[PATCH] ufs: change block number on the fly

[Evgeniy Dushistov]

This patch should fix current implementation of
"changing block numbers" to avoid kernel hangup,
data corruption and so on.

Signed-off-by: Evgeniy Dushistov <dushistov@xxxxxxx>

---

diff -upr -X linux-2.6.17-rc4/Documentation/dontdiff linux-2.6.17-rc4-vanilla/fs/ufs/balloc.c linux-2.6.17-rc4/fs/ufs/balloc.c
--- linux-2.6.17-rc4-vanilla/fs/ufs/balloc.c	2006-05-17 11:46:45.147277000 +0400
+++ linux-2.6.17-rc4/fs/ufs/balloc.c	2006-05-17 10:14:55.554375500 +0400
@@ -39,7 +39,8 @@ static void ufs_clusteracct(struct super
 /*
  * Free 'count' fragments from fragment number 'fragment'
  */
-void ufs_free_fragments (struct inode * inode, unsigned fragment, unsigned count) {
+void ufs_free_fragments (struct inode * inode, unsigned fragment, unsigned count)
+{
 	struct super_block * sb;
 	struct ufs_sb_private_info * uspi;
 	struct ufs_super_block_first * usb1;
@@ -134,7 +135,8 @@ failed:
 /*
  * Free 'count' fragments from fragment number 'fragment' (free whole blocks)
  */
-void ufs_free_blocks (struct inode * inode, unsigned fragment, unsigned count) {
+void ufs_free_blocks (struct inode * inode, unsigned fragment, unsigned count)
+{
 	struct super_block * sb;
 	struct ufs_sb_private_info * uspi;
 	struct ufs_super_block_first * usb1;
@@ -222,15 +224,115 @@ failed:
 	return;
 }
 
+static struct page * ufs_get_locked_page(struct address_space *mapping, 
+				  unsigned long index)
+{
+	struct page *page;
+try_again:
+	page = find_lock_page(mapping, index);
+	if (!page) {
+		page = read_cache_page(mapping, index,
+				       (filler_t*)mapping->a_ops->readpage, 
+				       NULL);
+		if (IS_ERR(page)) {
+			printk(KERN_ERR "ufs_change_blocknr: "
+			       "read_cache_page error: ino %lu, index: %lu\n",
+			       mapping->host->i_ino, index);
+			goto out;
+		}
+
+		lock_page(page);
+			
+		if (!PageUptodate(page) || PageError(page)) {
+			unlock_page(page);
+			page_cache_release(page);
+
+			printk(KERN_ERR "ufs_change_blocknr: "
+			       "can not read page: ino %lu, index: %lu\n",
+			       mapping->host->i_ino, index);
+
+			page = ERR_PTR(-EIO);
+			goto out;
+		}
+	}
+
+	if (unlikely(!page_has_buffers(page))) {
+		unlock_page(page);
+		page_cache_release(page);
+		goto try_again;/*we really need these buffers*/
+	}
+out:
+	return page;
+}
+
+/*
+ * Modify inode page cache in such way:
+ * have - blocks with b_blocknr equal to oldb...oldb+count-1
+ * get - blocks with b_blocknr equal to newb...newb+count-1
+ * also we suppose that oldb...oldb+count-1 blocks 
+ * situated at the end of file.
+ *
+ * We can come here from ufs_writepage or ufs_prepare_write,
+ * locked_page is argument of these functions, so we already lock it.
+ */
+static void ufs_change_blocknr(struct inode *inode, unsigned int count, 
+			       unsigned int oldb, unsigned int newb, 
+			       struct page *locked_page)
+{
+	unsigned int blk_per_page = 1UL << (PAGE_CACHE_SHIFT - inode->i_blkbits);
+	sector_t baseblk = ((inode->i_size-1)>>inode->i_blkbits) + 1 - count;
+	struct address_space *mapping = inode->i_mapping;
+	pgoff_t index, cur_index = locked_page->index;
+	unsigned int i, j;
+	struct page *page;
+	struct buffer_head *head, *bh;
+
+	UFSD(("ENTER, ino %lu, count %u, oldb %u, newb %u\n",
+	      inode->i_ino, count, oldb, newb));
+      
+	BUG_ON(!PageLocked(locked_page));
+
+	for (i = 0; i < count; i += blk_per_page) {
+		index = (baseblk+i) >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
+
+		if (likely(cur_index != index)) {
+			page = ufs_get_locked_page(mapping, index);
+			if (IS_ERR(page))
+				continue;			
+		} else
+			page = locked_page;
+
+		j = i;
+		head = page_buffers(page);
+		bh = head;
+		do {
+			if (likely(bh->b_blocknr == j + oldb && j < count)) {
+				unmap_underlying_metadata(bh->b_bdev,
+							  bh->b_blocknr);
+				bh->b_blocknr = newb + j++;
+				mark_buffer_dirty(bh);
+			}
+ 
+			bh = bh->b_this_page;
+		} while (bh != head);
+ 
+		set_page_dirty(page);
+
+		if (likely(cur_index != index)) {
+			unlock_page(page);
+			page_cache_release(page);
+		}
+ 	}
+	UFSD(("EXIT\n"));
+}
 
