Date:	Thu, 25 Sep 2008 16:01:08 +0100
From:	David Howells <dhowells@...hat.com>
To:	torvalds@...l.org, akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, Nick Piggin <npiggin@...e.de>,
	David Howells <dhowells@...hat.com>
Subject: [PATCH] AFS: Convert to new write aops

From: Nick Piggin <npiggin@...e.de>

Convert AFS to the new write address space operations.

This cannot assume that writes will fully complete, so this conversion goes the
easy way and always brings the page uptodate before the write.

Signed-off-by: Nick Piggin <npiggin@...e.de>
Signed-off-by: David Howells <dhowells@...hat.com>
---

 fs/afs/file.c     |    4 +-
 fs/afs/internal.h |    8 ++-
 fs/afs/write.c    |  131 +++++++++++++++++------------------------------------
 3 files changed, 51 insertions(+), 92 deletions(-)


diff --git a/fs/afs/file.c b/fs/afs/file.c
index 8e24e96..909083d 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -55,8 +55,8 @@ const struct address_space_operations afs_fs_aops = {
 	.launder_page	= afs_launder_page,
 	.releasepage	= afs_releasepage,
 	.invalidatepage	= afs_invalidatepage,
-	.prepare_write	= afs_prepare_write,
-	.commit_write	= afs_commit_write,
+	.write_begin	= afs_write_begin,
+	.write_end	= afs_write_end,
 	.writepage	= afs_writepage,
 	.writepages	= afs_writepages,
 };
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 979eb1d..a7f81cc 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -722,8 +722,12 @@ extern int afs_volume_release_fileserver(struct afs_vnode *,
  */
 extern int afs_set_page_dirty(struct page *);
 extern void afs_put_writeback(struct afs_writeback *);
-extern int afs_prepare_write(struct file *, struct page *, unsigned, unsigned);
-extern int afs_commit_write(struct file *, struct page *, unsigned, unsigned);
+extern int afs_write_begin(struct file *file, struct address_space *mapping,
+			loff_t pos, unsigned len, unsigned flags,
+			struct page **pagep, void **fsdata);
+extern int afs_write_end(struct file *file, struct address_space *mapping,
+			loff_t pos, unsigned len, unsigned copied,
+			struct page *page, void *fsdata);
 extern int afs_writepage(struct page *, struct writeback_control *);
 extern int afs_writepages(struct address_space *, struct writeback_control *);
 extern int afs_write_inode(struct inode *, int);
diff --git a/fs/afs/write.c b/fs/afs/write.c
index cabc466..4f5295a 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -84,15 +84,23 @@ void afs_put_writeback(struct afs_writeback *wb)
  * partly or wholly fill a page that's under preparation for writing
  */
 static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
-			 unsigned start, unsigned len, struct page *page)
+			 loff_t pos, unsigned len, struct page *page)
 {
+	loff_t i_size;
+	unsigned eof;
 	int ret;
 
-	_enter(",,%u,%u", start, len);
+	_enter(",,%llu,%u", (unsigned long long)pos, len);
 
-	ASSERTCMP(start + len, <=, PAGE_SIZE);
+	ASSERTCMP(len, <=, PAGE_CACHE_SIZE);
 
-	ret = afs_vnode_fetch_data(vnode, key, start, len, page);
+	i_size = i_size_read(&vnode->vfs_inode);
+	if (pos + len > i_size)
+		eof = i_size;
+	else
+		eof = PAGE_CACHE_SIZE;
+
+	ret = afs_vnode_fetch_data(vnode, key, 0, eof, page);
 	if (ret < 0) {
 		if (ret == -ENOENT) {
 			_debug("got NOENT from server"
@@ -107,109 +115,55 @@ static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
 }
 
