libnbd/0003-Revert-copy-file-ops.c-Remove-unneeded-check.patch

From 4e456ff6363580177ceffdad79b8fc1e8c7f35eb Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones@redhat.com>
Date: Wed, 3 Mar 2021 10:12:31 +0000
Subject: [PATCH 3/6] Revert "copy: file-ops.c: Remove unneeded check"

This reverts commit 0f6e4f38bc440fc52c20a3a448ef031f806ec5e2.

This fails on ppc64le only with:

lt-nbdcopy: file-ops.c:136: page_was_cached: Assertion `page < rwf->cached_pages.size' failed.

Coincidentally this is the only architecture on Fedora that uses a 64K
page size, although I don't know if that is connected.  I was not able
to make this fail on x86.
---
 copy/file-ops.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/copy/file-ops.c b/copy/file-ops.c
index 47ec768..ea725a4 100644
--- a/copy/file-ops.c
+++ b/copy/file-ops.c
@@ -102,7 +102,7 @@ page_size_init (void)
 /* Load the page cache map for a particular file into
  * rwf->cached_pages.  Only used when reading files.  This doesn't
  * fail: if a system call fails then rwf->cached_pages.size will be
- * zero which is handled in page_cache_evict.
+ * zero which is handled in page_was_cached.
  */
 static inline void
 page_cache_map (struct rw_file *rwf)
@@ -126,16 +126,19 @@ page_cache_map (struct rw_file *rwf)
   munmap (ptr, rwf->rw.size);
 }
 
-/* Test if a single page of the file was cached before nbdcopy ran.
- * Valid only if we mapped the cached pages.
- */
+/* Test if a single page of the file was cached before nbdcopy ran. */
 static inline bool
 page_was_cached (struct rw_file *rwf, uint64_t offset)
 {
   uint64_t page = offset / page_size;
-  assert (page < rwf->cached_pages.size);
-
-  return (rwf->cached_pages.ptr[page] & 1) != 0;
+  if (page < rwf->cached_pages.size)
+    return (rwf->cached_pages.ptr[page] & 1) != 0;
+  else
+    /* This path is taken if we didn't manage to map the input file
+     * for any reason.  In this case assume that pages were mapped so
+     * we will not evict them: essentially fall back to doing nothing.
+     */
+    return true;
 }
 
 /* Evict file contents from the page cache if they were not present in
@@ -147,10 +150,6 @@ page_cache_evict (struct rw_file *rwf, uint64_t orig_offset, size_t orig_len)
   uint64_t offset, n;
   size_t len;
 
-  /* If we didn't manage to map the input file for any reason, assume
-   * that pages were mapped so we will not evict them: essentially fall
-   * back to doing nothing.
-   */
   if (rwf->cached_pages.size == 0) return;
 
   /* Only bother with whole pages. */
-- 
2.29.0.rc2