From 10c12851a022662bf6085bd4384b4ebed4c447ce Mon Sep 17 00:00:00 2001 From: Ilya Dryomov Date: Fri, 30 Aug 2019 20:44:24 +0200 Subject: [PATCH] libceph: avoid a __vmalloc() deadlock in ceph_kvmalloc() The vmalloc allocator doesn't fully respect the specified gfp mask: while the actual pages are allocated as requested, the page table pages are always allocated with GFP_KERNEL. ceph_kvmalloc() may be called with GFP_NOFS and GFP_NOIO (for ceph and rbd respectively), so this may result in a deadlock. There is no real reason for the current PAGE_ALLOC_COSTLY_ORDER logic, it's just something that seemed sensible at the time (ceph_kvmalloc() predates kvmalloc()). kvmalloc() is smarter: in an attempt to reduce long term fragmentation, it first tries to kmalloc non-disruptively. Switch to kvmalloc() and set the respective PF_MEMALLOC_* flag using the scope API to avoid the deadlock. Note that kvmalloc() needs to be passed GFP_KERNEL to enable the fallback. Signed-off-by: Ilya Dryomov Reviewed-by: Jeff Layton --- net/ceph/ceph_common.c | 29 +++++++++++++++++++++++------ 1 file changed, 23 insertions(+), 6 deletions(-) diff --git a/net/ceph/ceph_common.c b/net/ceph/ceph_common.c index b412a3c..2d56824 100644 --- a/net/ceph/ceph_common.c +++ b/net/ceph/ceph_common.c @@ -13,6 +13,7 @@ #include #include #include +#include #include #include #include @@ -185,18 +186,34 @@ int ceph_compare_options(struct ceph_options *new_opt, } EXPORT_SYMBOL(ceph_compare_options); +/* + * kvmalloc() doesn't fall back to the vmalloc allocator unless flags are + * compatible with (a superset of) GFP_KERNEL. This is because while the + * actual pages are allocated with the specified flags, the page table pages + * are always allocated with GFP_KERNEL. map_vm_area() doesn't even take + * flags because GFP_KERNEL is hard-coded in {p4d,pud,pmd,pte}_alloc(). + * + * ceph_kvmalloc() may be called with GFP_KERNEL, GFP_NOFS or GFP_NOIO. + */ void *ceph_kvmalloc(size_t size, gfp_t flags) { - if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) { - void *ptr = kmalloc(size, flags | __GFP_NOWARN); - if (ptr) - return ptr; + void *p; + + if ((flags & (__GFP_IO | __GFP_FS)) == (__GFP_IO | __GFP_FS)) { + p = kvmalloc(size, flags); + } else if ((flags & (__GFP_IO | __GFP_FS)) == __GFP_IO) { + unsigned int nofs_flag = memalloc_nofs_save(); + p = kvmalloc(size, GFP_KERNEL); + memalloc_nofs_restore(nofs_flag); + } else { + unsigned int noio_flag = memalloc_noio_save(); + p = kvmalloc(size, GFP_KERNEL); + memalloc_noio_restore(noio_flag); } - return __vmalloc(size, flags, PAGE_KERNEL); + return p; } - static int parse_fsid(const char *str, struct ceph_fsid *fsid) { int i = 0; -- 2.7.4