4.9-stable review patch. If anyone has any objections, please let me know.
------------------ From: chenjie <[email protected]> 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. [[email protected]: rewrite changelog] Link: http://lkml.kernel.org/r/[email protected] Fixes: fe77ba6f4f97 ("[PATCH] xip: madvice/fadvice: execute in place") Signed-off-by: chenjie <[email protected]> Signed-off-by: guoxuenan <[email protected]> Acked-by: Michal Hocko <[email protected]> Cc: Minchan Kim <[email protected]> Cc: zhangyi (F) <[email protected]> Cc: Miao Xie <[email protected]> Cc: Mike Rapoport <[email protected]> Cc: Shaohua Li <[email protected]> Cc: Andrea Arcangeli <[email protected]> Cc: Mel Gorman <[email protected]> Cc: Kirill A. Shutemov <[email protected]> Cc: David Rientjes <[email protected]> Cc: Anshuman Khandual <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Carsten Otte <[email protected]> Cc: Dan Williams <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- mm/madvise.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/mm/madvise.c +++ b/mm/madvise.c @@ -228,15 +228,14 @@ 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; @@ -251,7 +250,6 @@ 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;
