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.

Compile tested in x86_64.

signed-off-by: Nate Diller <[EMAIL PROTECTED]>

---

 drivers/block/loop.c                     |    6 ---
 fs/affs/file.c                           |    6 ---
 fs/buffer.c                              |   53 +++++--------------------------
 fs/direct-io.c                           |    8 +---
 fs/ecryptfs/mmap.c                       |   14 +-------
 fs/ext3/inode.c                          |   12 +------
 fs/ext4/inode.c                          |   12 +------
 fs/ext4/writeback.c                      |   12 +------
 fs/gfs2/bmap.c                           |    6 ---
 fs/mpage.c                               |   11 +-----
 fs/nfs/read.c                            |   10 ++---
 fs/nfs/write.c                           |    2 -
 fs/ntfs/aops.c                           |   26 ++-------------
 fs/ntfs/file.c                           |   47 +++++----------------------
 fs/ocfs2/aops.c                          |    5 --
 fs/reiser4/plugin/file/cryptcompress.c   |   19 +----------
 fs/reiser4/plugin/file/file.c            |    6 ---
 fs/reiser4/plugin/item/ctail.c           |    6 ---
 fs/reiser4/plugin/item/extent_file_ops.c |   19 +++--------
 fs/reiser4/plugin/item/tail.c            |    8 +---
 fs/reiserfs/file.c                       |   39 ++++++----------------
 fs/reiserfs/inode.c                      |   13 +------
 fs/xfs/linux-2.6/xfs_lrw.c               |    2 -
 include/linux/highmem.h                  |    7 +++-
 mm/filemap_xip.c                         |    7 ----
 mm/truncate.c                            |    2 -
 26 files changed, 82 insertions(+), 276 deletions(-)

---

diff -urpN -X dontdiff linux-2.6.21-rc6-mm1/drivers/block/loop.c 
linux-2.6.21-rc6-mm1-test/drivers/block/loop.c
--- linux-2.6.21-rc6-mm1/drivers/block/loop.c   2007-04-10 18:27:04.000000000 
-0700
+++ linux-2.6.21-rc6-mm1-test/drivers/block/loop.c      2007-04-10 
18:18:16.000000000 -0700
@@ -244,17 +244,13 @@ static int do_lo_send_aops(struct loop_d
                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);
                }
                flush_dcache_page(page);
                ret = aops->commit_write(file, page, offset,
diff -urpN -X dontdiff linux-2.6.21-rc6-mm1/fs/buffer.c 
linux-2.6.21-rc6-mm1-test/fs/buffer.c
--- linux-2.6.21-rc6-mm1/fs/buffer.c    2007-04-10 18:27:04.000000000 -0700
+++ linux-2.6.21-rc6-mm1-test/fs/buffer.c       2007-04-10 18:18:16.000000000 
-0700
@@ -1862,13 +1862,8 @@ static int __block_prepare_write(struct 
                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);
                        set_buffer_uptodate(bh);
                        mark_buffer_dirty(bh);
                }
@@ -1956,10 +1951,7 @@ int block_read_full_page(struct page *pa
                                        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);
                                if (!err)
                                        set_buffer_uptodate(bh);
                                continue;
@@ -2102,7 +2094,6 @@ int cont_prepare_write(struct page *page
        long status;
        unsigned zerofrom;
        unsigned blocksize = 1 << inode->i_blkbits;
-       void *kaddr;
 
        while(page->index > (pgpos = *bytes>>PAGE_CACHE_SHIFT)) {
                status = -ENOMEM;
@@ -2124,10 +2115,7 @@ int cont_prepare_write(struct page *page
                                                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);
                generic_commit_write(NULL, new_page, zerofrom, PAGE_CACHE_SIZE);
                unlock_page(new_page);
                page_cache_release(new_page);
@@ -2154,10 +2142,7 @@ int cont_prepare_write(struct page *page
        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);
                __block_commit_write(inode, page, zerofrom, offset);
        }
        return 0;
@@ -2356,10 +2341,7 @@ failed:
         * Error recovery is pretty slack.  Clear the page and mark it dirty
         * so we'll later zero out any blocks which _were_ allocated.
         */
-       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);
        SetPageUptodate(page);
        set_page_dirty(page);
        return ret;
@@ -2398,7 +2380,6 @@ int nobh_writepage(struct page *page, ge
        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? */
@@ -2429,10 +2410,7 @@ 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."
         */
-       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);
 out:
        ret = mpage_writepage(page, get_block, wbc);
        if (ret == -EAGAIN)
@@ -2453,7 +2431,6 @@ int nobh_truncate_page(struct address_sp
        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)
@@ -2467,10 +2444,7 @@ int nobh_truncate_page(struct address_sp
        to = (offset + blocksize) & ~(blocksize - 1);
        ret = a_ops->prepare_write(NULL, page, offset, to);
        if (ret == 0) {
-               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);
                /*
                 * It would be more correct to call aops->commit_write()
                 * here, but this is more efficient.
@@ -2496,7 +2470,6 @@ int block_truncate_page(struct address_s
        struct inode *inode = mapping->host;
        struct page *page;
        struct buffer_head *bh;
-       void *kaddr;
        int err;
 
        blocksize = 1 << inode->i_blkbits;
@@ -2550,11 +2523,7 @@ int block_truncate_page(struct address_s
                        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);
        mark_buffer_dirty(bh);
        err = 0;
 