 /*
- * prepare a page for being written to
- */
-static int afs_prepare_page(struct afs_vnode *vnode, struct page *page,
-			    struct key *key, unsigned offset, unsigned to)
-{
-	unsigned eof, tail, start, stop, len;
-	loff_t i_size, pos;
-	void *p;
-	int ret;
-
-	_enter("");
-
-	if (offset == 0 && to == PAGE_SIZE)
-		return 0;
-
-	p = kmap_atomic(page, KM_USER0);
-
-	i_size = i_size_read(&vnode->vfs_inode);
-	pos = (loff_t) page->index << PAGE_SHIFT;
-	if (pos >= i_size) {
-		/* partial write, page beyond EOF */
-		_debug("beyond");
-		if (offset > 0)
-			memset(p, 0, offset);
-		if (to < PAGE_SIZE)
-			memset(p + to, 0, PAGE_SIZE - to);
-		kunmap_atomic(p, KM_USER0);
-		return 0;
-	}
-
-	if (i_size - pos >= PAGE_SIZE) {
-		/* partial write, page entirely before EOF */
-		_debug("before");
-		tail = eof = PAGE_SIZE;
-	} else {
-		/* partial write, page overlaps EOF */
-		eof = i_size - pos;
-		_debug("overlap %u", eof);
-		tail = max(eof, to);
-		if (tail < PAGE_SIZE)
-			memset(p + tail, 0, PAGE_SIZE - tail);
-		if (offset > eof)
-			memset(p + eof, 0, PAGE_SIZE - eof);
-	}
-
-	kunmap_atomic(p, KM_USER0);
-
-	ret = 0;
-	if (offset > 0 || eof > to) {
-		/* need to fill one or two bits that aren't going to be written
-		 * (cover both fillers in one read if there are two) */
-		start = (offset > 0) ? 0 : to;
-		stop = (eof > to) ? eof : offset;
-		len = stop - start;
-		_debug("wr=%u-%u av=0-%u rd=%u@%u",
-		       offset, to, eof, start, len);
-		ret = afs_fill_page(vnode, key, start, len, page);
-	}
-
-	_leave(" = %d", ret);
-	return ret;
-}
-
-/*
  * prepare to perform part of a write to a page
- * - the caller holds the page locked, preventing it from being written out or
- *   modified by anyone else
  */
-int afs_prepare_write(struct file *file, struct page *page,
-		      unsigned offset, unsigned to)
+int afs_write_begin(struct file *file, struct address_space *mapping,
+		    loff_t pos, unsigned len, unsigned flags,
+		    struct page **pagep, void **fsdata)
 {
 	struct afs_writeback *candidate, *wb;
 	struct afs_vnode *vnode = AFS_FS_I(file->f_dentry->d_inode);
+	struct page *page;
 	struct key *key = file->private_data;
-	pgoff_t index;
+	unsigned from = pos & (PAGE_CACHE_SIZE - 1);
+	unsigned to = from + len;
+	pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 	int ret;
 
 	_enter("{%x:%u},{%lx},%u,%u",
-	       vnode->fid.vid, vnode->fid.vnode, page->index, offset, to);
+	       vnode->fid.vid, vnode->fid.vnode, index, from, to);
 
 	candidate = kzalloc(sizeof(*candidate), GFP_KERNEL);
 	if (!candidate)
 		return -ENOMEM;
 	candidate->vnode = vnode;
-	candidate->first = candidate->last = page->index;
-	candidate->offset_first = offset;
+	candidate->first = candidate->last = index;
+	candidate->offset_first = from;
 	candidate->to_last = to;
 	candidate->usage = 1;
 	candidate->state = AFS_WBACK_PENDING;
 	init_waitqueue_head(&candidate->waitq);
 
+	page = __grab_cache_page(mapping, index);
+	if (!page) {
+		kfree(candidate);
+		return -ENOMEM;
+	}
+	*pagep = page;
+	/* page won't leak in error case: it eventually gets cleaned off LRU */
+
 	if (!PageUptodate(page)) {
 		_debug("not up to date");
-		ret = afs_prepare_page(vnode, page, key, offset, to);
+		ret = afs_fill_page(vnode, key, pos, len, page);
 		if (ret < 0) {
 			kfree(candidate);
 			_leave(" = %d [prep]", ret);
 			return ret;
 		}
+		SetPageUptodate(page);
 	}
 
 try_again:
-	index = page->index;
 	spin_lock(&vnode->writeback_lock);
 
 	/* see if this page is already pending a writeback under a suitable key
@@ -242,8 +196,8 @@ try_again:
 subsume_in_current_wb:
 	_debug("subsume");
 	ASSERTRANGE(wb->first, <=, index, <=, wb->last);
-	if (index == wb->first && offset < wb->offset_first)
-		wb->offset_first = offset;
+	if (index == wb->first && from < wb->offset_first)
+		wb->offset_first = from;
 	if (index == wb->last && to > wb->to_last)
 		wb->to_last = to;
 	spin_unlock(&vnode->writeback_lock);
@@ -289,17 +243,17 @@ flush_conflicting_wb:
 /*
  * finalise part of a write to a page
  */
-int afs_commit_write(struct file *file, struct page *page,
-		     unsigned offset, unsigned to)
+int afs_write_end(struct file *file, struct address_space *mapping,
+		  loff_t pos, unsigned len, unsigned copied,
+		  struct page *page, void *fsdata)
 {
 	struct afs_vnode *vnode = AFS_FS_I(file->f_dentry->d_inode);
 	loff_t i_size, maybe_i_size;
 
-	_enter("{%x:%u},{%lx},%u,%u",
-	       vnode->fid.vid, vnode->fid.vnode, page->index, offset, to);
+	_enter("{%x:%u},{%lx}",
+	       vnode->fid.vid, vnode->fid.vnode, page->index);
 
-	maybe_i_size = (loff_t) page->index << PAGE_SHIFT;
-	maybe_i_size += to;
+	maybe_i_size = pos + copied;
 
 	i_size = i_size_read(&vnode->vfs_inode);
 	if (maybe_i_size > i_size) {
@@ -310,12 +264,13 @@ int afs_commit_write(struct file *file, struct page *page,
 		spin_unlock(&vnode->writeback_lock);
 	}
 
-	SetPageUptodate(page);
 	set_page_dirty(page);
 	if (PageDirty(page))
 		_debug("dirtied");
+	unlock_page(page);
+	page_cache_release(page);
 
-	return 0;
+	return copied;
 }
 
 /*

--
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