On Fri, Feb 02, 2007 at 12:05:11PM +0000, Christoph Hellwig wrote:
> 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:
>
You probably need s/memclear/clearmem/g..
> 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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