pve-qemu-qoup/debian/patches/pve/0025-qemu-img-dd-add-osize-and-read-from-to-stdin-stdout.patch

From 3bd6a30a92ecb420bac469ec977fbcc0ad918d1c Mon Sep 17 00:00:00 2001
From: Wolfgang Bumiller <w.bumiller@proxmox.com>
Date: Fri, 23 Jun 2017 12:01:43 +0200
Subject: [PATCH 25/28] qemu-img dd: add osize and read from/to stdin/stdout

Neither convert nor dd were previously able to write to or
read from a pipe. Particularly serializing an image file
into a raw stream or vice versa can be useful, but using
`qemu-img convert -f qcow2 -O raw foo.qcow2 /dev/stdout` in
a pipe will fail trying to seek.

While dd and convert have overlapping use cases, `dd` is a
simple read/write loop while convert is much more
sophisticated and has ways to dealing with holes and blocks
of zeroes.
Since these typically can't be detected in pipes via
SEEK_DATA/HOLE or skipped while writing, dd seems to be the
better choice for implementing stdin/stdout streams.

This patch causes "if" and "of" to default to stdin and
stdout respectively, allowing only the "raw" format to be
used in these cases.
Since the input can now be a pipe we have no way of
detecting the size of the output image to create. Since we
also want to support images with a size not matching the
dd command's "bs" parameter (which, together with "count"
could be used to calculate the desired size, and is already
used to limit it), the "osize" option is added to explicitly
override the output file's size.

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
---
 qemu-img-cmds.hx |   4 +-
 qemu-img.c       | 176 +++++++++++++++++++++++++++++++++++--------------------
 2 files changed, 115 insertions(+), 65 deletions(-)

diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx
index 8ac78222af..16bee83987 100644
--- a/qemu-img-cmds.hx
+++ b/qemu-img-cmds.hx
@@ -46,9 +46,9 @@ STEXI
 ETEXI
 
 DEF("dd", img_dd,
-    "dd [--image-opts] [-f fmt] [-O output_fmt] [bs=block_size] [count=blocks] [skip=blocks] if=input of=output")
+    "dd [--image-opts] [-f fmt] [-O output_fmt] [bs=block_size] [count=blocks] [skip=blocks] [osize=output_size] [if=input] [of=output]")
 STEXI
-@item dd [--image-opts] [-f @var{fmt}] [-O @var{output_fmt}] [bs=@var{block_size}] [count=@var{blocks}] [skip=@var{blocks}] if=@var{input} of=@var{output}
+@item dd [--image-opts] [-f @var{fmt}] [-O @var{output_fmt}] [bs=@var{block_size}] [count=@var{blocks}] [skip=@var{blocks}] [osize=output_size] [if=@var{input}] [of=@var{output}]
 ETEXI
 
 DEF("info", img_info,
diff --git a/qemu-img.c b/qemu-img.c
index 4f7f458dd2..b9d1ef7bb8 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -4035,10 +4035,12 @@ out:
 #define C_IF      04
 #define C_OF      010
 #define C_SKIP    020
+#define C_OSIZE   040
 
 struct DdInfo {
     unsigned int flags;
     int64_t count;
+    int64_t osize;
 };
 
 struct DdIo {
@@ -4117,6 +4119,20 @@ static int img_dd_skip(const char *arg,
     return 0;
 }
 
+static int img_dd_osize(const char *arg,
+                        struct DdIo *in, struct DdIo *out,
+                        struct DdInfo *dd)
+{
+    dd->osize = cvtnum(arg);
+
+    if (dd->osize < 0) {
+        error_report("invalid number: '%s'", arg);
+        return 1;
+    }
+
+    return 0;
+}
+
 static int img_dd(int argc, char **argv)
 {
     int ret = 0;
@@ -4156,6 +4172,7 @@ static int img_dd(int argc, char **argv)
         { "if", img_dd_if, C_IF },
         { "of", img_dd_of, C_OF },
         { "skip", img_dd_skip, C_SKIP },
+        { "osize", img_dd_osize, C_OSIZE },
         { NULL, NULL, 0 }
     };
     const struct option long_options[] = {
@@ -4223,84 +4240,106 @@ static int img_dd(int argc, char **argv)
         arg = NULL;
     }
 
