4.4-stable review patch. If anyone has any objections, please let me know.
------------------ From: chenjie <chenj...@huawei.com> commit 6ea8d958a2c95a1d514015d4e29ba21a8c0a1a91 upstream. MADVISE_WILLNEED has always been a noop for DAX (formerly XIP) mappings. Unfortunately madvise_willneed() doesn't communicate this information properly to the generic madvise syscall implementation. The calling convention is quite subtle there. madvise_vma() is supposed to either return an error or update &prev otherwise the main loop will never advance to the next vma and it will keep looping for ever without a way to get out of the kernel. It seems this has been broken since introduction. Nobody has noticed because nobody seems to be using MADVISE_WILLNEED on these DAX mappings. [mho...@suse.com: rewrite changelog] Link: http://lkml.kernel.org/r/20171127115318.911-1-guoxue...@huawei.com Fixes: fe77ba6f4f97 ("[PATCH] xip: madvice/fadvice: execute in place") Signed-off-by: chenjie <chenj...@huawei.com> Signed-off-by: guoxuenan <guoxue...@huawei.com> Acked-by: Michal Hocko <mho...@suse.com> Cc: Minchan Kim <minc...@kernel.org> Cc: zhangyi (F) <yi.zh...@huawei.com> Cc: Miao Xie <miao...@huawei.com> Cc: Mike Rapoport <r...@linux.vnet.ibm.com> Cc: Shaohua Li <s...@fb.com> Cc: Andrea Arcangeli <aarca...@redhat.com> Cc: Mel Gorman <mgor...@techsingularity.net> Cc: Kirill A. Shutemov <kirill.shute...@linux.intel.com> Cc: David Rientjes <rient...@google.com> Cc: Anshuman Khandual <khand...@linux.vnet.ibm.com> Cc: Rik van Riel <r...@redhat.com> Cc: Carsten Otte <co...@de.ibm.com> Cc: Dan Williams <dan.j.willi...@intel.com> Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- mm/madvise.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/mm/madvise.c +++ b/mm/madvise.c @@ -223,15 +223,14 @@ static long madvise_willneed(struct vm_a { struct file *file = vma->vm_file; + *prev = vma; #ifdef CONFIG_SWAP if (!file) { - *prev = vma; force_swapin_readahead(vma, start, end); return 0; } if (shmem_mapping(file->f_mapping)) { - *prev = vma; force_shm_swapin_readahead(vma, start, end, file->f_mapping); return 0; @@ -246,7 +245,6 @@ static long madvise_willneed(struct vm_a return 0; } - *prev = vma; start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; if (end > vma->vm_end) end = vma->vm_end;
