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Commit 01f2705d authored by Nate Diller's avatar Nate Diller Committed by Linus Torvalds
Browse files

fs: convert core functions to zero_user_page 



It's very common for file systems to need to zero part or all of a page,
the simplist way is just to use kmap_atomic() and memset().  There's
actually a library function in include/linux/highmem.h that does exactly
that, but it's confusingly named memclear_highpage_flush(), which is
descriptive of *how* it does the work rather than what the *purpose* is.
So this patchset renames the function to zero_user_page(), and calls it
from the various places that currently open code it.

This first patch introduces the new function call, and converts all the
core kernel callsites, both the open-coded ones and the old
memclear_highpage_flush() ones.  Following this patch is a series of
conversions for each file system individually, per AKPM, and finally a
patch deprecating the old call.  The diffstat below shows the entire
patchset.

[akpm@linux-foundation.org: fix a few things]
Signed-off-by: default avatarNate Diller <nate.diller@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 38a23e31

drivers/block/loop.c

+1 −5
Original line number Diff line number Diff line
@@ -243,17 +243,13 @@ static int do_lo_send_aops(struct loop_device *lo, struct bio_vec *bvec, 
		transfer_result = lo_do_transfer(lo, WRITE, page, offset,

				bvec->bv_page, bv_offs, size, IV);

		if (unlikely(transfer_result)) {

			char *kaddr;



			/*

			 * The transfer failed, but we still write the data to

			 * keep prepare/commit calls balanced.

			 */

			printk(KERN_ERR "loop: transfer error block %llu\n",

			       (unsigned long long)index);

			kaddr = kmap_atomic(page, KM_USER0);

			memset(kaddr + offset, 0, size);

			kunmap_atomic(kaddr, KM_USER0);

			zero_user_page(page, offset, size, KM_USER0);

		}

		flush_dcache_page(page);

		ret = aops->commit_write(file, page, offset,

fs/buffer.c

+12 −44
Original line number Diff line number Diff line
@@ -1846,13 +1846,8 @@ static int __block_prepare_write(struct inode *inode, struct page *page, 
		if (block_start >= to)

			break;

		if (buffer_new(bh)) {

			void *kaddr;



			clear_buffer_new(bh);

			kaddr = kmap_atomic(page, KM_USER0);

			memset(kaddr+block_start, 0, bh->b_size);

			flush_dcache_page(page);

			kunmap_atomic(kaddr, KM_USER0);

			zero_user_page(page, block_start, bh->b_size, KM_USER0);

			set_buffer_uptodate(bh);

			mark_buffer_dirty(bh);

		}
@@ -1940,10 +1935,8 @@ int block_read_full_page(struct page *page, get_block_t *get_block) 
					SetPageError(page);

			}

			if (!buffer_mapped(bh)) {

				void *kaddr = kmap_atomic(page, KM_USER0);

				memset(kaddr + i * blocksize, 0, blocksize);

				flush_dcache_page(page);

				kunmap_atomic(kaddr, KM_USER0);

				zero_user_page(page, i * blocksize, blocksize,

						KM_USER0);

				if (!err)

					set_buffer_uptodate(bh);

				continue;
@@ -2086,7 +2079,6 @@ int cont_prepare_write(struct page *page, unsigned offset, 
	long status;

	unsigned zerofrom;

	unsigned blocksize = 1 << inode->i_blkbits;

	void *kaddr;



	while(page->index > (pgpos = *bytes>>PAGE_CACHE_SHIFT)) {

		status = -ENOMEM;
@@ -2108,10 +2100,8 @@ int cont_prepare_write(struct page *page, unsigned offset, 
						PAGE_CACHE_SIZE, get_block);

		if (status)

			goto out_unmap;

		kaddr = kmap_atomic(new_page, KM_USER0);

		memset(kaddr+zerofrom, 0, PAGE_CACHE_SIZE-zerofrom);

		flush_dcache_page(new_page);

		kunmap_atomic(kaddr, KM_USER0);

		zero_user_page(page, zerofrom, PAGE_CACHE_SIZE - zerofrom,

				KM_USER0);

		generic_commit_write(NULL, new_page, zerofrom, PAGE_CACHE_SIZE);

		unlock_page(new_page);

		page_cache_release(new_page);
@@ -2138,10 +2128,7 @@ int cont_prepare_write(struct page *page, unsigned offset, 
	if (status)

		goto out1;

	if (zerofrom < offset) {

		kaddr = kmap_atomic(page, KM_USER0);

		memset(kaddr+zerofrom, 0, offset-zerofrom);

		flush_dcache_page(page);

		kunmap_atomic(kaddr, KM_USER0);

		zero_user_page(page, zerofrom, offset - zerofrom, KM_USER0);

