xfs: new truncate sequence

Convert XFS to the new truncate sequence.  We still can have errors after
updating the file size in xfs_setattr, but these are real I/O errors and lead
to a transaction abort and filesystem shutdown, so they are not an issue.

Errors from ->write_begin and write_end can now be handled correctly because
we can actually get rid of the delalloc extents while previous the buffer
state was stipped in block_invalidatepage.

There is still no error handling for ->direct_IO, because doing so will need
some major restructuring given that we only have the iolock shared and do not
hold i_mutex at all.  Fortunately leaving the normally allocated blocks behind
there is not a major issue and this will get cleaned up by xfs_free_eofblock
later.

Note: the patch is against Al's vfs.git tree as that contains the nessecary
preparations.  I'd prefer to get it applied there so that we can get some
testing in linux-next.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 36 insertions, 6 deletions

diff --git a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c
index bf7aad0d78b8..15412fe15c3a 100644
--- a/fs/xfs/linux-2.6/xfs_aops.c
+++ b/fs/xfs/linux-2.6/xfs_aops.c
@@ -1494,6 +1494,22 @@ xfs_vm_direct_IO(
         return ret;
 }
 
+STATIC void
+xfs_vm_write_failed(
+        struct address_space    *mapping,
+        loff_t                  to)
+{
+        struct inode            *inode = mapping->host;
+
+        if (to > inode->i_size) {
+                struct iattr    ia = {
+                        .ia_valid       = ATTR_SIZE | ATTR_FORCE,
+                        .ia_size        = inode->i_size,
+                };
+                xfs_setattr(XFS_I(inode), &ia, XFS_ATTR_NOLOCK);
+        }
+}
+
 STATIC int
 xfs_vm_write_begin(
         struct file             *file,
@@ -1508,12 +1524,26 @@ xfs_vm_write_begin(
 
         ret = block_write_begin(mapping, pos, len, flags | AOP_FLAG_NOFS,
                                 pagep, xfs_get_blocks);
-        if (unlikely(ret)) {
-                loff_t isize = mapping->host->i_size;
-                if (pos + len > isize)
-                        vmtruncate(mapping->host, isize);
-        }
+        if (unlikely(ret))
+                xfs_vm_write_failed(mapping, pos + len);
+        return ret;
+}
+
+STATIC int
+xfs_vm_write_end(
+        struct file             *file,
+        struct address_space    *mapping,
+        loff_t                  pos,
+        unsigned                len,
+        unsigned                copied,
+        struct page             *page,
+        void                    *fsdata)
+{
+        int                     ret;
 
+        ret = generic_write_end(file, mapping, pos, len, copied, page, fsdata);
+        if (unlikely(ret < len))
+                xfs_vm_write_failed(mapping, pos + len);
         return ret;
 }
 
@@ -1559,7 +1589,7 @@ const struct address_space_operations xfs_address_space_operations = {
         .releasepage            = xfs_vm_releasepage,
         .invalidatepage         = xfs_vm_invalidatepage,
         .write_begin            = xfs_vm_write_begin,
-        .write_end              = generic_write_end,
+        .write_end              = xfs_vm_write_end,
         .bmap                   = xfs_vm_bmap,
         .direct_IO              = xfs_vm_direct_IO,
         .migratepage            = buffer_migrate_page,