[Qemu-devel] [PATCH v5 6/6] qemu-io: Add 'write -z -u' to test MAY_UNMAP flag

[Eric Blake <eblake@redhat.com>]

Make it easier to control whether the BDRV_REQ_MAY_UNMAP flag
can be passed through a write_zeroes command, by adding the '-u'
flag to qemu-io 'write -z' and 'aio_write -z'.  To be useful,
the device has to be opened with BDRV_O_UNMAP (done by default
in qemu-io, but can be made explicit with '-d unmap').

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>

---
v5: tweak commit message for rebase conflict resolution
---
 qemu-io-cmds.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
index 17f408d..83de5f9 100644
--- a/qemu-io-cmds.c
+++ b/qemu-io-cmds.c
@@ -943,6 +943,7 @@ static void write_help(void)
 " -P, -- use different pattern to fill file\n"
 " -C, -- report statistics in a machine parsable format\n"
 " -q, -- quiet mode, do not show I/O statistics\n"
+" -u, -- with -z, allow unmapping\n"
 " -z, -- write zeroes using blk_co_write_zeroes\n"
 "\n");
 }
@@ -955,7 +956,7 @@ static const cmdinfo_t write_cmd = {
     .cfunc      = write_f,
     .argmin     = 2,
     .argmax     = -1,
-    .args       = "[-bcCfqz] [-P pattern] off len",
+    .args       = "[-bcCfquz] [-P pattern] off len",
     .oneline    = "writes a number of bytes at a specified offset",
     .help       = write_help,
 };
@@ -974,7 +975,7 @@ static int write_f(BlockBackend *blk, int argc, char **argv)
     int64_t total = 0;
     int pattern = 0xcd;

-    while ((c = getopt(argc, argv, "bcCfpP:qz")) != -1) {
+    while ((c = getopt(argc, argv, "bcCfpP:quz")) != -1) {
         switch (c) {
         case 'b':
             bflag = true;
@@ -1001,6 +1002,9 @@ static int write_f(BlockBackend *blk, int argc, char **argv)
         case 'q':
             qflag = true;
             break;
+        case 'u':
+            flags |= BDRV_REQ_MAY_UNMAP;
+            break;
         case 'z':
             zflag = true;
             break;
@@ -1023,6 +1027,11 @@ static int write_f(BlockBackend *blk, int argc, char **argv)
         return 0;
     }

+    if ((flags & BDRV_REQ_MAY_UNMAP) && !zflag) {
+        printf("-u requires -z to be specified\n");
+        return 0;
+    }
+
     if (zflag && Pflag) {
         printf("-z and -P cannot be specified at the same time\n");
         return 0;
@@ -1561,6 +1570,7 @@ static void aio_write_help(void)
 " -C, -- report statistics in a machine parsable format\n"
 " -f, -- use Force Unit Access semantics\n"
 " -q, -- quiet mode, do not show I/O statistics\n"
+" -u, -- with -z, allow unmapping\n"
 " -z, -- write zeroes using blk_aio_write_zeroes\n"
 "\n");
 }
@@ -1572,7 +1582,7 @@ static const cmdinfo_t aio_write_cmd = {
     .cfunc      = aio_write_f,
     .argmin     = 2,
     .argmax     = -1,
-    .args       = "[-Cfqz] [-P pattern] off len [len..]",
+    .args       = "[-Cfquz] [-P pattern] off len [len..]",
     .oneline    = "asynchronously writes a number of bytes",
     .help       = aio_write_help,
 };
@@ -1596,6 +1606,9 @@ static int aio_write_f(BlockBackend *blk, int argc, char **argv)
         case 'q':
             ctx->qflag = true;
             break;
+        case 'u':
+            flags |= BDRV_REQ_MAY_UNMAP;
+            break;
         case 'P':
             pattern = parse_pattern(optarg);
             if (pattern < 0) {
@@ -1623,6 +1636,11 @@ static int aio_write_f(BlockBackend *blk, int argc, char **argv)
         return 0;
     }

+    if ((flags & BDRV_REQ_MAY_UNMAP) && !ctx->zflag) {
+        printf("-u requires -z to be specified\n");
+        return 0;
+    }
+
     if (ctx->zflag && ctx->Pflag) {
         printf("-z and -P cannot be specified at the same time\n");
         g_free(ctx);
-- 
2.5.5