-    if (!(dd.flags & C_IF && dd.flags & C_OF)) {
-        error_report("Must specify both input and output files");
+    if (!(dd.flags & C_IF) && (!fmt || strcmp(fmt, "raw") != 0)) {
+        error_report("Input format must be raw when readin from stdin");
         ret = -1;
         goto out;
     }
-    blk1 = img_open(image_opts, in.filename, fmt, 0, false, false);
-
-    if (!blk1) {
+    if (!(dd.flags & C_OF) && strcmp(out_fmt, "raw") != 0) {
+        error_report("Output format must be raw when writing to stdout");
         ret = -1;
         goto out;
     }
+    if (dd.flags & C_IF) {
+        blk1 = img_open(image_opts, in.filename, fmt, 0, false, false);
 
-    drv = bdrv_find_format(out_fmt);
-    if (!drv) {
-        error_report("Unknown file format");
-        ret = -1;
-        goto out;
-    }
-    proto_drv = bdrv_find_protocol(out.filename, true, &local_err);
-
-    if (!proto_drv) {
-        error_report_err(local_err);
-        ret = -1;
-        goto out;
-    }
-    if (!drv->create_opts) {
-        error_report("Format driver '%s' does not support image creation",
-                     drv->format_name);
-        ret = -1;
-        goto out;
-    }
-    if (!proto_drv->create_opts) {
-        error_report("Protocol driver '%s' does not support image creation",
-                     proto_drv->format_name);
-        ret = -1;
-        goto out;
+        if (!blk1) {
+            ret = -1;
+            goto out;
+        }
     }
-    create_opts = qemu_opts_append(create_opts, drv->create_opts);
-    create_opts = qemu_opts_append(create_opts, proto_drv->create_opts);
-
-    opts = qemu_opts_create(create_opts, NULL, 0, &error_abort);
 
-    size = blk_getlength(blk1);
-    if (size < 0) {
-        error_report("Failed to get size for '%s'", in.filename);
+    if (dd.flags & C_OSIZE) {
+        size = dd.osize;
+    } else if (dd.flags & C_IF) {
+        size = blk_getlength(blk1);
+        if (size < 0) {
+            error_report("Failed to get size for '%s'", in.filename);
+            ret = -1;
+            goto out;
+        }
+    } else if (dd.flags & C_COUNT) {
+        size = dd.count * in.bsz;
+    } else {
+        error_report("Output size must be known when reading from stdin");
         ret = -1;
         goto out;
     }
 
-    if (dd.flags & C_COUNT && dd.count <= INT64_MAX / in.bsz &&
+    if (!(dd.flags & C_OSIZE) && dd.flags & C_COUNT && dd.count <= INT64_MAX / in.bsz &&
         dd.count * in.bsz < size) {
         size = dd.count * in.bsz;
     }
 
-    /* Overflow means the specified offset is beyond input image's size */
-    if (dd.flags & C_SKIP && (in.offset > INT64_MAX / in.bsz ||
-                              size < in.bsz * in.offset)) {
-        qemu_opt_set_number(opts, BLOCK_OPT_SIZE, 0, &error_abort);
-    } else {
-        qemu_opt_set_number(opts, BLOCK_OPT_SIZE,
-                            size - in.bsz * in.offset, &error_abort);
-    }
 
