From: Bruno Faccini <bruno.faccini@intel.com>
Date: Mon, 11 Dec 2017 09:55:32 +0000 (+0100)
Subject: LU-10149 llite: avoid live-lock when concurrent mmap()s
X-Git-Tag: 2.10.57~71
X-Git-Url: https://git.whamcloud.com/gitweb?a=commitdiff_plain;h=refs%2Fchanges%2F65%2F30465%2F2;p=fs%2Flustre-release.git

LU-10149 llite: avoid live-lock when concurrent mmap()s

Patch is an attempt to delay page-fault retry from Client side for
inode with extents being mmap()'ed, to prevent live-lock situation
to occur with other page's competitors.

Signed-off-by: Bruno Faccini <bruno.faccini@intel.com>
Change-Id: Id04664fce1a5dad4dbdd7ad4b183dffb8e38b844
Reviewed-on: https://review.whamcloud.com/30465
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
---

diff --git a/lustre/llite/llite_mmap.c b/lustre/llite/llite_mmap.c
index e76f3e4..6eaeb46 100644
--- a/lustre/llite/llite_mmap.c
+++ b/lustre/llite/llite_mmap.c
@@ -159,7 +159,7 @@ static int ll_page_mkwrite0(struct vm_area_struct *vma, struct page *vmpage,
 	int                      result;
 	__u16			 refcheck;
 	sigset_t		 set;
-	struct inode             *inode;
+	struct inode             *inode = NULL;
 	struct ll_inode_info     *lli;
 	ENTRY;
 
@@ -231,6 +231,16 @@ out:
 	CDEBUG(D_MMAP, "%s mkwrite with %d\n", current->comm, result);
 	LASSERT(ergo(result == 0, PageLocked(vmpage)));
 
+	/* if page has been unmapped, presumably due to lock reclaim for
+	 * concurrent usage, add some delay before retrying to prevent
+	 * entering live-lock situation with competitors
+	 */
+	if (result == -ENODATA && inode != NULL) {
+		CDEBUG(D_MMAP, "delaying new page-fault for inode %p to "
+			       "prevent live-lock\n", inode);
+		msleep(10);
+	}
+
 	return result;
 }