[RFC PATCH v2 2/7] migration: Propagate error in postcopy setup functions

[Aadeshveer Singh <aadeshveer07@gmail.com>]

Modernize error handling in postcopy_ram_incoming_setup() and
postcopy_temp_pages_setup() by replacing error_reports and local error
handling with standard Error propagation.

Replace use of strerror() on errno with error_setg_errno() for modular
handling of errors and change return values to -1 on failure as no
caller checks the actual return value.

Signed-off-by: Aadeshveer Singh <aadeshveer07@gmail.com>
---
 migration/postcopy-ram.c | 41 +++++++++++++++++-----------------------
 migration/postcopy-ram.h |  2 +-
 2 files changed, 18 insertions(+), 25 deletions(-)

diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index f5ef93f193..96a65aa976 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -1464,10 +1464,9 @@ retry:
     return NULL;
 }
 
-static int postcopy_temp_pages_setup(MigrationIncomingState *mis)
+static int postcopy_temp_pages_setup(MigrationIncomingState *mis, Error **errp)
 {
     PostcopyTmpPage *tmp_page;
-    int err;
     unsigned i, channels;
     void *temp_page;
 
@@ -1487,11 +1486,11 @@ static int postcopy_temp_pages_setup(MigrationIncomingState *mis)
         temp_page = mmap(NULL, mis->largest_page_size, PROT_READ | PROT_WRITE,
                          MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
         if (temp_page == MAP_FAILED) {
-            err = errno;
-            error_report("%s: Failed to map postcopy_tmp_pages[%d]: %s",
-                         __func__, i, strerror(err));
+            error_setg_errno(errp, errno,
+                             "%s: Failed to map postcopy_tmp_pages[%d]",
+                             __func__, i);
             /* Clean up will be done later */
-            return -err;
+            return -1;
         }
         tmp_page->tmp_huge_page = temp_page;
         /* Initialize default states for each tmp page */
@@ -1505,11 +1504,10 @@ static int postcopy_temp_pages_setup(MigrationIncomingState *mis)
                                        PROT_READ | PROT_WRITE,
                                        MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
     if (mis->postcopy_tmp_zero_page == MAP_FAILED) {
-        err = errno;
         mis->postcopy_tmp_zero_page = NULL;
-        error_report("%s: Failed to map large zero page %s",
-                     __func__, strerror(err));
-        return -err;
+        error_setg_errno(errp, errno, "%s: Failed to map large zero page",
+                         __func__);
+        return -1;
     }
 
     memset(mis->postcopy_tmp_zero_page, '\0', mis->largest_page_size);
@@ -1517,15 +1515,13 @@ static int postcopy_temp_pages_setup(MigrationIncomingState *mis)
     return 0;
 }
 
-int postcopy_ram_incoming_setup(MigrationIncomingState *mis)
+int postcopy_ram_incoming_setup(MigrationIncomingState *mis, Error **errp)
 {
-    Error *local_err = NULL;
-
     /* Open the fd for the kernel to give us userfaults */
     mis->userfault_fd = uffd_open(O_CLOEXEC | O_NONBLOCK);
     if (mis->userfault_fd == -1) {
-        error_report("%s: Failed to open userfault fd: %s", __func__,
-                     strerror(errno));
+        error_setg_errno(errp, errno, "%s: Failed to open userfault fd",
+                         __func__);
         return -1;
     }
 
@@ -1533,8 +1529,7 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis)
      * Although the host check already tested the API, we need to
      * do the check again as an ABI handshake on the new fd.
      */
-    if (!ufd_check_and_apply(mis->userfault_fd, mis, &local_err)) {
-        error_report_err(local_err);
+    if (!ufd_check_and_apply(mis->userfault_fd, mis, errp)) {
         return -1;
     }
 
@@ -1546,8 +1541,8 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis)
     /* Now an eventfd we use to tell the fault-thread to quit */
     mis->userfault_event_fd = eventfd(0, EFD_CLOEXEC);
     if (mis->userfault_event_fd == -1) {
-        error_report("%s: Opening userfault_event_fd: %s", __func__,
-                     strerror(errno));
+        error_setg_errno(errp, errno, "%s: Opening userfault_event_fd",
+                         __func__);
         close(mis->userfault_fd);
         return -1;
     }
@@ -1559,12 +1554,11 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis)
 
     /* Mark so that we get notified of accesses to unwritten areas */
     if (foreach_not_ignored_block(ram_block_enable_notify, mis)) {
-        error_report("ram_block_enable_notify failed");
+        error_setg(errp, "ram_block_enable_notify failed");
         return -1;
     }
 
-    if (postcopy_temp_pages_setup(mis)) {
-        /* Error dumped in the sub-function */
+    if (postcopy_temp_pages_setup(mis, errp)) {
         return -1;
     }
 
@@ -2201,9 +2195,8 @@ int postcopy_incoming_setup(MigrationIncomingState *mis, Error **errp)
      * shouldn't be doing anything yet so don't actually expect requests
      */
     if (migrate_postcopy_ram()) {
-        if (postcopy_ram_incoming_setup(mis)) {
+        if (postcopy_ram_incoming_setup(mis, errp)) {
             postcopy_ram_incoming_cleanup(mis);
-            error_setg(errp, "Failed to setup incoming postcopy RAM blocks");
             return -1;
         }
     }
diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h
index a080dd65a7..98d918713f 100644
--- a/migration/postcopy-ram.h
+++ b/migration/postcopy-ram.h
@@ -23,7 +23,7 @@ bool postcopy_ram_supported_by_host(MigrationIncomingState *mis,
  * Make all of RAM sensitive to accesses to areas that haven't yet been written
  * and wire up anything necessary to deal with it.
  */
-int postcopy_ram_incoming_setup(MigrationIncomingState *mis);
+int postcopy_ram_incoming_setup(MigrationIncomingState *mis, Error **errp);
 
 /*
  * Initialise postcopy-ram, setting the RAM to a state where we can go into
-- 
2.54.0