[PATCH AUTOSEL 5.3 11/71] fuse: fix request limit

Sasha Levin
2019-10-01T16:39:45Z

From: Miklos Szeredi <mszeredi@redhat.com>

[ Upstream commit f22f812d5ce75a18b56073a7a63862e6ea764070 ]

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: Sasha Levin <sashal@kernel.org>
---
fs/fuse/inode.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 4bb885b0f0322..04b10b3b8741b 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -822,9 +822,12 @@ static const struct super_operations fuse_super_operations = {

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;
--
2.20.1