From: Jens Axboe <jens.axboe@oracle.com>
Date: Wed, 20 Feb 2008 09:34:51 +0000 (+0100)
Subject: splice: only return -EAGAIN if there's hope of more data
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=02cf01aea5af7a4d1a38045712fe11bffcc206b0;p=GitHub%2FLineageOS%2Fandroid_kernel_samsung_universal7580.git

splice: only return -EAGAIN if there's hope of more data

sys_tee() currently is a bit eager in returning -EAGAIN, it may do so
even if we don't have a chance of anymore data becoming available. So
improve the logic and only return -EAGAIN if we have an attached writer
to the input pipe.

Reported by Johann Felix Soden <johfel@gmx.de> and
Patrick McManus <mcmanus@ducksong.com>.

Tested-by: Johann Felix Soden <johfel@users.sourceforge.net>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---

diff --git a/fs/splice.c b/fs/splice.c
index 9b559ee711a..0670c915cd3 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1669,6 +1669,13 @@ static int link_pipe(struct pipe_inode_info *ipipe,
 		i++;
 	} while (len);
 
+	/*
+	 * return EAGAIN if we have the potential of some data in the
+	 * future, otherwise just return 0
+	 */
+	if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
+		ret = -EAGAIN;
+
 	inode_double_unlock(ipipe->inode, opipe->inode);
 
 	/*
@@ -1709,11 +1716,8 @@ static long do_tee(struct file *in, struct file *out, size_t len,
 		ret = link_ipipe_prep(ipipe, flags);
 		if (!ret) {
 			ret = link_opipe_prep(opipe, flags);
-			if (!ret) {
+			if (!ret)
 				ret = link_pipe(ipipe, opipe, len, flags);
-				if (!ret && (flags & SPLICE_F_NONBLOCK))
-					ret = -EAGAIN;
-			}
 		}
 	}