		__block_commit_write(inode, page, zerofrom, offset);

	}

	return 0;
@@ -2340,10 +2327,7 @@ int nobh_prepare_write(struct page *page, unsigned from, unsigned to, 
	 * Error recovery is pretty slack.  Clear the page and mark it dirty

	 * so we'll later zero out any blocks which _were_ allocated.

	 */

	kaddr = kmap_atomic(page, KM_USER0);

	memset(kaddr, 0, PAGE_CACHE_SIZE);

	flush_dcache_page(page);

	kunmap_atomic(kaddr, KM_USER0);

	zero_user_page(page, 0, PAGE_CACHE_SIZE, KM_USER0);

	SetPageUptodate(page);

	set_page_dirty(page);

	return ret;
@@ -2382,7 +2366,6 @@ int nobh_writepage(struct page *page, get_block_t *get_block, 
	loff_t i_size = i_size_read(inode);

	const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;

	unsigned offset;

	void *kaddr;

	int ret;



	/* Is the page fully inside i_size? */
@@ -2413,10 +2396,7 @@ int nobh_writepage(struct page *page, get_block_t *get_block, 
	 * the  page size, the remaining memory is zeroed when mapped, and

	 * writes to that region are not written out to the file."

	 */

	kaddr = kmap_atomic(page, KM_USER0);

	memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);

	flush_dcache_page(page);

	kunmap_atomic(kaddr, KM_USER0);

	zero_user_page(page, offset, PAGE_CACHE_SIZE - offset, KM_USER0);

out:

	ret = mpage_writepage(page, get_block, wbc);

	if (ret == -EAGAIN)
@@ -2437,7 +2417,6 @@ int nobh_truncate_page(struct address_space *mapping, loff_t from) 
	unsigned to;

	struct page *page;

	const struct address_space_operations *a_ops = mapping->a_ops;

	char *kaddr;

	int ret = 0;



	if ((offset & (blocksize - 1)) == 0)
@@ -2451,10 +2430,8 @@ int nobh_truncate_page(struct address_space *mapping, loff_t from) 
	to = (offset + blocksize) & ~(blocksize - 1);

	ret = a_ops->prepare_write(NULL, page, offset, to);

	if (ret == 0) {

		kaddr = kmap_atomic(page, KM_USER0);

		memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);

		flush_dcache_page(page);

		kunmap_atomic(kaddr, KM_USER0);

		zero_user_page(page, offset, PAGE_CACHE_SIZE - offset,

				KM_USER0);

		/*

		 * It would be more correct to call aops->commit_write()

		 * here, but this is more efficient.
@@ -2480,7 +2457,6 @@ int block_truncate_page(struct address_space *mapping, 
	struct inode *inode = mapping->host;

	struct page *page;

	struct buffer_head *bh;

	void *kaddr;

	int err;



	blocksize = 1 << inode->i_blkbits;
@@ -2534,11 +2510,7 @@ int block_truncate_page(struct address_space *mapping, 
			goto unlock;

	}



	kaddr = kmap_atomic(page, KM_USER0);

	memset(kaddr + offset, 0, length);

	flush_dcache_page(page);

	kunmap_atomic(kaddr, KM_USER0);



	zero_user_page(page, offset, length, KM_USER0);

	mark_buffer_dirty(bh);

	err = 0;
@@ -2559,7 +2531,6 @@ int block_write_full_page(struct page *page, get_block_t *get_block, 
	loff_t i_size = i_size_read(inode);

	const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;

	unsigned offset;

	void *kaddr;



	/* Is the page fully inside i_size? */

	if (page->index < end_index)
@@ -2585,10 +2556,7 @@ int block_write_full_page(struct page *page, get_block_t *get_block, 
	 * the  page size, the remaining memory is zeroed when mapped, and

	 * writes to that region are not written out to the file."

