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Commit 4a9e5ef1 authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
Browse files

mm: write iovec cleanup 



Hide some of the open-coded nr_segs tests into the iovec helpers.  This is all
to simplify generic_file_buffered_write, because that gets more complex in the
next patch.

Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent eb2be189

mm/filemap.c

+10 −26
Original line number Diff line number Diff line
@@ -1823,12 +1823,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, 
	/*

	 * handle partial DIO write.  Adjust cur_iov if needed.

	 */

	if (likely(nr_segs == 1))

		buf = iov->iov_base + written;

	else {

		filemap_set_next_iovec(&cur_iov, &iov_offset, written);

		buf = cur_iov->iov_base + iov_offset;

	}

	filemap_set_next_iovec(&cur_iov, nr_segs, &iov_offset, written);



	do {

		struct page *page;
@@ -1838,6 +1833,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, 
		size_t bytes;		/* Bytes to write to page */

		size_t copied;		/* Bytes copied from user */



		buf = cur_iov->iov_base + iov_offset;

		offset = (pos & (PAGE_CACHE_SIZE - 1));

		index = pos >> PAGE_CACHE_SHIFT;

		bytes = PAGE_CACHE_SIZE - offset;
@@ -1869,13 +1865,10 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, 
		if (unlikely(status))

			goto fs_write_aop_error;



		if (likely(nr_segs == 1))

		copied = filemap_copy_from_user(page, offset,

							buf, bytes);

		else

			copied = filemap_copy_from_user_iovec(page, offset,

						cur_iov, iov_offset, bytes);

					cur_iov, nr_segs, iov_offset, bytes);

		flush_dcache_page(page);



		status = a_ops->commit_write(file, page, offset, offset+bytes);

		if (unlikely(status < 0 || status == AOP_TRUNCATED_PAGE))

			goto fs_write_aop_error;
@@ -1886,20 +1879,11 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, 
		if (unlikely(status > 0)) /* filesystem did partial write */

			copied = status;



		if (likely(copied > 0)) {

		written += copied;

		count -= copied;

		pos += copied;

			buf += copied;

			if (unlikely(nr_segs > 1)) {

				filemap_set_next_iovec(&cur_iov,

						&iov_offset, copied);

				if (count)

					buf = cur_iov->iov_base + iov_offset;

			} else {

				iov_offset += copied;

			}

		}

		filemap_set_next_iovec(&cur_iov, nr_segs, &iov_offset, copied);



		unlock_page(page);

		mark_page_accessed(page);

		page_cache_release(page);

mm/filemap.h

+50 −50
Original line number Diff line number Diff line
@@ -22,68 +22,67 @@ __filemap_copy_from_user_iovec_inatomic(char *vaddr, 


/*

 * Copy as much as we can into the page and return the number of bytes which

 * were sucessfully copied.  If a fault is encountered then clear the page

 * out to (offset+bytes) and return the number of bytes which were copied.

 *

 * NOTE: For this to work reliably we really want copy_from_user_inatomic_nocache

 * to *NOT* zero any tail of the buffer that it failed to copy.  If it does,

 * and if the following non-atomic copy succeeds, then there is a small window

 * where the target page contains neither the data before the write, nor the

 * data after the write (it contains zero).  A read at this time will see

 * data that is inconsistent with any ordering of the read and the write.

 * (This has been detected in practice).

 * were sucessfully copied.  If a fault is encountered then return the number of

 * bytes which were copied.

 */

static inline size_t

filemap_copy_from_user(struct page *page, unsigned long offset,

			const char __user *buf, unsigned bytes)

filemap_copy_from_user_atomic(struct page *page, unsigned long offset,

			const struct iovec *iov, unsigned long nr_segs,

			size_t base, size_t bytes)

{

	char *kaddr;

	int left;

	size_t copied;



	kaddr = kmap_atomic(page, KM_USER0);

	left = __copy_from_user_inatomic_nocache(kaddr + offset, buf, bytes);

	if (likely(nr_segs == 1)) {

		int left;

		char __user *buf = iov->iov_base + base;

		left = __copy_from_user_inatomic_nocache(kaddr + offset,

							buf, bytes);

		copied = bytes - left;

	} else {

		copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset,

							iov, base, bytes);

	}

	kunmap_atomic(kaddr, KM_USER0);



	if (left != 0) {

		/* Do it the slow way */

		kaddr = kmap(page);

		left = __copy_from_user_nocache(kaddr + offset, buf, bytes);

		kunmap(page);

	}

	return bytes - left;

	return copied;

}



/*

 * This has the same sideeffects and return value as filemap_copy_from_user().

