[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, 135 insertions, 13 deletions

diff --git a/fs/ufs/truncate.c b/fs/ufs/truncate.c
index 3c3b301f8701..c9b55872079b 100644
--- a/fs/ufs/truncate.c
+++ b/fs/ufs/truncate.c
@@ -369,24 +369,97 @@ static int ufs_trunc_tindirect (struct inode * inode)
         UFSD("EXIT\n");
         return retry;
 }
-                
-void ufs_truncate (struct inode * inode)
+
+static int ufs_alloc_lastblock(struct inode *inode)
 {
+        int err = 0;
+        struct address_space *mapping = inode->i_mapping;
+        struct ufs_sb_private_info *uspi = UFS_SB(inode->i_sb)->s_uspi;
         struct ufs_inode_info *ufsi = UFS_I(inode);
-        struct super_block * sb;
-        struct ufs_sb_private_info * uspi;
-        int retry;
+        unsigned lastfrag, i, end;
+        struct page *lastpage;
+        struct buffer_head *bh;
+
+        lastfrag = (i_size_read(inode) + uspi->s_fsize - 1) >> uspi->s_fshift;
+
+        if (!lastfrag) {
+                ufsi->i_lastfrag = 0;
+                goto out;
+        }
+        lastfrag--;
+
+        lastpage = ufs_get_locked_page(mapping, lastfrag >>
+                                       (PAGE_CACHE_SHIFT - inode->i_blkbits));
+       if (IS_ERR(lastpage)) {
+               err = -EIO;
+               goto out;
+       }
+
+       end = lastfrag & ((1 << (PAGE_CACHE_SHIFT - inode->i_blkbits)) - 1);
+       bh = page_buffers(lastpage);
+       for (i = 0; i < end; ++i)
+               bh = bh->b_this_page;
+
+       if (!buffer_mapped(bh)) {
+               err = ufs_getfrag_block(inode, lastfrag, bh, 1);
+
+               if (unlikely(err))
+                       goto out_unlock;
+
+               if (buffer_new(bh)) {
+                       clear_buffer_new(bh);
+                       unmap_underlying_metadata(bh->b_bdev,
+                                                 bh->b_blocknr);
+                       /*
+                        * we do not zeroize fragment, because of
+                        * if it maped to hole, it already contains zeroes
+                        */
+                       set_buffer_uptodate(bh);
+                       mark_buffer_dirty(bh);
+                       set_page_dirty(lastpage);
+               }
+       }
+out_unlock:
+       ufs_put_locked_page(lastpage);
+out:
+       return err;
+}
+
+int ufs_truncate(struct inode *inode, loff_t old_i_size)
+{
+        struct ufs_inode_info *ufsi = UFS_I(inode);
+        struct super_block *sb = inode->i_sb;
+        struct ufs_sb_private_info *uspi = UFS_SB(sb)->s_uspi;
+        int retry, err = 0;
         
         UFSD("ENTER\n");
-        sb = inode->i_sb;
-        uspi = UFS_SB(sb)->s_uspi;
 
-        if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)))
-                return;
+        if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
+              S_ISLNK(inode->i_mode)))
+                return -EINVAL;
         if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
-                return;
+                return -EPERM;
+
+        if (inode->i_size > old_i_size) {
+                /*
+                 * if we expand file we should care about
+                 * allocation of block for last byte first of all
+                 */
+                err = ufs_alloc_lastblock(inode);
+
+                if (err) {
+                        i_size_write(inode, old_i_size);
+                        goto out;
+                }
+                /*
+                 * go away, because of we expand file, and we do not
+                 * need free blocks, and zeroizes page
+                 */
+                lock_kernel();
+                goto almost_end;
+        }
 
-        block_truncate_page(inode->i_mapping,   inode->i_size, ufs_getfrag_block);
+        block_truncate_page(inode->i_mapping, inode->i_size, ufs_getfrag_block);
 
         lock_kernel();
         while (1) {
@@ -404,9 +477,58 @@ void ufs_truncate (struct inode * inode)
                 yield();
         }
 
+        if (inode->i_size < old_i_size) {
+                /*
+                 * now we should have enough space
+                 * to allocate block for last byte
+                 */
+                err = ufs_alloc_lastblock(inode);
+                if (err)
+                        /*
+                         * looks like all the same - we have no space,
+                         * but we truncate file already
+                         */
+                        inode->i_size = (ufsi->i_lastfrag - 1) * uspi->s_fsize;
+        }
+almost_end:
         inode->i_mtime = inode->i_ctime = CURRENT_TIME_SEC;
-        ufsi->i_lastfrag = DIRECT_FRAGMENT;
         unlock_kernel();
         mark_inode_dirty(inode);
-        UFSD("EXIT\n");
+out:
+        UFSD("EXIT: err %d\n", err);
+        return err;
 }
+
+
+/*
+ * We don't define our `inode->i_op->truncate', and call it here,
+ * because of:
+ * - there is no way to know old size
+ * - there is no way inform user about error, if it happens in `truncate'
+ */
+static int ufs_setattr(struct dentry *dentry, struct iattr *attr)
+{
+        struct inode *inode = dentry->d_inode;
+        unsigned int ia_valid = attr->ia_valid;
+        int error;
+
+        error = inode_change_ok(inode, attr);
+        if (error)
+                return error;
+
+        if (ia_valid & ATTR_SIZE &&
+            attr->ia_size != i_size_read(inode)) {
+                loff_t old_i_size = inode->i_size;
+                error = vmtruncate(inode, attr->ia_size);
+                if (error)
+                        return error;
+                error = ufs_truncate(inode, old_i_size);
+                if (error)
+                        return error;
+        }
+        return inode_setattr(inode, attr);
+}
+
+struct inode_operations ufs_file_inode_operations = {
+        .setattr = ufs_setattr,
+};