On Wed, Jan 03, 2018 at 04:17:53PM -0800, Andrew Morton wrote: > : invalidate_mapping_pages() takes start/end, but fadvise is currently passing > : it start/len. > : > : > : > : mm/fadvise.c | 8 ++++++-- > : 1 files changed, 6 insertions(+), 2 deletions(-) > : > : diff -puN mm/fadvise.c~fadvise-fix mm/fadvise.c > : --- 25/mm/fadvise.c~fadvise-fix 2003-08-14 18:16:12.000000000 -0700 > : +++ 25-akpm/mm/fadvise.c 2003-08-14 18:16:12.000000000 -0700 > : @@ -26,6 +26,8 @@ long sys_fadvise64(int fd, loff_t offset > : struct inode *inode; > : struct address_space *mapping; > : struct backing_dev_info *bdi; > : + pgoff_t start_index; > : + pgoff_t end_index; > : int ret = 0; > : > : if (!file) > : @@ -65,8 +67,10 @@ long sys_fadvise64(int fd, loff_t offset > : case POSIX_FADV_DONTNEED: > : if (!bdi_write_congested(mapping->backing_dev_info)) > : filemap_flush(mapping); > : - invalidate_mapping_pages(mapping, offset >> PAGE_CACHE_SHIFT, > : - (len >> PAGE_CACHE_SHIFT) + 1); > : + start_index = offset >> PAGE_CACHE_SHIFT; > : + end_index = (offset + len + PAGE_CACHE_SIZE - 1) >> > : + PAGE_CACHE_SHIFT; > : + invalidate_mapping_pages(mapping, start_index, end_index); > : break; > : default: > : ret = -EINVAL; > : > > So I'm not sure that the whole "don't discard partial pages" thing is > well-founded and I see no reason why we cannot alter it. > > So, thinking caps on: why not just discard them? After all, that's > what userspace asked us to do. >
We could, it just means that any application that accidentally discards hot data due to an unaligned fadvise will incur more IO. We've no idea how many, if any applications, do this. -- Mel Gorman SUSE Labs
