From 21ac419d37f307fee4ba88d37c0bf1da0c591bac Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones@redhat.com>
Date: Tue, 1 Apr 2025 11:07:51 +0100
Subject: [PATCH] file: Hard error if sync_file_range fails

After discussion with Dave Chinner, it appears that I/O errors can be
returned by sync_file_range, ie. it is not merely a hint to start the
eviction.  Therefore return a hard error if any of the sync_file_range
calls fails.

Thanks: Dave Chinner
Updates: commit d35f0636373e6a58c8f3fcfcf505af248e27c574
(cherry picked from commit d2ed6a839c3ed50b417f45dc13e5b811ecdc4e74)
---
 plugins/file/file.c | 53 ++++++++++++++++++++++++---------------------
 1 file changed, 28 insertions(+), 25 deletions(-)

diff --git a/plugins/file/file.c b/plugins/file/file.c
index 0271a56b..aa552037 100644
--- a/plugins/file/file.c
+++ b/plugins/file/file.c
@@ -118,7 +118,7 @@ struct write_window {
 static pthread_mutex_t window_lock = PTHREAD_MUTEX_INITIALIZER;
 static struct write_window window[NR_WINDOWS];
 
-static void
+static int
 evict_writes (int fd, uint64_t offset, size_t len)
 {
   ACQUIRE_LOCK_FOR_CURRENT_SCOPE (&window_lock);
@@ -127,31 +127,32 @@ evict_writes (int fd, uint64_t offset, size_t len)
    * (asynchronously).
    */
   if (sync_file_range (fd, offset, len, SYNC_FILE_RANGE_WRITE) == -1) {
-    /* sync_file_range to start the write failed */
-    nbdkit_debug ("sync_file_range: write: (ignored): %m");
+    nbdkit_error ("sync_file_range: cache=none: starting eviction: %m");
+    return -1;
   }
-  else {
-    /* sync_file_range to start the write succeeded, so
-     * evict the oldest window from the page cache.
-     */
-    if (window[0].len > 0) {
-      if (sync_file_range (window[0].fd, window[0].offset, window[0].len,
-                           SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|
-                           SYNC_FILE_RANGE_WAIT_AFTER) == -1)
-        nbdkit_debug ("sync_file_range: wait: (ignored): %m");
-      if (posix_fadvise (window[0].fd, window[0].offset, window[0].len,
-                         POSIX_FADV_DONTNEED) == -1)
-        nbdkit_debug ("posix_fadvise: POSIX_FADV_DONTNEED: (ignored): %m");
+
+  /* Evict the oldest window from the page cache. */
+  if (window[0].len > 0) {
+    if (sync_file_range (window[0].fd, window[0].offset, window[0].len,
+                         SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|
+                         SYNC_FILE_RANGE_WAIT_AFTER) == -1) {
+      nbdkit_error ("sync_file_range: cache=none: evicting oldest window: %m");
+      return -1;
     }
-
-    /* Move the Nth window to N-1. */
-    memmove (&window[0], &window[1], sizeof window[0] * (NR_WINDOWS-1));
-
-    /* Add the range to the newest end of the list of windows. */
-    window[NR_WINDOWS-1].fd = fd;
-    window[NR_WINDOWS-1].offset = offset;
-    window[NR_WINDOWS-1].len = len;
+    if (posix_fadvise (window[0].fd, window[0].offset, window[0].len,
+                       POSIX_FADV_DONTNEED) == -1)
+      nbdkit_debug ("posix_fadvise: POSIX_FADV_DONTNEED: (ignored): %m");
   }
+
+  /* Move the Nth window to N-1. */
+  memmove (&window[0], &window[1], sizeof window[0] * (NR_WINDOWS-1));
+
+  /* Add the range to the newest end of the list of windows. */
+  window[NR_WINDOWS-1].fd = fd;
+  window[NR_WINDOWS-1].offset = offset;
+  window[NR_WINDOWS-1].len = len;
+
+  return 0;
 }
 
 /* When we close the handle we must remove any windows which are still
@@ -920,8 +921,10 @@ file_pwrite (void *handle, const void *buf, uint32_t count, uint64_t offset,
     return -1;
 
 #if EVICT_WRITES
-  if (cache_mode == cache_none)
-    evict_writes (h->fd, orig_offset, orig_count);
+  if (cache_mode == cache_none) {
+    if (evict_writes (h->fd, orig_offset, orig_count) == -1)
+      return -1;
+  }
 #endif
 
   return 0;
-- 
2.47.1