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Blame SOURCES/kvm-qemu-img-Resolve-relative-backing-paths-in-rebase.patch

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From 68af7bd1c3085fb25f50a7ad8cada0c33dbba748 Mon Sep 17 00:00:00 2001
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From: Max Reitz <mreitz@redhat.com>
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Date: Mon, 18 Jun 2018 17:48:32 +0200
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Subject: [PATCH 071/268] qemu-img: Resolve relative backing paths in rebase
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RH-Author: Max Reitz <mreitz@redhat.com>
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Message-id: <20180618174833.19439-2-mreitz@redhat.com>
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Patchwork-id: 80790
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O-Subject: [RHV-7.6 qemu-kvm-rhev PATCH 1/2] qemu-img: Resolve relative backing paths in rebase
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Bugzilla: 1569835
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RH-Acked-by: John Snow <jsnow@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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Currently, rebase interprets a relative path for the new backing image
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as follows:
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(1) Open the new backing image with the given relative path (thus relative to
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    qemu-img's working directory).
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(2) Write it directly into the overlay's backing path field (thus
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    relative to the overlay).
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If the overlay is not in qemu-img's working directory, both will be
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different interpretations, which may either lead to an error somewhere
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(either rebase fails because it cannot open the new backing image, or
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your overlay becomes unusable because its backing path does not point to
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a file), or, even worse, it may result in your rebase being performed
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for a different backing file than what your overlay will point to after
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the rebase.
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Fix this by interpreting the target backing path as relative to the
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overlay, like qemu-img does everywhere else.
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Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1569835
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Cc: qemu-stable@nongnu.org
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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Message-id: 20180509182002.8044-2-mreitz@redhat.com
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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(cherry picked from commit d16699b64671466b42079c45b89127aeea1ca565)
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 qemu-img.c | 23 ++++++++++++++++++++++-
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 1 file changed, 22 insertions(+), 1 deletion(-)
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diff --git a/qemu-img.c b/qemu-img.c
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index 4bcf157..76d6e47 100644
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--- a/qemu-img.c
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+++ b/qemu-img.c
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@@ -3202,6 +3202,9 @@ static int img_rebase(int argc, char **argv)
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         }
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         if (out_baseimg[0]) {
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+            const char *overlay_filename;
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+            char *out_real_path;
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+
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             options = qdict_new();
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             if (out_basefmt) {
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                 qdict_put_str(options, "driver", out_basefmt);
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@@ -3210,8 +3213,26 @@ static int img_rebase(int argc, char **argv)
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                 qdict_put_bool(options, BDRV_OPT_FORCE_SHARE, true);
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             }
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-            blk_new_backing = blk_new_open(out_baseimg, NULL,
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+            overlay_filename = bs->exact_filename[0] ? bs->exact_filename
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+                                                     : bs->filename;
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+            out_real_path = g_malloc(PATH_MAX);
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+
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+            bdrv_get_full_backing_filename_from_filename(overlay_filename,
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+                                                         out_baseimg,
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+                                                         out_real_path,
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+                                                         PATH_MAX,
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+                                                         &local_err);
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+            if (local_err) {
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+                error_reportf_err(local_err,
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+                                  "Could not resolve backing filename: ");
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+                ret = -1;
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+                g_free(out_real_path);
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+                goto out;
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+            }
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+
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+            blk_new_backing = blk_new_open(out_real_path, NULL,
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                                            options, src_flags, &local_err);
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+            g_free(out_real_path);
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             if (!blk_new_backing) {
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                 error_reportf_err(local_err,
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                                   "Could not open new backing file '%s': ",
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-- 
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1.8.3.1
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