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Date: Fri, 2 Feb 2007 12:05:11 +0000
From: Christoph Hellwig <hch@...radead.org>
To: David Chinner <dgc@....com>
Cc: Andrew Morton <akpm@...l.org>,
"Martin J. Bligh" <mbligh@...igh.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] mm: remove global locks from mm/highmem.c
On Wed, Jan 31, 2007 at 02:22:24PM +1100, David Chinner wrote:
> > Yup. Even better, use clear_highpage().
>
> For even more goodness, clearmem_highpage_flush() does exactly
> the right thing for partial page zeroing ;)
Note that there are tons of places in buffer.c that could use
clearmem_highpage_flush(). See the so far untested patch below:
Index: linux-2.6/fs/buffer.c
===================================================================
--- linux-2.6.orig/fs/buffer.c 2007-02-02 12:53:51.000000000 +0100
+++ linux-2.6/fs/buffer.c 2007-02-02 12:59:42.000000000 +0100
@@ -1858,13 +1858,8 @@
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);
+ memclear_highpage_flush(page, block_start, bh->b_size);
set_buffer_uptodate(bh);
mark_buffer_dirty(bh);
}
@@ -1952,10 +1947,8 @@
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);
+ memclear_highpage_flush(page, i * blocksize,
+ blocksize);
if (!err)
set_buffer_uptodate(bh);
continue;
@@ -2098,7 +2091,6 @@
long status;
unsigned zerofrom;
unsigned blocksize = 1 << inode->i_blkbits;
- void *kaddr;
while(page->index > (pgpos = *bytes>>PAGE_CACHE_SHIFT)) {
status = -ENOMEM;
@@ -2120,10 +2112,8 @@
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);
+ memclear_highpage_flush(page, zerofrom,
+ PAGE_CACHE_SIZE - zerofrom);
generic_commit_write(NULL, new_page, zerofrom, PAGE_CACHE_SIZE);
unlock_page(new_page);
page_cache_release(new_page);
@@ -2150,10 +2140,7 @@
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);
+ memclear_highpage_flush(page, zerofrom, offset - zerofrom);
__block_commit_write(inode, page, zerofrom, offset);
}
return 0;
@@ -2368,10 +2355,7 @@
* 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);
+ memclear_highpage_flush(page, 0, PAGE_CACHE_SIZE);
SetPageUptodate(page);
set_page_dirty(page);
return ret;
@@ -2405,7 +2389,6 @@
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? */
@@ -2436,10 +2419,7 @@
* 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);
+ memclear_highpage_flush(page, offset, PAGE_CACHE_SIZE - offset);
out:
ret = mpage_writepage(page, get_block, wbc);
if (ret == -EAGAIN)
@@ -2460,7 +2440,6 @@
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)
@@ -2474,10 +2453,7 @@
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);
+ memclear_highpage_flush(page, offset, PAGE_CACHE_SIZE - offset);
set_page_dirty(page);
}
unlock_page(page);
@@ -2498,7 +2474,6 @@
struct inode *inode = mapping->host;
struct page *page;
struct buffer_head *bh;
- void *kaddr;
int err;
blocksize = 1 << inode->i_blkbits;
@@ -2552,11 +2527,7 @@
goto unlock;
}
- kaddr = kmap_atomic(page, KM_USER0);
- memset(kaddr + offset, 0, length);
- flush_dcache_page(page);
- kunmap_atomic(kaddr, KM_USER0);
-
+ memclear_highpage_flush(page, offset, length);
mark_buffer_dirty(bh);
err = 0;
@@ -2577,7 +2548,6 @@
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)
@@ -2603,10 +2573,7 @@
* 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);
+ memclear_highpage_flush(page, offset, PAGE_CACHE_SIZE - offset);
return __block_write_full_page(inode, page, get_block, wbc);
}
-
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