Pagecache zeroing: zero_user_segment, zero_user_segments and zero_user

From: Christoph Lameter
Date: Tue May 15 2007 - 23:00:45 EST

Simplify page cache zeroing of segments of pages through 3 functions


zero_user_segments(page, start1, end1, start2, end2)

Zeros two segments of the page. It takes the position where to
start and end the zeroing which avoids length calculations.

zero_user_segment(page, start, end)

Same for a single segment.

zero_user(page, start, length)

Length variant for the case where we know the length.



We remove the zero_user_page macro. Issues:

1. Its a macro. Inline functions are preferable.

2. It has a useless parameter specifying the kmap slot.
The functions above default to KM_USER0 which is also always used when
zero_user_page was called except in one single case. We open code that
single case to draw attention to the spot.

Signed-off-by: Christoph Lameter <clameter@xxxxxxx>

---
drivers/block/loop.c | 2 -
fs/affs/file.c | 2 -
fs/buffer.c | 48 ++++++++++++++---------------------------------
fs/direct-io.c | 4 +--
fs/ext3/inode.c | 4 +--
fs/libfs.c | 11 +++-------
fs/mpage.c | 7 +-----
fs/ntfs/aops.c | 18 +++++++++--------
fs/ntfs/file.c | 32 ++++++++++++++-----------------
fs/reiserfs/file.c | 17 ++++------------
fs/reiserfs/inode.c | 4 +--
include/linux/highmem.h | 49 ++++++++++++++++++++++++++++++------------------
mm/filemap_xip.c | 2 -
mm/truncate.c | 2 -
14 files changed, 92 insertions(+), 110 deletions(-)

Index: vps/include/linux/highmem.h
===================================================================
--- vps.orig/include/linux/highmem.h 2007-05-15 18:17:51.000000000 -0700
+++ vps/include/linux/highmem.h 2007-05-15 19:47:32.000000000 -0700
@@ -92,28 +92,41 @@ static inline void clear_highpage(struct
kunmap_atomic(kaddr, KM_USER0);
}

-/*
- * 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
- */
-#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 zero_user_segments(struct page *page,
+ unsigned start1, unsigned end1,
+ unsigned start2, unsigned end2)
+{
+ void *kaddr = kmap_atomic(page, KM_USER0);
+
+ BUG_ON(end1 > PAGE_SIZE ||
+ end2 > PAGE_SIZE);
+
+ if (end1 > start1)
+ memset(kaddr + start1, 0, end1 - start1);
+
+ if (end2 > start2)
+ memset(kaddr + start2, 0, end2 - start2);
+
+ flush_dcache_page(page);
+ kunmap_atomic(kaddr, KM_USER0);
+}
+
+static inline void zero_user_segment(struct page *page,
+ unsigned start, unsigned end)
+{
+ zero_user_segments(page, start, end, 0, 0);
+}
+
+static inline void zero_user(struct page *page,
+ unsigned start, unsigned size)
+{
+ zero_user_segments(page, start, start + size, 0, 0);
+}

static inline void __deprecated memclear_highpage_flush(struct page *page,
unsigned int offset, unsigned int size)
{
- zero_user_page(page, offset, size, KM_USER0);
+ zero_user(page, offset, size);
}

