From: Greg KH <[email protected]> 3.4-stable review patch. If anyone has any objections, please let me know.
------------------ From: Jeff Layton <[email protected]> commit 3ae629d98bd5ed77585a878566f04f310adbc591 upstream. 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. Reported-by: Jian Li <[email protected]> Signed-off-by: Jeff Layton <[email protected]> Signed-off-by: Steve French <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- fs/cifs/connect.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -3348,6 +3348,18 @@ void cifs_setup_cifs_sb(struct smb_vol * #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) { @@ -3378,6 +3390,9 @@ cifs_negotiate_wsize(struct cifs_tcon *t 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); @@ -3419,6 +3434,9 @@ cifs_negotiate_rsize(struct cifs_tcon *t 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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
