From: NeilBrown <neilb@suse.de>
Date: Thu, 15 Jul 2010 18:44:45 +0000 (+0200)
Subject: Use write_begin/write_end in place of prepare/commit
X-Git-Url: http://git.neil.brown.name/?a=commitdiff_plain;h=68aa040d0df4a4d7ca5cde4228e172f19bffaa94;p=LaFS.git

Use write_begin/write_end in place of prepare/commit

As this is the 'new way' and need for upgrading the base kernel.

Signed-off-by: NeilBrown <neilb@suse.de>
---

diff --git a/file.c b/file.c
index 4c4b36d..d88bcfe 100644
--- a/file.c
+++ b/file.c
@@ -11,6 +11,7 @@
 #include	"lafs.h"
 #include	<linux/bit_spinlock.h>
 #include	<linux/writeback.h>
+#include	<linux/version.h>
 
 struct readpage_data {
 	struct bio *bio;
@@ -115,8 +116,9 @@ lafs_readpages(struct file *file, struct address_space *mapping,
 
 
 static int
-lafs_prepare_write(struct file *file, struct page *page,
-		   unsigned start, unsigned end)
+lafs_write_begin(struct file *file, struct address_space *mapping,
+		 loff_t pos, unsigned len, unsigned flags,
+		 struct page **pagep, void **fsdata)
 {
 	/* The range covers one or more blocks in this page
 	 * and may partially cover the first or last.
@@ -125,21 +127,37 @@ lafs_prepare_write(struct file *file, struct page *page,
 	 * Then we 'reserve' those datablocks to ensure that
 	 * a write will succeed.
 	 */
-	struct inode *ino = file->f_dentry->d_inode;
+	struct inode *ino = mapping->host;
 	struct fs *fs = fs_from_inode(ino);
 	int bits = ino->i_blkbits;
 	int first, last, loading = -1;
 	struct datablock *fb;
 	int err = 0;
 	int i;
+	pgoff_t index;
+	unsigned from, to;
+	struct page *page;
 
-	first = start >> bits;
-	last = (end-1) >> bits;
+	index = pos >> PAGE_CACHE_SHIFT;
+	from = pos & (PAGE_CACHE_SIZE - 1);
+	to = from + len;
+
+	first = from >> bits;
+	last = (to-1) >> bits;
 
 	wait_event(fs->trunc_wait,
 		   !test_bit(I_Trunc, &LAFSI(ino)->iflags) ||
 		   LAFSI(ino)->trunc_next > last);
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,29)
+	page = __grab_cache_page(mapping, index);
+#else
+	page = grab_cache_page_write_begin(mapping, index, flags);
+#endif
+	if (!page)
+		return -ENOMEM;
+	*pagep = page;
+
 	fb = lafs_get_block(ino, first, page, GFP_KERNEL, MKREF(write));
 	dprintk("PREPARE %p\n", fb);
 	if (!fb)
@@ -150,7 +168,7 @@ lafs_prepare_write(struct file *file, struct page *page,
 	for (i = first + 1 ; i <= last ; i++)
 		lafs_get_block(ino, i, page, GFP_KERNEL, MKREF(write));
 
-	if (start != (first << bits)) {
+	if (from != (first << bits)) {
 		err = lafs_find_block(fb, NOADOPT);
 		if (!err)
 			err = lafs_load_block(&fb->b, NULL);
@@ -159,7 +177,7 @@ lafs_prepare_write(struct file *file, struct page *page,
 		loading = first;
 	}
 	if (last != loading &&
-	    end != ((last+1) << bits)) {
+	    to != ((last+1) << bits)) {
 		struct datablock *lb = fb + last - first;
 
 		err = lafs_find_block(lb, ADOPT);
@@ -191,6 +209,7 @@ retry:
 	}
 	if (err < 0)
 		goto fail;
+	*fsdata = fb;
 	return 0;
 
 fail:
@@ -201,22 +220,33 @@ fail:
 }
 
 static int
-lafs_commit_write(struct file *file, struct page *page,
-		  unsigned start, unsigned end)
+lafs_write_end(struct file *file,
+	       struct address_space *mapping,
+	       loff_t pos, unsigned len, unsigned copied,
+	       struct page *page, void *fsdata)
 {
-	struct inode *ino = file->f_dentry->d_inode;
+	struct inode *ino = mapping->host;
 	struct fs *fs = fs_from_inode(ino);
 	int bits = ino->i_blkbits;
-	int first, last;
+	unsigned first, last;
 	struct datablock *fb;
-	int i;
-	loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + end;
+	unsigned i;
+	pgoff_t index;
+	unsigned from, to;
+
+	index = pos >> PAGE_CACHE_SHIFT;
+	from = pos & (PAGE_CACHE_SIZE - 1);
+	to = from + len;
 
-	first = start >> bits;
-	last = (end-1) >> bits;
+	first = from >> bits;
+	last = (to-1) >> bits;
 
-	fb = lafs_get_block(ino, first, page, GFP_KERNEL, MKREF(commit));
-	BUG_ON(!fb);
+	fb = fsdata;
+
+	if (unlikely(copied < len)) {
+		if (!PageUptodate(page))
+			copied = 0;
+	}
 
 	/*
 	 * No need to use i_size_read() here, the i_size
@@ -236,13 +266,16 @@ lafs_commit_write(struct file *file, struct page *page,
 	}
 	__set_page_dirty_nobuffers(page);
 	for (i = first ; i <= last ; i++) {
-		set_bit(B_Valid, &(fb+i-first)->b.flags);
-		lafs_dirty_dblock(fb+i-first);
+		if (copied > 0) {
+			set_bit(B_Valid, &(fb+i-first)->b.flags);
+			lafs_dirty_dblock(fb+i-first);
+		}
 		putdref(fb+i-first, MKREF(write));
 	}
-	putdref(fb, MKREF(commit));
 	lafs_checkpoint_unlock(fs);
-	return 0;
+	unlock_page(page);
+	page_cache_release(page);
+	return copied;
 }
 
 static int
@@ -401,8 +434,8 @@ struct address_space_operations lafs_file_aops = {
 	.readpage	= lafs_readpage,
 	.readpages	= lafs_readpages,
 	.writepage	= lafs_writepage,
-	.prepare_write	= lafs_prepare_write,
-	.commit_write	= lafs_commit_write,
+	.write_begin	= lafs_write_begin,
+	.write_end	= lafs_write_end,
 	.invalidatepage	= lafs_invalidate_page,
 	.releasepage	= lafs_release_page,
 	.sync_page	= lafs_sync_page,