On 05/03/2012 04:46 AM, Andrew Morton wrote: > On Wed, 2 May 2012 13:28:09 +0900 > Minchan Kim <minchan@xxxxxxxxxx> 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 in __vmalloc_node_range to detect it and >> to be fixed hopely. __vmalloc_node_range isn't random chocie because >> all caller which has gfp_mask of map_vm_area use it through __vmalloc_area_node. >> And __vmalloc_area_node is current static function and is called by only >> __vmalloc_node_range. So warning in __vmalloc_node_range would cover all >> vmalloc functions which have gfp_t argument. >> >> I Cced related maintainers. >> If I miss someone, please Cced them. >> >> --- a/mm/vmalloc.c >> +++ b/mm/vmalloc.c >> @@ -1648,6 +1648,10 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align, >> void *addr; >> unsigned long real_size = size; >> >> + WARN_ON_ONCE(!(gfp_mask & __GFP_WAIT) || >> + !(gfp_mask & __GFP_IO) || >> + !(gfp_mask & __GFP_FS)); >> + >> size = PAGE_ALIGN(size); >> if (!size || (size >> PAGE_SHIFT) > totalram_pages) >> goto fail; > > Well. What are we actually doing here? Causing the kernel to spew a > warning due to known-buggy callsites, so that users will report the > warnings, eventually goading maintainers into fixing their stuff. > > This isn't very efficient :( Yes. I hope maintainers fix it before merging this. > > It would be better to fix that stuff first, then add the warning to > prevent reoccurrences. Yes, maintainers are very naughty and probably > do need cattle prods^W^W warnings to motivate them to fix stuff, but we > should first make an effort to get these things fixed without > irritating and alarming our users. > > Where are these offending callsites? dm: __alloc_buffer_wait_no_callback ubi: ubi_dbg_check_write ubi_dbg_check_all_ff ext4 : ext4_kvmalloc gfs2 : gfs2_alloc_sort_buffer ntfs : __ntfs_malloc ubifs : dbg_dump_leb scan_check_cb dump_lpt_leb dbg_check_ltab_lnum dbg_scan_orphans mm : alloc_large_system_hash ceph : fill_inode ceph_setxattr ceph_removexattr ceph_x_build_authorizer ceph_decode_buffer ceph_alloc_middle > > -- > 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> > -- Kind regards, Minchan Kim -- 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>