[Qemu-devel] [PATCH] qemu-io: Add discard command

[Stefan Hajnoczi]

discard [-Cq] off len -- discards a number of bytes at a specified
offset

 discards a range of bytes from the given offset

 Example:
 'discard 512 1k' - discards 1 kilobyte from 512 bytes into the file

 Discards a segment of the currently open file.
 -C, -- report statistics in a machine parsable format
 -q, -- quite mode, do not show I/O statistics

Signed-off-by: Stefan Hajnoczi <address@hidden>
---
 qemu-io.c |   88 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 88 insertions(+), 0 deletions(-)

diff --git a/qemu-io.c b/qemu-io.c
index ff353eb..9de5361 100644
--- a/qemu-io.c
+++ b/qemu-io.c
@@ -1394,6 +1394,93 @@ static const cmdinfo_t info_cmd = {
        .oneline        = "prints information about the current file",
 };
 
+static void
+discard_help(void)
+{
+       printf(
+"\n"
+" discards a range of bytes from the given offset\n"
+"\n"
+" Example:\n"
+" 'discard 512 1k' - discards 1 kilobyte from 512 bytes into the file\n"
+"\n"
+" Discards a segment of the currently open file.\n"
+" -C, -- report statistics in a machine parsable format\n"
+" -q, -- quite mode, do not show I/O statistics\n"
+"\n");
+}
+
+static int discard_f(int argc, char **argv);
+
+static const cmdinfo_t discard_cmd = {
+       .name           = "discard",
+       .altname        = "d",
+       .cfunc          = discard_f,
+       .argmin         = 2,
+       .argmax         = -1,
+       .args           = "[-Cq] off len",
+       .oneline        = "discards a number of bytes at a specified offset",
+       .help           = discard_help,
+};
+
+static int
+discard_f(int argc, char **argv)
+{
+       struct timeval t1, t2;
+       int Cflag = 0, qflag = 0;
+       int c, ret;
+       int64_t offset;
+       int count;
+
+       while ((c = getopt(argc, argv, "Cq")) != EOF) {
+               switch (c) {
+               case 'C':
+                       Cflag = 1;
+                       break;
+               case 'q':
+                       qflag = 1;
+                       break;
+               default:
+                       return command_usage(&discard_cmd);
+               }
+       }
+
+       if (optind != argc - 2) {
+               return command_usage(&discard_cmd);
+       }
+
+       offset = cvtnum(argv[optind]);
+       if (offset < 0) {
+               printf("non-numeric length argument -- %s\n", argv[optind]);
+               return 0;
+       }
+
+       optind++;
+       count = cvtnum(argv[optind]);
+       if (count < 0) {
+               printf("non-numeric length argument -- %s\n", argv[optind]);
+               return 0;
+       }
+
+       gettimeofday(&t1, NULL);
+       ret = bdrv_discard(bs, offset, count);
+       gettimeofday(&t2, NULL);
+
+       if (ret < 0) {
+               printf("discard failed: %s\n", strerror(-ret));
+               goto out;
+       }
+
+       /* Finally, report back -- -C gives a parsable format */
+       if (!qflag) {
+               t2 = tsub(t2, t1);
+               print_report("discard", &t2, offset, count, count, 1, Cflag);
+       }
+
+out:
+       return 0;
+}
+
 static int
 alloc_f(int argc, char **argv)
 {
@@ -1717,6 +1804,7 @@ int main(int argc, char **argv)
        add_command(&truncate_cmd);
        add_command(&length_cmd);
        add_command(&info_cmd);
+       add_command(&discard_cmd);
        add_command(&alloc_cmd);
        add_command(&map_cmd);
 
-- 
1.7.2.3