping;

		struct iovec iov = {

			.iov_base = kmap(page),

			.iov_len  = PAGE_SIZE,

		struct bio_vec bv = {

			.bv_page = page,

			.bv_len  = PAGE_SIZE,

			.bv_offset = 0

		};

		struct iov_iter from = {

			.type = ITER_BVEC | WRITE,

			.count = PAGE_SIZE,

			.iov_offset = 0,

			.nr_segs = 1,

			.bvec = &bv

		};

		struct iov_iter from;



		init_sync_kiocb(&kiocb, swap_file);

		kiocb.ki_pos = page_file_offset(page);

		kiocb.ki_nbytes = PAGE_SIZE;

		iov_iter_init(&from, KERNEL_WRITE, &iov, 1, PAGE_SIZE);



		set_page_writeback(page);

		unlock_page(page);

		ret = mapping->a_ops->direct_IO(KERNEL_WRITE,

		ret = mapping->a_ops->direct_IO(ITER_BVEC | WRITE,

						&kiocb, &from,

						kiocb.ki_pos);

		kunmap(page);

		if (ret == PAGE_SIZE) {

			count_vm_event(PSWPOUT);

			ret = 0;