-    ret = bdrv_create(drv, out.filename, opts, &local_err);
-    if (ret < 0) {
-        error_reportf_err(local_err,
-                          "%s: error while creating output image: ",
-                          out.filename);
-        ret = -1;
-        goto out;
-    }
+    if (dd.flags & C_OF) {
+        drv = bdrv_find_format(out_fmt);
+        if (!drv) {
+            error_report("Unknown file format");
+            ret = -1;
+            goto out;
+        }
+        proto_drv = bdrv_find_protocol(out.filename, true, &local_err);
+
+        if (!proto_drv) {
+            error_report_err(local_err);
+            ret = -1;
+            goto out;
+        }
+        if (!drv->create_opts) {
+            error_report("Format driver '%s' does not support image creation",
+                         drv->format_name);
+            ret = -1;
+            goto out;
+        }
+        if (!proto_drv->create_opts) {
+            error_report("Protocol driver '%s' does not support image creation",
+                         proto_drv->format_name);
+            ret = -1;
+            goto out;
+        }
+        create_opts = qemu_opts_append(create_opts, drv->create_opts);
+        create_opts = qemu_opts_append(create_opts, proto_drv->create_opts);
 
-    blk2 = img_open(image_opts, out.filename, out_fmt, BDRV_O_RDWR,
-                    false, false);
+        opts = qemu_opts_create(create_opts, NULL, 0, &error_abort);
 
-    if (!blk2) {
-        ret = -1;
-        goto out;
+        /* Overflow means the specified offset is beyond input image's size */
+        if (dd.flags & C_OSIZE) {
+            qemu_opt_set_number(opts, BLOCK_OPT_SIZE, size, &error_abort);
+        } else if (dd.flags & C_SKIP && (in.offset > INT64_MAX / in.bsz ||
+                                         size < in.bsz * in.offset)) {
+            qemu_opt_set_number(opts, BLOCK_OPT_SIZE, 0, &error_abort);
+        } else {
+            qemu_opt_set_number(opts, BLOCK_OPT_SIZE,
+                                size - in.bsz * in.offset, &error_abort);
+        }
+
+        ret = bdrv_create(drv, out.filename, opts, &local_err);
+        if (ret < 0) {
+            error_reportf_err(local_err,
+                              "%s: error while creating output image: ",
+                              out.filename);
+            ret = -1;
+            goto out;
+        }
+
+        blk2 = img_open(image_opts, out.filename, out_fmt, BDRV_O_RDWR,
+                        false, false);
+
+        if (!blk2) {
+            ret = -1;
+            goto out;
+        }
     }
 
     if (dd.flags & C_SKIP && (in.offset > INT64_MAX / in.bsz ||
@@ -4318,11 +4357,18 @@ static int img_dd(int argc, char **argv)
 
     for (out_pos = 0; in_pos < size; block_count++) {
         int in_ret, out_ret;
+        size_t in_bsz = in_pos + in.bsz > size ? size - in_pos : in.bsz;
 
-        if (in_pos + in.bsz > size) {
-            in_ret = blk_pread(blk1, in_pos, in.buf, size - in_pos);
+        if (blk1) {
+            in_ret = blk_pread(blk1, in_pos, in.buf, in_bsz);
         } else {
-            in_ret = blk_pread(blk1, in_pos, in.buf, in.bsz);
+            in_ret = read(STDIN_FILENO, in.buf, in_bsz);
+            if (in_ret == 0) {
+                /* early EOF is considered an error */
+                error_report("Input ended unexpectedly");
+                ret = -1;
+                goto out;
+            }
         }
         if (in_ret < 0) {
             error_report("error while reading from input image file: %s",
@@ -4332,9 +4378,13 @@ static int img_dd(int argc, char **argv)
         }
         in_pos += in_ret;
 
-        out_ret = blk_pwrite(blk2, out_pos, in.buf, in_ret, 0);
+        if (blk2) {
+            out_ret = blk_pwrite(blk2, out_pos, in.buf, in_ret, 0);
+        } else {
+            out_ret = write(STDOUT_FILENO, in.buf, in_ret);
+        }
 
-        if (out_ret < 0) {
+        if (out_ret != in_ret) {
             error_report("error while writing to output image file: %s",
                          strerror(-out_ret));
             ret = -1;
-- 
2.11.0