#ifndef __HAVE_ARCH_COPY_USER_HIGHPAGE
Index: vps/fs/buffer.c
===================================================================
--- vps.orig/fs/buffer.c 2007-05-15 19:04:01.000000000 -0700
+++ vps/fs/buffer.c 2007-05-15 19:22:37.000000000 -0700
@@ -1787,19 +1787,10 @@ static int __block_prepare_write(struct
set_buffer_uptodate(bh);
continue;
}
- if (block_end > to || block_start < from) {
- void *kaddr;
-
- kaddr = kmap_atomic(page, KM_USER0);
- if (block_end > to)
- memset(kaddr+to, 0,
- block_end-to);
- if (block_start < from)
- memset(kaddr+block_start,
- 0, from-block_start);
- flush_dcache_page(page);
- kunmap_atomic(kaddr, KM_USER0);
- }
+ if (block_end > to || block_start < from)
+ zero_user_segments(page,
+ to, block_end,
+ block_start, from);
continue;
}
}
@@ -1847,7 +1838,7 @@ static int __block_prepare_write(struct
break;
if (buffer_new(bh)) {
clear_buffer_new(bh);
- zero_user_page(page, block_start, bh->b_size, KM_USER0);
+ zero_user(page, block_start, bh->b_size);
set_buffer_uptodate(bh);
mark_buffer_dirty(bh);
}
@@ -1935,8 +1926,7 @@ int block_read_full_page(struct page *pa
SetPageError(page);
}
if (!buffer_mapped(bh)) {
- zero_user_page(page, i * blocksize, blocksize,
- KM_USER0);
+ zero_user(page, i * blocksize, blocksize);
if (!err)
set_buffer_uptodate(bh);
continue;
@@ -2100,8 +2090,7 @@ int cont_prepare_write(struct page *page
PAGE_CACHE_SIZE, get_block);
if (status)
goto out_unmap;
- zero_user_page(page, zerofrom, PAGE_CACHE_SIZE - zerofrom,
- KM_USER0);
+ zero_user_segment(page, zerofrom, PAGE_CACHE_SIZE);
generic_commit_write(NULL, new_page, zerofrom, PAGE_CACHE_SIZE);
unlock_page(new_page);
page_cache_release(new_page);
@@ -2128,7 +2117,7 @@ int cont_prepare_write(struct page *page
if (status)
goto out1;
if (zerofrom < offset) {
- zero_user_page(page, zerofrom, offset - zerofrom, KM_USER0);
+ zero_user_segment(page, zerofrom, offset);
__block_commit_write(inode, page, zerofrom, offset);
}
return 0;
@@ -2215,7 +2204,6 @@ int nobh_prepare_write(struct page *page
unsigned block_in_page;
unsigned block_start;
sector_t block_in_file;
- char *kaddr;
int nr_reads = 0;
int i;
int ret = 0;
@@ -2255,13 +2243,8 @@ int nobh_prepare_write(struct page *page
if (PageUptodate(page))
continue;
if (buffer_new(&map_bh) || !buffer_mapped(&map_bh)) {
- kaddr = kmap_atomic(page, KM_USER0);
- if (block_start < from)
- memset(kaddr+block_start, 0, from-block_start);
- if (block_end > to)
- memset(kaddr + to, 0, block_end - to);
- flush_dcache_page(page);
- kunmap_atomic(kaddr, KM_USER0);
+ zero_user_segments(page, block_start, from,
+ to, block_end);
continue;
}
if (buffer_uptodate(&map_bh))
@@ -2327,7 +2310,7 @@ failed:
* Error recovery is pretty slack. Clear the page and mark it dirty
* so we'll later zero out any blocks which _were_ allocated.
*/
- zero_user_page(page, 0, PAGE_CACHE_SIZE, KM_USER0);
+ zero_user_segment(page, 0, PAGE_CACHE_SIZE);
SetPageUptodate(page);
set_page_dirty(page);
return ret;
@@ -2396,7 +2379,7 @@ int nobh_writepage(struct page *page, ge
* the page size, the remaining memory is zeroed when mapped, and
* writes to that region are not written out to the file."
*/
- zero_user_page(page, offset, PAGE_CACHE_SIZE - offset, KM_USER0);
+ zero_user_segment(page, offset, PAGE_CACHE_SIZE);
out:
ret = mpage_writepage(page, get_block, wbc);
if (ret == -EAGAIN)
@@ -2430,8 +2413,7 @@ int nobh_truncate_page(struct address_sp
to = (offset + blocksize) & ~(blocksize - 1);
ret = a_ops->prepare_write(NULL, page, offset, to);
if (ret == 0) {
- zero_user_page(page, offset, PAGE_CACHE_SIZE - offset,
- KM_USER0);
+ zero_user_segment(page, offset, PAGE_CACHE_SIZE);
/*
* It would be more correct to call aops->commit_write()
* here, but this is more efficient.
@@ -2510,7 +2492,7 @@ int block_truncate_page(struct address_s
goto unlock;
}

