qemu-kvm/kvm-scsi-disk-Use-positive-return-value-for-status-in-dm.patch

From 1a0aa9bbdad63d72628002740410b8a28282a96e Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Wed, 31 Jul 2024 14:32:04 +0200
Subject: [PATCH 093/100] scsi-disk: Use positive return value for status in
 dma_readv/writev

RH-Author: Kevin Wolf <kwolf@redhat.com>
RH-MergeRequest: 261: scsi-block: Fix error handling with r/werror=stop
RH-Jira: RHEL-50000
RH-Acked-by: Hanna Czenczek <hreitz@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Commit: [1/4] a0b3e7bfd7b7059c0ec3706f2eb1698c1d430b08 (kmwolf/centos-qemu-kvm)

In some error cases, scsi_block_sgio_complete() never calls the passed
callback, but directly completes the request. This leads to bugs because
its error paths are not exact copies of what the callback would normally
do.

In preparation to fix this, allow passing positive return values to the
callbacks that represent the status code that should be used to complete
the request.

scsi_handle_rw_error() already handles positive values for its ret
parameter because scsi_block_sgio_complete() calls directly into it.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20240731123207.27636-2-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit cfe0880835cd364b590ffd27ef8dbd2ad8838bc5)
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 hw/scsi/scsi-disk.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index 4bd7af9d0c..bed2c8746c 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -62,6 +62,10 @@ OBJECT_DECLARE_TYPE(SCSIDiskState, SCSIDiskClass, SCSI_DISK_BASE)
 
 struct SCSIDiskClass {
     SCSIDeviceClass parent_class;
+    /*
+     * Callbacks receive ret == 0 for success. Errors are represented either as
+     * negative errno values, or as positive SAM status codes.
+     */
     DMAIOFunc       *dma_readv;
     DMAIOFunc       *dma_writev;
     bool            (*need_fua_emulation)(SCSICommand *cmd);
@@ -261,7 +265,7 @@ static bool scsi_disk_req_check_error(SCSIDiskReq *r, int ret, bool acct_failed)
         return true;
     }
 
-    if (ret < 0) {
+    if (ret != 0) {
         return scsi_handle_rw_error(r, ret, acct_failed);
     }
 
@@ -338,7 +342,7 @@ static void scsi_write_do_fua(SCSIDiskReq *r)
 static void scsi_dma_complete_noio(SCSIDiskReq *r, int ret)
 {
     assert(r->req.aiocb == NULL);
-    if (scsi_disk_req_check_error(r, ret, false)) {
+    if (scsi_disk_req_check_error(r, ret, ret > 0)) {
         goto done;
     }
 
@@ -363,9 +367,10 @@ static void scsi_dma_complete(void *opaque, int ret)
     assert(r->req.aiocb != NULL);
     r->req.aiocb = NULL;
 
+    /* ret > 0 is accounted for in scsi_disk_req_check_error() */
     if (ret < 0) {
         block_acct_failed(blk_get_stats(s->qdev.conf.blk), &r->acct);
-    } else {
+    } else if (ret == 0) {
         block_acct_done(blk_get_stats(s->qdev.conf.blk), &r->acct);
     }
     scsi_dma_complete_noio(r, ret);
@@ -381,7 +386,7 @@ static void scsi_read_complete_noio(SCSIDiskReq *r, int ret)
            qemu_get_current_aio_context());
 
     assert(r->req.aiocb == NULL);
-    if (scsi_disk_req_check_error(r, ret, false)) {
+    if (scsi_disk_req_check_error(r, ret, ret > 0)) {
         goto done;
     }
 
@@ -402,9 +407,10 @@ static void scsi_read_complete(void *opaque, int ret)
     assert(r->req.aiocb != NULL);
     r->req.aiocb = NULL;
 
+    /* ret > 0 is accounted for in scsi_disk_req_check_error() */
     if (ret < 0) {
         block_acct_failed(blk_get_stats(s->qdev.conf.blk), &r->acct);
-    } else {
+    } else if (ret == 0) {
         block_acct_done(blk_get_stats(s->qdev.conf.blk), &r->acct);
         trace_scsi_disk_read_complete(r->req.tag, r->qiov.size);
     }
@@ -512,7 +518,7 @@ static void scsi_write_complete_noio(SCSIDiskReq *r, int ret)
            qemu_get_current_aio_context());
 
     assert (r->req.aiocb == NULL);
-    if (scsi_disk_req_check_error(r, ret, false)) {
+    if (scsi_disk_req_check_error(r, ret, ret > 0)) {
         goto done;
     }
 
@@ -540,9 +546,10 @@ static void scsi_write_complete(void * opaque, int ret)
     assert (r->req.aiocb != NULL);
     r->req.aiocb = NULL;
 
+    /* ret > 0 is accounted for in scsi_disk_req_check_error() */
     if (ret < 0) {
         block_acct_failed(blk_get_stats(s->qdev.conf.blk), &r->acct);
-    } else {
+    } else if (ret == 0) {
         block_acct_done(blk_get_stats(s->qdev.conf.blk), &r->acct);
     }
     scsi_write_complete_noio(r, ret);
-- 
2.39.3