From 81aec05103558f57adb10fd319847304cdf44aa7 Mon Sep 17 00:00:00 2001 From: Bobi Jam Date: Fri, 3 Sep 2021 00:38:43 +0800 Subject: [PATCH] LU-14713 llite: tighten condition for fault not drop mmap_sem As __lock_page_or_retry() indicates, filemap_fault() will return VM_FAULT_RETRY without releasing mmap_sem iff flags contains FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT. So ll_fault0() should pass in FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT in ll_filemap_fault() so that when it returns VM_FAULT_RETRY, we can pass on trying normal fault under DLM lock as mmap_sem is still being held. While in Linux 5.1 (6b4c9f4469819) FAULT_FLAG_RETRY_NOWAIT is enough to not drop mmap_sem when failed to lock the page. Fixes: 87865e4ae9 ("LU-13182 llite: Avoid eternel retry loops with MAP_POPULATE") Signed-off-by: Bobi Jam Change-Id: I9420c587301722b597155558657577349a8141e4 Reviewed-on: https://review.whamcloud.com/44715 Reviewed-by: Patrick Farrell Tested-by: jenkins Reviewed-by: Neil Brown Tested-by: Maloo Reviewed-by: Oleg Drokin --- lustre/llite/llite_mmap.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/lustre/llite/llite_mmap.c b/lustre/llite/llite_mmap.c index 982002c..203a56c 100644 --- a/lustre/llite/llite_mmap.c +++ b/lustre/llite/llite_mmap.c @@ -279,15 +279,23 @@ static vm_fault_t ll_fault0(struct vm_area_struct *vma, struct vm_fault *vmf) if (ll_sbi_has_fast_read(ll_i2sbi(inode))) { /* do fast fault */ + bool allow_retry = vmf->flags & FAULT_FLAG_ALLOW_RETRY; bool has_retry = vmf->flags & FAULT_FLAG_RETRY_NOWAIT; /* To avoid loops, instruct downstream to not drop mmap_sem */ - vmf->flags |= FAULT_FLAG_RETRY_NOWAIT; + /** + * only need FAULT_FLAG_ALLOW_RETRY prior to Linux 5.1 + * (6b4c9f4469819), where FAULT_FLAG_RETRY_NOWAIT is enough + * to not drop mmap_sem when failed to lock the page. + */ + vmf->flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT; ll_cl_add(inode, env, NULL, LCC_MMAP); fault_ret = ll_filemap_fault(vma, vmf); ll_cl_remove(inode, env); if (!has_retry) vmf->flags &= ~FAULT_FLAG_RETRY_NOWAIT; + if (!allow_retry) + vmf->flags &= ~FAULT_FLAG_ALLOW_RETRY; /* - If there is no error, then the page was found in cache and * uptodate; -- 1.8.3.1