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From 8aff951dc5acb2965131e43e10b1cd9fce17992e Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Thu, 10 Jan 2019 12:44:36 +0000
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Subject: [PATCH 06/14] file-posix: Support auto-read-only option
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <20190110124442.30132-7-kwolf@redhat.com>
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Patchwork-id: 83955
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O-Subject: [RHEL-8.0 qemu-kvm PATCH 06/12] file-posix: Support auto-read-only option
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Bugzilla: 1644996
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Eric Blake <eblake@redhat.com>
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If read-only=off, but auto-read-only=on is given, open the file
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read-write if we have the permissions, but instead of erroring out for
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read-only files, just degrade to read-only.
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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(cherry picked from commit 64107dc044a54ebe46348ac0fe87584be2eb3e81)
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 block/file-posix.c | 19 ++++++++++++++++---
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 1 file changed, 16 insertions(+), 3 deletions(-)
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diff --git a/block/file-posix.c b/block/file-posix.c
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index c12cdb7..7e6869d 100644
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--- a/block/file-posix.c
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+++ b/block/file-posix.c
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@@ -517,9 +517,22 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,
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     s->fd = -1;
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     fd = qemu_open(filename, s->open_flags, 0644);
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-    if (fd < 0) {
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-        ret = -errno;
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-        error_setg_errno(errp, errno, "Could not open '%s'", filename);
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+    ret = fd < 0 ? -errno : 0;
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+
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+    if (ret == -EACCES || ret == -EROFS) {
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+        /* Try to degrade to read-only, but if it doesn't work, still use the
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+         * normal error message. */
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+        if (bdrv_apply_auto_read_only(bs, NULL, NULL) == 0) {
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+            bdrv_flags &= ~BDRV_O_RDWR;
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+            raw_parse_flags(bdrv_flags, &s->open_flags);
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+            assert(!(s->open_flags & O_CREAT));
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+            fd = qemu_open(filename, s->open_flags);
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+            ret = fd < 0 ? -errno : 0;
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+        }
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+    }
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+
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+    if (ret < 0) {
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+        error_setg_errno(errp, -ret, "Could not open '%s'", filename);
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         if (ret == -EROFS) {
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             ret = -EACCES;
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         }
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-- 
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1.8.3.1
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