cachefiles: Implement cookie resize for truncate

Implement resizing an object, using truncate and/or fallocate to adjust the
object.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819646631.215744.13819016478175576761.stgit@warthog.procyon.org.uk/
Link: https://lore.kernel.org/r/163906952877.143852.4140962906331914859.stgit@warthog.procyon.org.uk/
Link: https://lore.kernel.org/r/163967162168.1823006.5941985259926902274.stgit@warthog.procyon.org.uk/
Link: https://lore.kernel.org/r/164021560394.640689.9972155785508094960.stgit@warthog.procyon.org.uk/

diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index ad9d311413ff44f7ef2d4d57648b7b5ffc990d4a..51c968cd00a6746363f6047ffd94c22d32c5abd9 100644 (file)
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -220,6 +220,83 @@ fail:
        return false;
 }
 
+/*
+ * Shorten the backing object to discard any dirty data and free up
+ * any unused granules.
+ */
+static bool cachefiles_shorten_object(struct cachefiles_object *object,
+                                     struct file *file, loff_t new_size)
+{
+       struct cachefiles_cache *cache = object->volume->cache;
+       struct inode *inode = file_inode(file);
+       loff_t i_size, dio_size;
+       int ret;
+
+       dio_size = round_up(new_size, CACHEFILES_DIO_BLOCK_SIZE);
+       i_size = i_size_read(inode);
+
+       trace_cachefiles_trunc(object, inode, i_size, dio_size,
+                              cachefiles_trunc_shrink);
+       ret = cachefiles_inject_remove_error();
+       if (ret == 0)
+               ret = vfs_truncate(&file->f_path, dio_size);
+       if (ret < 0) {
+               trace_cachefiles_io_error(object, file_inode(file), ret,
+                                         cachefiles_trace_trunc_error);
+               cachefiles_io_error_obj(object, "Trunc-to-size failed %d", ret);
+               cachefiles_remove_object_xattr(cache, object, file->f_path.dentry);
+               return false;
+       }
+
+       if (new_size < dio_size) {
+               trace_cachefiles_trunc(object, inode, dio_size, new_size,
+                                      cachefiles_trunc_dio_adjust);
+               ret = cachefiles_inject_write_error();
+               if (ret == 0)
+                       ret = vfs_fallocate(file, FALLOC_FL_ZERO_RANGE,
+                                           new_size, dio_size);
+               if (ret < 0) {
+                       trace_cachefiles_io_error(object, file_inode(file), ret,
+                                                 cachefiles_trace_fallocate_error);
+                       cachefiles_io_error_obj(object, "Trunc-to-dio-size failed %d", ret);
+                       cachefiles_remove_object_xattr(cache, object, file->f_path.dentry);
+                       return false;
+               }
+       }
+
+       return true;
+}
+
+/*
+ * Resize the backing object.
+ */
+static void cachefiles_resize_cookie(struct netfs_cache_resources *cres,
+                                    loff_t new_size)
+{
+       struct cachefiles_object *object = cachefiles_cres_object(cres);
+       struct cachefiles_cache *cache = object->volume->cache;
+       struct fscache_cookie *cookie = object->cookie;
+       const struct cred *saved_cred;
+       struct file *file = cachefiles_cres_file(cres);
+       loff_t old_size = cookie->object_size;
+
+       _enter("%llu->%llu", old_size, new_size);
+
+       if (new_size < old_size) {
+               cachefiles_begin_secure(cache, &saved_cred);
+               cachefiles_shorten_object(object, file, new_size);
+               cachefiles_end_secure(cache, saved_cred);
+               object->cookie->object_size = new_size;
+               return;
+       }
+
+       /* The file is being expanded.  We don't need to do anything
+        * particularly.  cookie->initial_size doesn't change and so the point
+        * at which we have to download before doesn't change.
+        */
+       cookie->object_size = new_size;
+}
+
 /*
  * Commit changes to the object as we drop it.
  */
@@ -363,5 +440,6 @@ const struct fscache_cache_ops cachefiles_cache_ops = {
        .withdraw_cookie        = cachefiles_withdraw_cookie,
        .invalidate_cookie      = cachefiles_invalidate_cookie,
        .begin_operation        = cachefiles_begin_operation,
+       .resize_cookie          = cachefiles_resize_cookie,
        .prepare_to_write       = cachefiles_prepare_to_write,
 };