@@ -2575,7 +2544,6 @@ int block_write_full_page(struct page *p
        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)
@@ -2601,10 +2569,7 @@ 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."
         */
-       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);
        return __block_write_full_page(inode, page, get_block, wbc);
 }
 
diff -urpN -X dontdiff linux-2.6.21-rc6-mm1/fs/direct-io.c 
linux-2.6.21-rc6-mm1-test/fs/direct-io.c
--- linux-2.6.21-rc6-mm1/fs/direct-io.c 2007-04-10 18:27:04.000000000 -0700
+++ linux-2.6.21-rc6-mm1-test/fs/direct-io.c    2007-04-10 18:18:16.000000000 
-0700
@@ -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 @@ do_holes:
                                        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);
                                dio->block_in_file++;
                                block_in_page++;
                                goto next_block;
diff -urpN -X dontdiff linux-2.6.21-rc6-mm1/fs/mpage.c 
linux-2.6.21-rc6-mm1-test/fs/mpage.c
--- linux-2.6.21-rc6-mm1/fs/mpage.c     2007-04-10 18:27:04.000000000 -0700
+++ linux-2.6.21-rc6-mm1-test/fs/mpage.c        2007-04-10 18:18:16.000000000 
-0700
@@ -284,11 +284,8 @@ do_mpage_readpage(struct bio *bio, struc
        }
 
        if (first_hole != blocks_per_page) {
-               char *kaddr = kmap_atomic(page, KM_USER0);
-               memset(kaddr + (first_hole << blkbits), 0,
+               zero_user_page(page, first_hole << blkbits,
                                PAGE_CACHE_SIZE - (first_hole << blkbits));
-               flush_dcache_page(page);
-               kunmap_atomic(kaddr, KM_USER0);
                if (first_hole == 0) {
                        SetPageUptodate(page);
                        unlock_page(page);
@@ -586,14 +583,10 @@ page_is_mapped:
                 * 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);
        }
 
        /*
diff -urpN -X dontdiff linux-2.6.21-rc6-mm1/include/linux/highmem.h 
linux-2.6.21-rc6-mm1-test/include/linux/highmem.h
--- linux-2.6.21-rc6-mm1/include/linux/highmem.h        2007-04-10 
17:15:04.000000000 -0700
+++ linux-2.6.21-rc6-mm1-test/include/linux/highmem.h   2007-04-10 
18:20:11.000000000 -0700
@@ -137,7 +137,7 @@ static inline void clear_highpage(struct
 /*
  * Same but also flushes aliased cache contents to RAM.
  */
-static inline void memclear_highpage_flush(struct page *page, unsigned int 
offset, unsigned int size)
+static inline void zero_user_page(struct page *page, unsigned int offset, 
unsigned int size)
 {
        void *kaddr;
 
@@ -149,6 +149,11 @@ static inline void memclear_highpage_flu
        kunmap_atomic(kaddr, KM_USER0);
 }
 
+static inline void memclear_highpage_flush(struct page *page, unsigned int 
offset, unsigned int size)
+{
+       return zero_user_page(page, offset, size);
+}
+
 #ifndef __HAVE_ARCH_COPY_USER_HIGHPAGE
 
 static inline void copy_user_highpage(struct page *to, struct page *from,
diff -urpN -X dontdiff linux-2.6.21-rc6-mm1/mm/filemap_xip.c 
linux-2.6.21-rc6-mm1-test/mm/filemap_xip.c
--- linux-2.6.21-rc6-mm1/mm/filemap_xip.c       2007-04-10 18:27:04.000000000 
-0700
+++ linux-2.6.21-rc6-mm1-test/mm/filemap_xip.c  2007-04-10 18:18:16.000000000 
-0700
@@ -440,7 +440,6 @@ xip_truncate_page(struct address_space *
        unsigned blocksize;
        unsigned length;
        struct page *page;
-       void *kaddr;
 
        BUG_ON(!mapping->a_ops->get_xip_page);
 
@@ -464,11 +463,7 @@ xip_truncate_page(struct address_space *
                else
                        return PTR_ERR(page);
        }
-       kaddr = kmap_atomic(page, KM_USER0);
-       memset(kaddr + offset, 0, length);
-       kunmap_atomic(kaddr, KM_USER0);
-
-       flush_dcache_page(page);
+       zero_user_page(page, offset, length);
        return 0;
 }
 EXPORT_SYMBOL_GPL(xip_truncate_page);
diff -urpN -X dontdiff linux-2.6.21-rc6-mm1/mm/truncate.c 
linux-2.6.21-rc6-mm1-test/mm/truncate.c
--- linux-2.6.21-rc6-mm1/mm/truncate.c  2007-04-10 18:27:04.000000000 -0700
+++ linux-2.6.21-rc6-mm1-test/mm/truncate.c     2007-04-10 18:18:16.000000000 
-0700
@@ -46,7 +46,7 @@ void do_invalidatepage(struct page *page
 
 static inline void truncate_partial_page(struct page *page, unsigned partial)
 {
-       memclear_highpage_flush(page, partial, PAGE_CACHE_SIZE-partial);
+       zero_user_page(page, partial, PAGE_CACHE_SIZE-partial);
        if (PagePrivate(page))
                do_invalidatepage(page, partial);
 }
-
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