- zero_user_page(page, offset, length, KM_USER0);
+ zero_user(page, offset, length);
mark_buffer_dirty(bh);
err = 0;

@@ -2556,7 +2538,7 @@ int block_write_full_page(struct page *p
* the page size, the remaining memory is zeroed when mapped, and
* writes to that region are not written out to the file."
*/
- zero_user_page(page, offset, PAGE_CACHE_SIZE - offset, KM_USER0);
+ zero_user_segment(page, offset, PAGE_CACHE_SIZE);
return __block_write_full_page(inode, page, get_block, wbc);
}

Index: vps/fs/libfs.c
===================================================================
--- vps.orig/fs/libfs.c 2007-05-15 19:04:01.000000000 -0700
+++ vps/fs/libfs.c 2007-05-15 19:17:59.000000000 -0700
@@ -340,13 +340,10 @@ int simple_prepare_write(struct file *fi
unsigned from, unsigned to)
{
if (!PageUptodate(page)) {
- if (to - from != PAGE_CACHE_SIZE) {
- void *kaddr = kmap_atomic(page, KM_USER0);
- memset(kaddr, 0, from);
- memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
- flush_dcache_page(page);
- kunmap_atomic(kaddr, KM_USER0);
- }
+ if (to - from != PAGE_CACHE_SIZE)
+ zero_user_segments(page,
+ 0, from,
+ to, PAGE_CACHE_SIZE);
}
return 0;
}
Index: vps/fs/reiserfs/file.c
===================================================================
--- vps.orig/fs/reiserfs/file.c 2007-05-15 19:04:01.000000000 -0700
+++ vps/fs/reiserfs/file.c 2007-05-15 19:17:59.000000000 -0700
@@ -1059,13 +1059,7 @@ static int reiserfs_prepare_file_region_
maping blocks, since there is none, so we just zero out remaining
parts of first and last pages in write area (if needed) */
if ((pos & ~((loff_t) PAGE_CACHE_SIZE - 1)) > inode->i_size) {
- if (from != 0) /* First page needs to be partially zeroed */
- zero_user_page(prepared_pages[0], 0, from, KM_USER0);
-
- if (to != PAGE_CACHE_SIZE) /* Last page needs to be partially zeroed */
- zero_user_page(prepared_pages[num_pages-1], to,
- PAGE_CACHE_SIZE - to, KM_USER0);
-
+ zero_user_segments(prepared_pages[0], 0, from, to, PAGE_CACHE_SIZE);
/* Since all blocks are new - use already calculated value */
return blocks;
}
@@ -1191,9 +1185,8 @@ static int reiserfs_prepare_file_region_
ll_rw_block(READ, 1, &bh);
*wait_bh++ = bh;
} else { /* Not mapped, zero it */
- zero_user_page(prepared_pages[0],
- block_start,
- from - block_start, KM_USER0);
+ zero_user_segment(prepared_pages[0],
+ block_start, from);
set_buffer_uptodate(bh);
}
}
@@ -1225,8 +1218,8 @@ static int reiserfs_prepare_file_region_
ll_rw_block(READ, 1, &bh);
*wait_bh++ = bh;
} else { /* Not mapped, zero it */
- zero_user_page(prepared_pages[num_pages-1],
- to, block_end - to, KM_USER0);
+ zero_user_segment(prepared_pages[num_pages-1],
+ to, block_end);
set_buffer_uptodate(bh);
}
}
Index: vps/fs/affs/file.c
===================================================================
--- vps.orig/fs/affs/file.c 2007-05-15 19:03:28.000000000 -0700
+++ vps/fs/affs/file.c 2007-05-15 19:20:36.000000000 -0700
@@ -628,7 +628,7 @@ static int affs_prepare_write_ofs(struct
return err;
}
if (to < PAGE_CACHE_SIZE) {
- zero_user_page(page, to, PAGE_CACHE_SIZE - to, KM_USER0);
+ zero_user_segment(page, to, PAGE_CACHE_SIZE);
if (size > offset + to) {
if (size < offset + PAGE_CACHE_SIZE)
tmp = size & ~PAGE_CACHE_MASK;
Index: vps/fs/mpage.c
===================================================================
--- vps.orig/fs/mpage.c 2007-05-15 19:03:28.000000000 -0700
+++ vps/fs/mpage.c 2007-05-15 19:20:36.000000000 -0700
@@ -284,9 +284,7 @@ do_mpage_readpage(struct bio *bio, struc
}

