Re: [PATCH 2/2] fuse: wait for writeback in fuse_file_fallocate()

From: Maxim Patlasov
Date: Tue Aug 13 2013 - 08:56:45 EST


08/13/2013 04:05 PM, Brian Foster ÐÐÑÐÑ:
@@ -2478,8 +2516,11 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
if (lock_inode) {
- if (mode & FALLOC_FL_PUNCH_HOLE)
- fuse_set_nowrite(inode);
+ if (mode & FALLOC_FL_PUNCH_HOLE) {
+ truncate_pagecache_range(inode, offset,
+ offset + length - 1);
+ fuse_wait_on_writeback(inode, offset, length);
+ }
If this happens to be the first attempt on an fs that doesn't support
fallocate, we'll return -EOPNOTSUPP after having already punched out the
data in the pagecache.

Yes, this is unpleasant, but it's not critical, imo. We're returning an error code (even though equal to -EOPNOTSUPP) and a sane application should not make any assumption about current state of the punched region. Also, the application intended to discard given region of the file, so why should it pay care for its content afterwards?

What about replacing the nowrite logic with a
flush (and still followed by your new writeback wait logic) rather than
moving the pagecache truncate?

The "flush" you mentioned should firstly flush page cache. invalidate_inode_pages2_range() seems to be a candidate. We definitely cannot ignore error code from it because it can be fuse_launder_page() who got -ENOMEM from fuse_writepage_locked(). In case of err == -ENOMEM, we could safely fail fallocate, but what should we do if it's -EBUSY? Any ideas?

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at