Re: splice vs O_APPEND
From: Michael Kerrisk <hidden>
Date: 2008-10-10 10:23:58
Also in:
linux-fsdevel, lkml
Hey Linus, On Thu, Oct 9, 2008 at 11:14 PM, Linus Torvalds [off-list ref] wrote:
On Thu, 9 Oct 2008, Miklos Szeredi wrote:quoted
The thing is, the append-only attribute is absolutely useless without being able to depend on it. So in that sense I think the IS_APPEND issue is important, and I'm fine with your original proposal for that (except we don't need the IS_IMMUTABLE check).Heh. In the meantime, I had grown to hate that more complex patch. So because I do see your point with IS_APPEND (being different from O_APPEND), but because I also think that O_APPEND itself is a gray and murky area, I just committed the following. I doubt anybody will ever even notice it, but while I think it's all debatable, we might as well debate it with this in place. I do agree that it's "safer" behaviour.
Please do CC linux-api@vger (and if you are kind, me, in case something needs to go into man-pages) on interface changes. Cheers, Michael
quoted hunk
--- commit a05b4085484ac45558810e4c5928e5a291c20f65 Author: Linus Torvalds [off-list ref] Date: Thu Oct 9 14:04:54 2008 -0700 Don't allow splice() to files opened with O_APPEND This is debatable, but while we're debating it, let's disallow the combination of splice and an O_APPEND destination. It's not entirely clear what the semantics of O_APPEND should be, and POSIX apparently expects pwrite() to ignore O_APPEND, for example. So we could make up any semantics we want, including the old ones. But Miklos convinced me that we should at least give it some thought, and that accepting writes at arbitrary offsets is wrong at least for IS_APPEND() files (which always have O_APPEND set, even if the reverse isn't true: you can obviously have O_APPEND set on a regular file). So disallow O_APPEND entirely for now. I doubt anybody cares, and this way we have one less gray area to worry about. Reported-and-argued-for-by: Miklos Szeredi [off-list ref] Cc: Jens Axboe [off-list ref] Signed-off-by: Linus Torvalds [off-list ref]diff --git a/fs/splice.c b/fs/splice.c index 1bbc6f4..a1e701c 100644 --- a/fs/splice.c +++ b/fs/splice.c@@ -898,6 +898,9 @@ static long do_splice_from(struct pipe_inode_info *pipe, struct file *out, if (unlikely(!(out->f_mode & FMODE_WRITE))) return -EBADF; + if (unlikely(out->f_flags & O_APPEND)) + return -EINVAL; + ret = rw_verify_area(WRITE, out, ppos, len); if (unlikely(ret < 0)) return ret; --To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html
-- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Found a documentation bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html