if (first_hole != blocks_per_page) {
- zero_user_page(page, first_hole << blkbits,
- PAGE_CACHE_SIZE - (first_hole << blkbits),
- KM_USER0);
+ zero_user_segment(page, first_hole << blkbits, PAGE_CACHE_SIZE);
if (first_hole == 0) {
SetPageUptodate(page);
unlock_page(page);
@@ -585,8 +583,7 @@ page_is_mapped:

if (page->index > end_index || !offset)
goto confused;
- zero_user_page(page, offset, PAGE_CACHE_SIZE - offset,
- KM_USER0);
+ zero_user_segment(page, offset, PAGE_CACHE_SIZE);
}

/*
Index: vps/fs/ntfs/aops.c
===================================================================
--- vps.orig/fs/ntfs/aops.c 2007-05-15 19:03:28.000000000 -0700
+++ vps/fs/ntfs/aops.c 2007-05-15 19:32:04.000000000 -0700
@@ -87,13 +87,17 @@ static void ntfs_end_buffer_async_read(s
/* Check for the current buffer head overflowing. */
if (unlikely(file_ofs + bh->b_size > init_size)) {
int ofs;
+ void *kaddr;

ofs = 0;
if (file_ofs < init_size)
ofs = init_size - file_ofs;
local_irq_save(flags);
- zero_user_page(page, bh_offset(bh) + ofs,
- bh->b_size - ofs, KM_BIO_SRC_IRQ);
+ kaddr = kmap_atomic(page, KM_BIO_SRC_IRQ);
+ memset(kaddr + bh_offset(bh) + ofs, 0,
+ bh->b_size - ofs);
+ flush_dcache_page(page);
+ kunmap_atomic(kaddr, KM_BIO_SRC_IRQ);
local_irq_restore(flags);
}
} else {
@@ -334,7 +338,7 @@ handle_hole:
bh->b_blocknr = -1UL;
clear_buffer_mapped(bh);
handle_zblock:
- zero_user_page(page, i * blocksize, blocksize, KM_USER0);
+ zero_user(page, i * blocksize, blocksize);
if (likely(!err))
set_buffer_uptodate(bh);
} while (i++, iblock++, (bh = bh->b_this_page) != head);
@@ -451,7 +455,7 @@ retry_readpage:
* ok to ignore the compressed flag here.
*/
if (unlikely(page->index > 0)) {
- zero_user_page(page, 0, PAGE_CACHE_SIZE, KM_USER0);
+ zero_user(page, 0, PAGE_CACHE_SIZE);
goto done;
}
if (!NInoAttr(ni))
@@ -780,8 +784,7 @@ lock_retry_remap:
if (err == -ENOENT || lcn == LCN_ENOENT) {
bh->b_blocknr = -1;
clear_buffer_dirty(bh);
- zero_user_page(page, bh_offset(bh), blocksize,
- KM_USER0);
+ zero_user(page, bh_offset(bh), blocksize);
set_buffer_uptodate(bh);
err = 0;
continue;
@@ -1406,8 +1409,7 @@ retry_writepage:
if (page->index >= (i_size >> PAGE_CACHE_SHIFT)) {
/* The page straddles i_size. */
unsigned int ofs = i_size & ~PAGE_CACHE_MASK;
- zero_user_page(page, ofs, PAGE_CACHE_SIZE - ofs,
- KM_USER0);
+ zero_user_segment(page, ofs, PAGE_CACHE_SIZE);
}
/* Handle mst protected attributes. */
if (NInoMstProtected(ni))
Index: vps/fs/reiserfs/inode.c
===================================================================
--- vps.orig/fs/reiserfs/inode.c 2007-05-15 19:03:28.000000000 -0700
+++ vps/fs/reiserfs/inode.c 2007-05-15 19:29:14.000000000 -0700
@@ -2149,7 +2149,7 @@ int reiserfs_truncate_file(struct inode
/* if we are not on a block boundary */
if (length) {
length = blocksize - length;
- zero_user_page(page, offset, length, KM_USER0);
+ zero_user(page, offset, length);
if (buffer_mapped(bh) && bh->b_blocknr != 0) {
mark_buffer_dirty(bh);
}
@@ -2373,7 +2373,7 @@ static int reiserfs_write_full_page(stru
unlock_page(page);
return 0;
}
- zero_user_page(page, last_offset, PAGE_CACHE_SIZE - last_offset, KM_USER0);
+ zero_user_segment(page, last_offset, PAGE_CACHE_SIZE);
}
bh = head;
block = page->index << (PAGE_CACHE_SHIFT - s->s_blocksize_bits);
Index: vps/mm/truncate.c
===================================================================
--- vps.orig/mm/truncate.c 2007-05-15 19:03:28.000000000 -0700
+++ vps/mm/truncate.c 2007-05-15 19:20:36.000000000 -0700
@@ -47,7 +47,7 @@ void do_invalidatepage(struct page *page

