From e12c861e687364ff5a891f0ae90283b384d74197 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Wed, 6 Nov 2019 15:30:26 +0100 Subject: [PATCH] mm: Don't bother dropping mmap_sem for zero size readahead When handling a page fault, we drop mmap_sem to start async readahead so that we don't block on IO submission with mmap_sem held. However there's no point to drop mmap_sem in case readahead is disabled. Handle that case to avoid pointless dropping of mmap_sem and retrying the fault. Signed-off-by: Jan Kara --- mm/filemap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/filemap.c b/mm/filemap.c index 1146fcfa3215..3d39c437b07e 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2458,7 +2458,7 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf, pgoff_t offset = vmf->pgoff; /* If we don't want any read-ahead, don't bother */ - if (vmf->vma->vm_flags & VM_RAND_READ) + if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages) return fpin; if (ra->mmap_miss > 0) ra->mmap_miss--; -- 2.16.4