Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 3ae629d9 authored by Jeff Layton's avatar Jeff Layton Committed by Steve French
Browse files

cifs: on CONFIG_HIGHMEM machines, limit the rsize/wsize to the kmap space 



We currently rely on being able to kmap all of the pages in an async
read or write request. If you're on a machine that has CONFIG_HIGHMEM
set then that kmap space is limited, sometimes to as low as 512 slots.

With 512 slots, we can only support up to a 2M r/wsize, and that's
assuming that we can get our greedy little hands on all of them. There
are other users however, so it's possible we'll end up stuck with a
size that large.

Since we can't handle a rsize or wsize larger than that currently, cap
those options at the number of kmap slots we have. We could consider
capping it even lower, but we currently default to a max of 1M. Might as
well allow those luddites on 32 bit arches enough rope to hang
themselves.

A more robust fix would be to teach the send and receive routines how
to contend with an array of pages so we don't need to marshal up a kvec
array at all. That's a fairly significant overhaul though, so we'll need
this limit in place until that's ready.

Cc: <stable@vger.kernel.org>
Reported-by: default avatarJian Li <jiali@redhat.com>
Signed-off-by: default avatarJeff Layton <jlayton@redhat.com>
Signed-off-by: default avatarSteve French <smfrench@gmail.com>
parent ffc61ccb

fs/cifs/connect.c

+18 −0
Original line number Diff line number Diff line
@@ -3445,6 +3445,18 @@ void cifs_setup_cifs_sb(struct smb_vol *pvolume_info, 
#define CIFS_DEFAULT_NON_POSIX_RSIZE (60 * 1024)

#define CIFS_DEFAULT_NON_POSIX_WSIZE (65536)



/*

 * On hosts with high memory, we can't currently support wsize/rsize that are

 * larger than we can kmap at once. Cap the rsize/wsize at

 * LAST_PKMAP * PAGE_SIZE. We'll never be able to fill a read or write request

 * larger than that anyway.

 */

#ifdef CONFIG_HIGHMEM

#define CIFS_KMAP_SIZE_LIMIT	(LAST_PKMAP * PAGE_CACHE_SIZE)

#else /* CONFIG_HIGHMEM */

#define CIFS_KMAP_SIZE_LIMIT	(1<<24)

#endif /* CONFIG_HIGHMEM */



static unsigned int

cifs_negotiate_wsize(struct cifs_tcon *tcon, struct smb_vol *pvolume_info)

{
@@ -3475,6 +3487,9 @@ cifs_negotiate_wsize(struct cifs_tcon *tcon, struct smb_vol *pvolume_info) 
		wsize = min_t(unsigned int, wsize,

				server->maxBuf - sizeof(WRITE_REQ) + 4);



	/* limit to the amount that we can kmap at once */

	wsize = min_t(unsigned int, wsize, CIFS_KMAP_SIZE_LIMIT);



	/* hard limit of CIFS_MAX_WSIZE */

	wsize = min_t(unsigned int, wsize, CIFS_MAX_WSIZE);
@@ -3516,6 +3531,9 @@ cifs_negotiate_rsize(struct cifs_tcon *tcon, struct smb_vol *pvolume_info) 
	if (!(server->capabilities & CAP_LARGE_READ_X))

		rsize = min_t(unsigned int, CIFSMaxBufSize, rsize);



	/* limit to the amount that we can kmap at once */

	rsize = min_t(unsigned int, rsize, CIFS_KMAP_SIZE_LIMIT);



	/* hard limit of CIFS_MAX_RSIZE */

	rsize = min_t(unsigned int, rsize, CIFS_MAX_RSIZE);