static inline void truncate_partial_page(struct page *page, unsigned partial)
{
- zero_user_page(page, partial, PAGE_CACHE_SIZE - partial, KM_USER0);
+ zero_user_segment(page, partial, PAGE_CACHE_SIZE);
if (PagePrivate(page))
do_invalidatepage(page, partial);
}
Index: vps/fs/direct-io.c
===================================================================
--- vps.orig/fs/direct-io.c 2007-05-15 19:22:52.000000000 -0700
+++ vps/fs/direct-io.c 2007-05-15 19:23:07.000000000 -0700
@@ -887,8 +887,8 @@ do_holes:
page_cache_release(page);
goto out;
}
- zero_user_page(page, block_in_page << blkbits,
- 1 << blkbits, KM_USER0);
+ zero_user(page, block_in_page << blkbits,
+ 1 << blkbits);
dio->block_in_file++;
block_in_page++;
goto next_block;
Index: vps/mm/filemap_xip.c
===================================================================
--- vps.orig/mm/filemap_xip.c 2007-05-15 19:23:32.000000000 -0700
+++ vps/mm/filemap_xip.c 2007-05-15 19:23:41.000000000 -0700
@@ -457,7 +457,7 @@ xip_truncate_page(struct address_space *
else
return PTR_ERR(page);
}
- zero_user_page(page, offset, length, KM_USER0);
+ zero_user(page, offset, length);
return 0;
}
EXPORT_SYMBOL_GPL(xip_truncate_page);
Index: vps/drivers/block/loop.c
===================================================================
--- vps.orig/drivers/block/loop.c 2007-05-15 19:24:52.000000000 -0700
+++ vps/drivers/block/loop.c 2007-05-15 19:25:02.000000000 -0700
@@ -249,7 +249,7 @@ static int do_lo_send_aops(struct loop_d
*/
printk(KERN_ERR "loop: transfer error block %llu\n",
(unsigned long long)index);
- zero_user_page(page, offset, size, KM_USER0);
+ zero_user(page, offset, size);
}
flush_dcache_page(page);
ret = aops->commit_write(file, page, offset,
Index: vps/fs/ext3/inode.c
===================================================================
--- vps.orig/fs/ext3/inode.c 2007-05-15 19:25:07.000000000 -0700
+++ vps/fs/ext3/inode.c 2007-05-15 19:25:43.000000000 -0700
@@ -1778,7 +1778,7 @@ static int ext3_block_truncate_page(hand
*/
if (!page_has_buffers(page) && test_opt(inode->i_sb, NOBH) &&
ext3_should_writeback_data(inode) && PageUptodate(page)) {
- zero_user_page(page, offset, length, KM_USER0);
+ zero_user(page, offset, length);
set_page_dirty(page);
goto unlock;
}
@@ -1831,7 +1831,7 @@ static int ext3_block_truncate_page(hand
goto unlock;
}