-unsigned ufs_new_fragments (struct inode * inode, __fs32 * p, unsigned fragment,
-	unsigned goal, unsigned count, int * err )
+unsigned ufs_new_fragments(struct inode * inode, __fs32 * p, unsigned fragment,
+			   unsigned goal, unsigned count, int * err, struct page *locked_page)
 {
 	struct super_block * sb;
 	struct ufs_sb_private_info * uspi;
 	struct ufs_super_block_first * usb1;
-	struct buffer_head * bh;
-	unsigned cgno, oldcount, newcount, tmp, request, i, result;
+	unsigned cgno, oldcount, newcount, tmp, request, result;
 	
 	UFSD(("ENTER, ino %lu, fragment %u, goal %u, count %u\n", inode->i_ino, fragment, goal, count))
 	
@@ -343,24 +445,8 @@ unsigned ufs_new_fragments (struct inode
 	}
 	result = ufs_alloc_fragments (inode, cgno, goal, request, err);
 	if (result) {
-		for (i = 0; i < oldcount; i++) {
-			bh = sb_bread(sb, tmp + i);
-			if(bh)
-			{
-				clear_buffer_dirty(bh);
-				bh->b_blocknr = result + i;
-				mark_buffer_dirty (bh);
-				if (IS_SYNC(inode))
-					sync_dirty_buffer(bh);
-				brelse (bh);
-			}
-			else
-			{
-				printk(KERN_ERR "ufs_new_fragments: bread fail\n");
-				unlock_super(sb);
-				return 0;
-			}
-		}
+		ufs_change_blocknr(inode, oldcount, tmp, result, locked_page);
+
 		*p = cpu_to_fs32(sb, result);
 		*err = 0;
 		inode->i_blocks += count << uspi->s_nspfshift;
diff -upr -X linux-2.6.17-rc4/Documentation/dontdiff linux-2.6.17-rc4-vanilla/fs/ufs/inode.c linux-2.6.17-rc4/fs/ufs/inode.c
--- linux-2.6.17-rc4-vanilla/fs/ufs/inode.c	2006-05-17 11:46:45.167278250 +0400
+++ linux-2.6.17-rc4/fs/ufs/inode.c	2006-05-16 13:36:27.447118250 +0400
@@ -173,9 +173,10 @@ static inline void ufs_clear_block(struc
 }
 
 
-static struct buffer_head * ufs_inode_getfrag (struct inode *inode,
-	unsigned int fragment, unsigned int new_fragment,
-	unsigned int required, int *err, int metadata, long *phys, int *new)
+static struct buffer_head *ufs_inode_getfrag(struct inode *inode,
+					     unsigned int fragment, unsigned int new_fragment,
+					     unsigned int required, int *err, int metadata, 
+					     long *phys, int *new, struct page *locked_page)
 {
 	struct ufs_inode_info *ufsi = UFS_I(inode);
 	struct super_block * sb;
@@ -233,7 +234,8 @@ repeat:
 		if (lastblockoff) {
 			p2 = ufsi->i_u1.i_data + lastblock;
 			tmp = ufs_new_fragments (inode, p2, lastfrag, 
-				fs32_to_cpu(sb, *p2), uspi->s_fpb - lastblockoff, err);
+						 fs32_to_cpu(sb, *p2), uspi->s_fpb - lastblockoff, 
+						 err, locked_page);
 			if (!tmp) {
 				if (lastfrag != ufsi->i_lastfrag)
 					goto repeat;
@@ -245,14 +247,16 @@ repeat:
 		}
 		goal = fs32_to_cpu(sb, ufsi->i_u1.i_data[lastblock]) + uspi->s_fpb;
 		tmp = ufs_new_fragments (inode, p, fragment - blockoff, 
-			goal, required + blockoff, err);
+					 goal, required + blockoff, 
+					 err, locked_page);
 	}
 	/*
 	 * We will extend last allocated block
 	 */
 	else if (lastblock == block) {
-		tmp = ufs_new_fragments (inode, p, fragment - (blockoff - lastblockoff),
-			fs32_to_cpu(sb, *p), required +  (blockoff - lastblockoff), err);
+		tmp = ufs_new_fragments(inode, p, fragment - (blockoff - lastblockoff),
+					fs32_to_cpu(sb, *p), required +  (blockoff - lastblockoff), 
+					err, locked_page);
 	}
 	/*
 	 * We will allocate new block before last allocated block
@@ -260,8 +264,8 @@ repeat:
 	else /* (lastblock > block) */ {
 		if (lastblock && (tmp = fs32_to_cpu(sb, ufsi->i_u1.i_data[lastblock-1])))
 			goal = tmp + uspi->s_fpb;
-		tmp = ufs_new_fragments (inode, p, fragment - blockoff, 
-			goal, uspi->s_fpb, err);
+		tmp = ufs_new_fragments(inode, p, fragment - blockoff, 
+					goal, uspi->s_fpb, err, locked_page);
 	}
 	if (!tmp) {
 		if ((!blockoff && *p) || 
@@ -304,9 +308,10 @@ repeat2:
      */
 }
 
