Hi, On Fri, 2012-04-27 at 17:42 +0900, Minchan Kim wrote: > Now there are several places to use __vmalloc with GFP_ATOMIC, > GFP_NOIO, GFP_NOFS but unfortunately __vmalloc calls map_vm_area > which calls alloc_pages with GFP_KERNEL to allocate page tables. > It means it's possible to happen deadlock. > I don't know why it doesn't have reported until now. > > Firstly, I tried passing gfp_t to lower functions to support __vmalloc > with such flags but other mm guys don't want and decided that > all of caller should be fixed. > > http://marc.info/?l=linux-kernel&m=133517143616544&w=2 > > To begin with, let's listen other's opinion whether they can fix it > by other approach without calling __vmalloc with such flags. > > So this patch adds warning to detect and to be fixed hopely. > I Cced related maintainers. > If I miss someone, please Cced them. > That seems ok to me. GFS2 only uses it as a back up in case the kmalloc call fails, and I suspect that we could easily eliminate it entirely since I doubt that it does actually ever fail in reality. If it were to fail then that is handled correctly anyway, Steve. > side-note: > I added WARN_ON instead of WARN_ONCE to detect all of callers > and each WARN_ON for each flag to detect to use any flag easily. > After we fix all of caller or reduce such caller, we can merge > a warning with WARN_ONCE. > > Cc: Neil Brown <neilb@xxxxxxx> > Cc: Artem Bityutskiy <dedekind1@xxxxxxxxx> > Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx> > Cc: "Theodore Ts'o" <tytso@xxxxxxx> > Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx> > Cc: Steven Whitehouse <swhiteho@xxxxxxxxxx> > Cc: "David S. Miller" <davem@xxxxxxxxxxxxx> > Cc: James Morris <jmorris@xxxxxxxxx> > Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> > Cc: Sage Weil <sage@xxxxxxxxxxxx> > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> > --- > mm/vmalloc.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 94dff88..36beccb 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -1700,6 +1700,15 @@ static void *__vmalloc_node(unsigned long size, unsigned long align, > gfp_t gfp_mask, pgprot_t prot, > int node, void *caller) > { > + /* > + * This function calls map_vm_area so that it allocates > + * page table with GFP_KERNEL so caller should avoid using > + * GFP_NOIO, GFP_NOFS and !__GFP_WAIT. > + */ > + WARN_ON(!(gfp_mask & __GFP_WAIT)); > + WARN_ON(!(gfp_mask & __GFP_IO)); > + WARN_ON(!(gfp_mask & __GFP_FS)); > + > return __vmalloc_node_range(size, align, VMALLOC_START, VMALLOC_END, > gfp_mask, prot, node, caller); > } -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>