file->f_ra->ra_pages will remain the initialized value since it opend, which may be NOT equal to bdi->ra_pages as the latter one is updated somehow(etc, echo xxx > /sys/block/dm/queue/read_ahead_kb).So sync ra->ra_pages to the updated value when sync read. Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx> --- mm/filemap.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/filemap.c b/mm/filemap.c index d78f577..5c2d7cc 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2470,6 +2470,8 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) struct file *fpin = NULL; pgoff_t offset = vmf->pgoff; + if (ra->ra_pages != inode_to_bdi(mapping->host)->ra_pages) + ra->ra_pages = inode_to_bdi(mapping->host)->ra_pages; /* If we don't want any read-ahead, don't bother */ if (vmf->vma->vm_flags & VM_RAND_READ) return fpin; -- 1.9.1