-static struct buffer_head * ufs_block_getfrag (struct inode *inode,
-	struct buffer_head *bh, unsigned int fragment, unsigned int new_fragment, 
-	unsigned int blocksize, int * err, int metadata, long *phys, int *new)
+static struct buffer_head *ufs_block_getfrag(struct inode *inode, struct buffer_head *bh, 
+					     unsigned int fragment, unsigned int new_fragment, 
+					     unsigned int blocksize, int * err, int metadata, 
+					     long *phys, int *new, struct page *locked_page)
 {
 	struct super_block * sb;
 	struct ufs_sb_private_info * uspi;
@@ -351,7 +356,8 @@ repeat:
 		goal = tmp + uspi->s_fpb;
 	else
 		goal = bh->b_blocknr + uspi->s_fpb;
-	tmp = ufs_new_fragments (inode, p, ufs_blknum(new_fragment), goal, uspi->s_fpb, err);
+	tmp = ufs_new_fragments(inode, p, ufs_blknum(new_fragment), goal, 
+				uspi->s_fpb, err, locked_page);
 	if (!tmp) {
 		if (fs32_to_cpu(sb, *p))
 			goto repeat;
@@ -425,15 +431,15 @@ int ufs_getfrag_block (struct inode *ino
 	 * it much more readable:
 	 */
 #define GET_INODE_DATABLOCK(x) \
-		ufs_inode_getfrag(inode, x, fragment, 1, &err, 0, &phys, &new)
+	ufs_inode_getfrag(inode, x, fragment, 1, &err, 0, &phys, &new, bh_result->b_page)
 #define GET_INODE_PTR(x) \
-		ufs_inode_getfrag(inode, x, fragment, uspi->s_fpb, &err, 1, NULL, NULL)
+	ufs_inode_getfrag(inode, x, fragment, uspi->s_fpb, &err, 1, NULL, NULL, bh_result->b_page)
 #define GET_INDIRECT_DATABLOCK(x) \
-		ufs_block_getfrag(inode, bh, x, fragment, sb->s_blocksize, \
-				  &err, 0, &phys, &new);
+	ufs_block_getfrag(inode, bh, x, fragment, sb->s_blocksize,	\
+			  &err, 0, &phys, &new, bh_result->b_page);
 #define GET_INDIRECT_PTR(x) \
-		ufs_block_getfrag(inode, bh, x, fragment, sb->s_blocksize, \
-				  &err, 1, NULL, NULL);
+	ufs_block_getfrag(inode, bh, x, fragment, sb->s_blocksize,	\
+			  &err, 1, NULL, NULL, bh_result->b_page);
 
 	if (ptr < UFS_NDIR_FRAGMENT) {
 		bh = GET_INODE_DATABLOCK(ptr);
diff -upr -X linux-2.6.17-rc4/Documentation/dontdiff linux-2.6.17-rc4-vanilla/include/linux/ufs_fs.h linux-2.6.17-rc4/include/linux/ufs_fs.h
--- linux-2.6.17-rc4-vanilla/include/linux/ufs_fs.h	2006-05-17 11:35:17.868324750 +0400
+++ linux-2.6.17-rc4/include/linux/ufs_fs.h	2006-05-16 13:36:27.447118250 +0400
@@ -876,7 +876,8 @@ struct ufs_super_block_third {
 /* balloc.c */
 extern void ufs_free_fragments (struct inode *, unsigned, unsigned);
 extern void ufs_free_blocks (struct inode *, unsigned, unsigned);
-extern unsigned ufs_new_fragments (struct inode *, __fs32 *, unsigned, unsigned, unsigned, int *);
+extern unsigned ufs_new_fragments(struct inode *, __fs32 *, unsigned, unsigned, 
+				  unsigned, int *, struct page *);
 
 /* cylinder.c */
 extern struct ufs_cg_private_info * ufs_load_cylinder (struct super_block *, unsigned);

-- 
/Evgeniy

-
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