- zero_user_page(page, offset, length, KM_USER0);
+ zero_user(page, offset, length);
BUFFER_TRACE(bh, "zeroed end of block");

err = 0;
Index: vps/fs/ntfs/file.c
===================================================================
--- vps.orig/fs/ntfs/file.c 2007-05-15 19:26:53.000000000 -0700
+++ vps/fs/ntfs/file.c 2007-05-15 19:30:08.000000000 -0700
@@ -606,8 +606,8 @@ do_next_page:
ntfs_submit_bh_for_read(bh);
*wait_bh++ = bh;
} else {
- zero_user_page(page, bh_offset(bh),
- blocksize, KM_USER0);
+ zero_user(page, bh_offset(bh),
+ blocksize);
set_buffer_uptodate(bh);
}
}
@@ -682,9 +682,8 @@ map_buffer_cached:
ntfs_submit_bh_for_read(bh);
*wait_bh++ = bh;
} else {
- zero_user_page(page,
- bh_offset(bh),
- blocksize, KM_USER0);
+ zero_user(page, bh_offset(bh),
+ blocksize);
set_buffer_uptodate(bh);
}
}
@@ -702,8 +701,8 @@ map_buffer_cached:
*/
if (bh_end <= pos || bh_pos >= end) {
if (!buffer_uptodate(bh)) {
- zero_user_page(page, bh_offset(bh),
- blocksize, KM_USER0);
+ zero_user(page, bh_offset(bh),
+ blocksize);
set_buffer_uptodate(bh);
}
mark_buffer_dirty(bh);
@@ -742,8 +741,7 @@ map_buffer_cached:
if (!buffer_uptodate(bh))
set_buffer_uptodate(bh);
} else if (!buffer_uptodate(bh)) {
- zero_user_page(page, bh_offset(bh), blocksize,
- KM_USER0);
+ zero_user(page, bh_offset(bh), blocksize);
set_buffer_uptodate(bh);
}
continue;
@@ -867,8 +865,8 @@ rl_not_mapped_enoent:
if (!buffer_uptodate(bh))
set_buffer_uptodate(bh);
} else if (!buffer_uptodate(bh)) {
- zero_user_page(page, bh_offset(bh),
- blocksize, KM_USER0);
+ zero_user(page, bh_offset(bh),
+ blocksize);
set_buffer_uptodate(bh);
}
continue;
@@ -1127,8 +1125,8 @@ rl_not_mapped_enoent:

if (likely(bh_pos < initialized_size))
ofs = initialized_size - bh_pos;
- zero_user_page(page, bh_offset(bh) + ofs,
- blocksize - ofs, KM_USER0);
+ zero_user_segment(page, bh_offset(bh) + ofs,
+ blocksize);
}
} else /* if (unlikely(!buffer_uptodate(bh))) */
err = -EIO;
@@ -1268,8 +1266,8 @@ rl_not_mapped_enoent:
if (PageUptodate(page))
set_buffer_uptodate(bh);
else {
- zero_user_page(page, bh_offset(bh),
- blocksize, KM_USER0);
+ zero_user(page, bh_offset(bh),
+ blocksize);
set_buffer_uptodate(bh);
}
}
@@ -1329,7 +1327,7 @@ err_out:
len = PAGE_CACHE_SIZE;
if (len > bytes)
len = bytes;
- zero_user_page(*pages, 0, len, KM_USER0);
+ zero_user(*pages, 0, len);
}
goto out;
}
@@ -1450,7 +1448,7 @@ err_out:
len = PAGE_CACHE_SIZE;
if (len > bytes)
len = bytes;
- zero_user_page(*pages, 0, len, KM_USER0);
+ zero_user(*pages, 0, len);
}
goto out;
}
-
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