	 */

	kaddr = kmap_atomic(page, KM_USER0);

	memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);

	flush_dcache_page(page);

	kunmap_atomic(kaddr, KM_USER0);

	zero_user_page(page, offset, PAGE_CACHE_SIZE - offset, KM_USER0);

	return __block_write_full_page(inode, page, get_block, wbc);

}

fs/direct-io.c

+2 −6
Original line number Diff line number Diff line
@@ -867,7 +867,6 @@ static int do_direct_IO(struct dio *dio) 
do_holes:

			/* Handle holes */

			if (!buffer_mapped(map_bh)) {

				char *kaddr;

				loff_t i_size_aligned;



				/* AKPM: eargh, -ENOTBLK is a hack */
@@ -888,11 +887,8 @@ static int do_direct_IO(struct dio *dio) 
					page_cache_release(page);

					goto out;

				}

				kaddr = kmap_atomic(page, KM_USER0);

				memset(kaddr + (block_in_page << blkbits),

						0, 1 << blkbits);

				flush_dcache_page(page);

				kunmap_atomic(kaddr, KM_USER0);

				zero_user_page(page, block_in_page << blkbits,

						1 << blkbits, KM_USER0);

				dio->block_in_file++;

				block_in_page++;

				goto next_block;

fs/mpage.c

+5 −10
Original line number Diff line number Diff line
@@ -284,11 +284,9 @@ do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages, 
	}



	if (first_hole != blocks_per_page) {

		char *kaddr = kmap_atomic(page, KM_USER0);

		memset(kaddr + (first_hole << blkbits), 0,

				PAGE_CACHE_SIZE - (first_hole << blkbits));

		flush_dcache_page(page);

		kunmap_atomic(kaddr, KM_USER0);

		zero_user_page(page, first_hole << blkbits,

				PAGE_CACHE_SIZE - (first_hole << blkbits),

				KM_USER0);

		if (first_hole == 0) {

			SetPageUptodate(page);

			unlock_page(page);
@@ -576,14 +574,11 @@ __mpage_writepage(struct bio *bio, struct page *page, get_block_t get_block, 
		 * written out to the file."

		 */

		unsigned offset = i_size & (PAGE_CACHE_SIZE - 1);

		char *kaddr;



		if (page->index > end_index || !offset)

			goto confused;

		kaddr = kmap_atomic(page, KM_USER0);

		memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);

		flush_dcache_page(page);

		kunmap_atomic(kaddr, KM_USER0);

		zero_user_page(page, offset, PAGE_CACHE_SIZE - offset,

				KM_USER0);

	}



	/*

include/linux/highmem.h

+19 −9
Original line number Diff line number Diff line
@@ -94,17 +94,27 @@ static inline void clear_highpage(struct page *page) 


/*

 * Same but also flushes aliased cache contents to RAM.

 *

 * This must be a macro because KM_USER0 and friends aren't defined if

 * !CONFIG_HIGHMEM

 */

static inline void memclear_highpage_flush(struct page *page, unsigned int offset, unsigned int size)

#define zero_user_page(page, offset, size, km_type)		\

	do {							\

		void *kaddr;					\

								\

		BUG_ON((offset) + (size) > PAGE_SIZE);		\

								\

		kaddr = kmap_atomic(page, km_type);		\

		memset((char *)kaddr + (offset), 0, (size));	\

		flush_dcache_page(page);			\

		kunmap_atomic(kaddr, (km_type));		\

	} while (0)





static inline void memclear_highpage_flush(struct page *page,

			unsigned int offset, unsigned int size)

{

	void *kaddr;



	BUG_ON(offset + size > PAGE_SIZE);



	kaddr = kmap_atomic(page, KM_USER0);

	memset((char *)kaddr + offset, 0, size);

	flush_dcache_page(page);

	kunmap_atomic(kaddr, KM_USER0);

	zero_user_page(page, offset, size, KM_USER0);

}



#ifndef __HAVE_ARCH_COPY_USER_HIGHPAGE