[Qemu-devel] [PATCH v3 26/44] 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 a flag
to qemu-io.  To be useful, the device has to be opened with
'qemu-io -d unmap' (or the just-added 'open -u' subcommand).

Signed-off-by: Eric Blake <eblake@redhat.com>
---
 qemu-io-cmds.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
index 1e444cc..ca23459 100644
--- a/qemu-io-cmds.c
+++ b/qemu-io-cmds.c
@@ -454,6 +454,7 @@ typedef struct {
     int64_t count;
     int64_t *total;
     bool fua;
+    bool unmap;
     int ret;
     bool done;
 } CoWriteZeroes;
@@ -464,7 +465,8 @@ static void coroutine_fn co_write_zeroes_entry(void *opaque)

     data->ret = blk_co_write_zeroes(data->blk, data->offset / BDRV_SECTOR_SIZE,
                                     data->count / BDRV_SECTOR_SIZE,
-                                    data->fua ? BDRV_REQ_FUA : 0);
+                                    (data->fua ? BDRV_REQ_FUA : 0) |
+                                    (data->unmap ? BDRV_REQ_MAY_UNMAP : 0));
     data->done = true;
     if (data->ret < 0) {
         *data->total = data->ret;
@@ -475,7 +477,7 @@ static void coroutine_fn co_write_zeroes_entry(void *opaque)
 }

 static int do_co_write_zeroes(BlockBackend *blk, int64_t offset, int64_t count,
-                              bool fua, int64_t *total)
+                              bool fua, bool unmap, int64_t *total)
 {
     Coroutine *co;
     CoWriteZeroes data = {
@@ -484,6 +486,7 @@ static int do_co_write_zeroes(BlockBackend *blk, int64_t offset, int64_t count,
         .count  = count,
         .total  = total,
         .fua    = fua,
+        .unmap  = unmap,
         .done   = false,
     };

@@ -959,6 +962,7 @@ 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");
 }
@@ -971,7 +975,7 @@ 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,
 };
@@ -980,7 +984,7 @@ static int write_f(BlockBackend *blk, int argc, char **argv)
 {
     struct timeval t1, t2;
     int Cflag = 0, qflag = 0, bflag = 0, Pflag = 0, zflag = 0;
-    int cflag = 0, fflag = 0;
+    int cflag = 0, fflag = 0, uflag = 0;
     int c, cnt;
     char *buf = NULL;
     int64_t offset;
@@ -989,7 +993,7 @@ 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 = 1;
@@ -1016,6 +1020,9 @@ static int write_f(BlockBackend *blk, int argc, char **argv)
         case 'q':
             qflag = 1;
             break;
+        case 'u':
+            uflag = 1;
+            break;
         case 'z':
             zflag = 1;
             break;
@@ -1038,6 +1045,11 @@ static int write_f(BlockBackend *blk, int argc, char **argv)
         return 0;
     }

+    if (uflag && !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;
@@ -1082,7 +1094,7 @@ static int write_f(BlockBackend *blk, int argc, char **argv)
     if (bflag) {
         cnt = do_save_vmstate(blk, buf, offset, count, &total);
     } else if (zflag) {
-        cnt = do_co_write_zeroes(blk, offset, count, fflag, &total);
+        cnt = do_co_write_zeroes(blk, offset, count, fflag, uflag, &total);
     } else if (cflag) {
         cnt = do_write_compressed(blk, buf, offset, count, &total);
     } else {
-- 
2.5.5