add a vfs_fsync helper
Fsync currently has a fdatawrite/fdatawait pair around the method call,
and a mutex_lock/unlock of the inode mutex. All callers of fsync have
to duplicate this, but we have a few and most of them don't quite get
it right. This patch adds a new vfs_fsync that takes care of this.
It's a little more complicated as usual as ->fsync might get a NULL file
pointer and just a dentry from nfsd, but otherwise gets afile and we
want to take the mapping and file operations from it when it is there.
Notes on the fsync callers:
- ecryptfs wasn't calling filemap_fdatawrite / filemap_fdatawait on the
lower file
- coda wasn't calling filemap_fdatawrite / filemap_fdatawait on the host
file, and returning 0 when ->fsync was missing
- shm wasn't calling either filemap_fdatawrite / filemap_fdatawait nor
taking i_mutex. Now given that shared memory doesn't have disk
backing not doing anything in fsync seems fine and I left it out of
the vfs_fsync conversion for now, but in that case we might just
not pass it through to the lower file at all but just call the no-op
simple_sync_file directly.
[and now actually export vfs_fsync]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/sync.c b/fs/sync.c
index 2967562..0921d6d 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -75,14 +75,39 @@
return ret;
}
-long do_fsync(struct file *file, int datasync)
+/**
+ * vfs_fsync - perform a fsync or fdatasync on a file
+ * @file: file to sync
+ * @dentry: dentry of @file
+ * @data: only perform a fdatasync operation
+ *
+ * Write back data and metadata for @file to disk. If @datasync is
+ * set only metadata needed to access modified file data is written.
+ *
+ * In case this function is called from nfsd @file may be %NULL and
+ * only @dentry is set. This can only happen when the filesystem
+ * implements the export_operations API.
+ */
+int vfs_fsync(struct file *file, struct dentry *dentry, int datasync)
{
- int ret;
- int err;
- struct address_space *mapping = file->f_mapping;
+ const struct file_operations *fop;
+ struct address_space *mapping;
+ int err, ret;
- if (!file->f_op || !file->f_op->fsync) {
- /* Why? We can still call filemap_fdatawrite */
+ /*
+ * Get mapping and operations from the file in case we have
+ * as file, or get the default values for them in case we
+ * don't have a struct file available. Damn nfsd..
+ */
+ if (file) {
+ mapping = file->f_mapping;
+ fop = file->f_op;
+ } else {
+ mapping = dentry->d_inode->i_mapping;
+ fop = dentry->d_inode->i_fop;
+ }
+
+ if (!fop || !fop->fsync) {
ret = -EINVAL;
goto out;
}
@@ -94,7 +119,7 @@
* livelocks in fsync_buffers_list().
*/
mutex_lock(&mapping->host->i_mutex);
- err = file->f_op->fsync(file, file->f_path.dentry, datasync);
+ err = fop->fsync(file, dentry, datasync);
if (!ret)
ret = err;
mutex_unlock(&mapping->host->i_mutex);
@@ -104,15 +129,16 @@
out:
return ret;
}
+EXPORT_SYMBOL(vfs_fsync);
-static long __do_fsync(unsigned int fd, int datasync)
+static int do_fsync(unsigned int fd, int datasync)
{
struct file *file;
int ret = -EBADF;
file = fget(fd);
if (file) {
- ret = do_fsync(file, datasync);
+ ret = vfs_fsync(file, file->f_path.dentry, datasync);
fput(file);
}
return ret;
@@ -120,12 +146,12 @@
asmlinkage long sys_fsync(unsigned int fd)
{
- return __do_fsync(fd, 0);
+ return do_fsync(fd, 0);
}
asmlinkage long sys_fdatasync(unsigned int fd)
{
- return __do_fsync(fd, 1);
+ return do_fsync(fd, 1);
}
/*