commit d2988bd412fac87859f0b68f5ea328fb0f09c216
author Al Viro <viro@zeniv.linux.org.uk> Sat May 26 19:13:10 2018 -0400
committer Al Viro <viro@zeniv.linux.org.uk> Tue May 29 23:18:17 2018 -0400
tree 1a0df5ecf1d4c9400613e328e02d204ca01aa7a2
parent 9061d14a8a97009085242b284b5b5f668af2bf97

aio_read_events_ring(): make a bit more readable

The logics for 'avail' is
	* not past the tail of cyclic buffer
	* no more than asked
	* not past the end of buffer
	* not past the end of a page

Unobfuscate the last part.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/aio.c

diff --git a/fs/aio.c b/fs/aio.c
index 6098b6b..06761d5 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1197,14 +1197,13 @@ static long aio_read_events_ring(struct kioctx *ctx,
 		if (head == tail)
 			break;
 
-		avail = min(avail, nr - ret);
-		avail = min_t(long, avail, AIO_EVENTS_PER_PAGE -
-			    ((head + AIO_EVENTS_OFFSET) % AIO_EVENTS_PER_PAGE));
-
 		pos = head + AIO_EVENTS_OFFSET;
 		page = ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE];
 		pos %= AIO_EVENTS_PER_PAGE;
 
+		avail = min(avail, nr - ret);
+		avail = min_t(long, avail, AIO_EVENTS_PER_PAGE - pos);
+
 		ev = kmap(page);
 		copy_ret = copy_to_user(event + ret, ev + pos,
 					sizeof(*ev) * avail);