[PATCH] ufs: truncate should allocate block for last byte

This patch fixes buggy behaviour of UFS
in such kind of scenario:
open(, O_TRUNC...)
ftruncate(, 1024)
ftruncate(, 0)

Such a scenario causes ufs_panic and remount read-only.  This happen
because of according to specification UFS should always allocate block for
last byte, and many parts of our implementation rely on this, but
`ufs_truncate' doesn't care about this.

To make possible return error code and to know about old size, this patch
removes `truncate' from ufs inode_operations and uses `setattr' method to
call ufs_truncate.

Signed-off-by: Evgeniy Dushistov <dushistov@mail.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 54 insertions, 0 deletions

diff --git a/fs/ufs/util.c b/fs/ufs/util.c
index a2f13f45708b..337cf2c46d10 100644
--- a/fs/ufs/util.c
+++ b/fs/ufs/util.c
@@ -233,3 +233,57 @@ ufs_set_inode_dev(struct super_block *sb, struct ufs_inode_info *ufsi, dev_t dev
         else
                 ufsi->i_u1.i_data[0] = fs32;
 }
+
+/**
+ * ufs_get_locked_page() - locate, pin and lock a pagecache page, if not exist
+ * read it from disk.
+ * @mapping: the address_space to search
+ * @index: the page index
+ *
+ * Locates the desired pagecache page, if not exist we'll read it,
+ * locks it, increments its reference
+ * count and returns its address.
+ *
+ */
+
+struct page *ufs_get_locked_page(struct address_space *mapping,
+                                 pgoff_t 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->mapping || !page_has_buffers(page))) {
+                unlock_page(page);
+                page_cache_release(page);
+                goto try_again;/*we really need these buffers*/
+        }
+out:
+        return page;
+}