[PATCH 4/4] xmmap: inform Linux users of tuning knobs on ENOMEM

From: Eric Wong <e@80x24.org>
Date: Jun 29, 2021, 08:11 UTC
Message-ID: <20210629081108.28657-5-e@80x24.org>
In-Reply-To: <20210629081108.28657-1-e@80x24.org>

In cases where we can't (or haven't gotten around to) attempting graceful handling of mmap failures, Linux users may benefit from additional information on how to avoid the problem.

Signed-off-by: Eric Wong <e@80x24.org>
---
 object-file.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/object-file.c b/object-file.c
index 4c043f1f3c..4139a5ebe6 100644
--- a/object-file.c
+++ b/object-file.c
@@ -1027,8 +1027,14 @@ void *xmmap(void *start, size_t length,
 	int prot, int flags, int fd, off_t offset)
 {
 	void *ret = xmmap_gently(start, length, prot, flags, fd, offset);
-	if (ret == MAP_FAILED)
+	if (ret == MAP_FAILED) {
+#if defined(__linux__)
+		if (errno == ENOMEM)
+			die_errno(_(
+"mmap failed, check sys.vm.max_map_count and/or RLIMIT_DATA"));
+#endif /* OS-specific bits */
 		die_errno(_("mmap failed"));
+	}
 	return ret;
 }