From: Miklos Szeredi <mszeredi@redhat.com>
Date: Thu, 12 Sep 2019 14:28:13 +0200
Subject: fuse: fix request limit
Git-commit: f22f812d5ce75a18b56073a7a63862e6ea764070
Patch-mainline: 5.4-rc1
References: bnc#1151927 5.3.6

The size of struct fuse_req was reduced from 392B to 144B on a non-debug
config, thus the sanitize_global_limit() helper was setting a larger
default limit.  This doesn't really reflect reduction in the memory used by
requests, since the fields removed from fuse_req were added to fuse_args
derived structs; e.g. sizeof(struct fuse_writepages_args) is 248B, thus
resulting in slightly more memory being used for writepage requests
overalll (due to using 256B slabs).

Make the calculatation ignore the size of fuse_req and use the old 392B
value.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 fs/fuse/inode.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -823,9 +823,12 @@ static const struct super_operations fus
 
 static void sanitize_global_limit(unsigned *limit)
 {
+	/*
+	 * The default maximum number of async requests is calculated to consume
+	 * 1/2^13 of the total memory, assuming 392 bytes per request.
+	 */
 	if (*limit == 0)
-		*limit = ((totalram_pages() << PAGE_SHIFT) >> 13) /
-			 sizeof(struct fuse_req);
+		*limit = ((totalram_pages() << PAGE_SHIFT) >> 13) / 392;
 
 	if (*limit >= 1 << 16)
 		*limit = (1 << 16) - 1;