[dpdk-dev] [PATCH 3/3] memalloc: fix unmapping and marking segments as free

[Anatoly Burakov <anatoly.burakov@intel.com>]

Currently, page deallocation might fail if allocator cannot get page
fd, which will leave VA space still mapped, and will also not mark
page as free.

Fix page deallocation function to always unmap space before trying
to get rid of the page itself, and always mark page as free even if
page deallocation failed.

Fixes: a5ff05d60fc5 ("mem: support unmapping pages at runtime")
Fixes: 1a7dc2252f28 ("mem: revert to using flock and add per-segment lockfiles")
Cc: anatoly.burakov@intel.com

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
---
 lib/librte_eal/linuxapp/eal/eal_memalloc.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/lib/librte_eal/linuxapp/eal/eal_memalloc.c b/lib/librte_eal/linuxapp/eal/eal_memalloc.c
index 3282293..c1a0211 100644
--- a/lib/librte_eal/linuxapp/eal/eal_memalloc.c
+++ b/lib/librte_eal/linuxapp/eal/eal_memalloc.c
@@ -610,14 +610,6 @@ free_seg(struct rte_memseg *ms, struct hugepage_info *hi,
 	/* erase page data */
 	memset(ms->addr, 0, ms->len);
 
-	/* if we are not in single file segments mode, we're going to unmap the
-	 * segment and thus drop the lock on original fd, so take out another
-	 * shared lock before we do that.
-	 */
-	fd = get_seg_fd(path, sizeof(path), hi, list_idx, seg_idx);
-	if (fd < 0)
-		return -1;
-
 	if (mmap(ms->addr, ms->len, PROT_READ,
 			MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0) ==
 				MAP_FAILED) {
@@ -625,6 +617,14 @@ free_seg(struct rte_memseg *ms, struct hugepage_info *hi,
 		return -1;
 	}
 
+	/* if we are not in single file segments mode, we're going to unmap the
+	 * segment and thus drop the lock on original fd, but hugepage dir is
+	 * now locked so we can take out another one without races.
+	 */
+	fd = get_seg_fd(path, sizeof(path), hi, list_idx, seg_idx);
+	if (fd < 0)
+		return -1;
+
 	if (internal_config.single_file_segments) {
 		map_offset = seg_idx * ms->len;
 		if (resize_hugefile(fd, path, list_idx, seg_idx, map_offset,
@@ -735,12 +735,13 @@ alloc_seg_walk(const struct rte_memseg_list *msl, void *arg)
 						&cur_msl->memseg_arr;
 
 				tmp = rte_fbarray_get(arr, j);
-				if (free_seg(tmp, wa->hi, msl_idx, j)) {
-					RTE_LOG(ERR, EAL, "Cannot free page\n");
-					continue;
-				}
-
 				rte_fbarray_set_free(arr, j);
+
+				/* free_seg may attempt to create a file, which
+				 * may fail.
+				 */
+				if (free_seg(tmp, wa->hi, msl_idx, j))
+					RTE_LOG(DEBUG, EAL, "Cannot free page\n");
 			}
 			/* clear the list */
 			if (wa->ms)
-- 
2.7.4