 * The difference is that on a fault we need to memset the remainder of the

 * page (out to offset+bytes), to emulate filemap_copy_from_user()'s

 * single-segment behaviour.

 * This has the same sideeffects and return value as

 * filemap_copy_from_user_atomic().

 * The difference is that it attempts to resolve faults.

 */

static inline size_t

filemap_copy_from_user_iovec(struct page *page, unsigned long offset,

			const struct iovec *iov, size_t base, size_t bytes)

filemap_copy_from_user(struct page *page, unsigned long offset,

			const struct iovec *iov, unsigned long nr_segs,

			 size_t base, size_t bytes)

{

	char *kaddr;

	size_t copied;



	kaddr = kmap_atomic(page, KM_USER0);

	copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov,

							 base, bytes);

	kunmap_atomic(kaddr, KM_USER0);

	if (copied != bytes) {

	kaddr = kmap(page);

		copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov,

								 base, bytes);

		if (bytes - copied)

			memset(kaddr + offset + copied, 0, bytes - copied);

		kunmap(page);

	if (likely(nr_segs == 1)) {

		int left;

		char __user *buf = iov->iov_base + base;

		left = __copy_from_user_nocache(kaddr + offset, buf, bytes);

		copied = bytes - left;

	} else {

		copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset,

							iov, base, bytes);

	}

	kunmap(page);

	return copied;

}



static inline void

filemap_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes)

filemap_set_next_iovec(const struct iovec **iovp, unsigned long nr_segs,

						 size_t *basep, size_t bytes)

{

	if (likely(nr_segs == 1)) {

		*basep += bytes;

	} else {

		const struct iovec *iov = *iovp;

		size_t base = *basep;
@@ -100,4 +99,5 @@ filemap_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes) 
		*iovp = iov;

		*basep = base;

	}

}

#endif

mm/filemap_xip.c

+7 −10
Original line number Diff line number Diff line
@@ -15,7 +15,6 @@ 
#include <linux/rmap.h>

#include <linux/sched.h>

#include <asm/tlbflush.h>

#include "filemap.h"



/*

 * We do use our own empty page to avoid interference with other users
@@ -288,6 +287,7 @@ __xip_file_write(struct file *filp, const char __user *buf, 
		unsigned long index;

		unsigned long offset;

		size_t copied;

		char *kaddr;



		offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */

		index = pos >> PAGE_CACHE_SHIFT;
@@ -295,14 +295,6 @@ __xip_file_write(struct file *filp, const char __user *buf, 
		if (bytes > count)

			bytes = count;



		/*

		 * Bring in the user page that we will copy from _first_.

		 * Otherwise there's a nasty deadlock on copying from the

		 * same page as we're writing to, without it being marked

		 * up-to-date.

		 */

		fault_in_pages_readable(buf, bytes);



		page = a_ops->get_xip_page(mapping,

					   index*(PAGE_SIZE/512), 0);

		if (IS_ERR(page) && (PTR_ERR(page) == -ENODATA)) {
@@ -319,8 +311,13 @@ __xip_file_write(struct file *filp, const char __user *buf, 
			break;

		}



		copied = filemap_copy_from_user(page, offset, buf, bytes);

		fault_in_pages_readable(buf, bytes);

		kaddr = kmap_atomic(page, KM_USER0);

		copied = bytes -

			__copy_from_user_inatomic_nocache(kaddr, buf, bytes);

		kunmap_atomic(kaddr, KM_USER0);

		flush_dcache_page(page);



		if (likely(copied > 0)) {

			status = copied;