[Qemu-devel] [PATCH RFC 0/3] block: Backdoor to skip image locking in qemu-io/qemu-img

[Qemu-devel] [PATCH RFC 0/3] block: Backdoor to skip image locking in qemu-io/qemu-img

[Fam Zheng]

Hi Kevin,

This tries to capture your idea to add a explicit command option in qemu-io and
qemu-img for user to specify "expect inconsistent data when reading image".
It's stored as a BDRV_O_ flag internally, I don't know if there is a cleaner
way or not.

It's depended on by image locking series because several test cases need to be
updated to use this flag.

Fam

Fam Zheng (3):
  block: Introduce BDRV_O_UNSAFE_READ
  qemu-img: Add --unsafe-read option to subcommands
  qemu-io: Add --unsafe-read option

 block/block-backend.c |   2 +-
 include/block/block.h |   1 +
 qemu-img.c            | 148 ++++++++++++++++++++++++++++++++++++++------------
 qemu-io.c             |  28 +++++++---
 4 files changed, 137 insertions(+), 42 deletions(-)

-- 
2.9.3

[Qemu-devel] [PATCH RFC 1/3] block: Introduce BDRV_O_UNSAFE_READ

[Fam Zheng]

This flag clears out the "consistent read" permission that blk_new_open
requests.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 block/block-backend.c | 2 +-
 include/block/block.h | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/block-backend.c b/block/block-backend.c
index 5742c09..99428ee 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -197,7 +197,7 @@ BlockBackend *blk_new_open(const char *filename, const char *reference,
      * caller of blk_new_open() doesn't make use of the permissions, but they
      * shouldn't hurt either. We can still share everything here because the
      * guest devices will add their own blockers if they can't share. */
-    perm = BLK_PERM_CONSISTENT_READ;
+    perm = flags & BDRV_O_UNSAFE_READ ? 0 : BLK_PERM_CONSISTENT_READ;
     if (flags & BDRV_O_RDWR) {
         perm |= BLK_PERM_WRITE;
     }
diff --git a/include/block/block.h b/include/block/block.h
index 5149260..d43b563 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -98,6 +98,7 @@ typedef struct HDGeometry {
                                       select an appropriate protocol driver,
                                       ignoring the format layer */
 #define BDRV_O_NO_IO       0x10000 /* don't initialize for I/O */
+#define BDRV_O_UNSAFE_READ 0x20000 /* don't require consistent read */
 
 #define BDRV_O_CACHE_MASK  (BDRV_O_NOCACHE | BDRV_O_NO_FLUSH)
 
-- 
2.9.3

[Qemu-devel] [PATCH RFC 2/3] qemu-img: Add --unsafe-read option to subcommands

[Fam Zheng]

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 qemu-img.c | 148 +++++++++++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 114 insertions(+), 34 deletions(-)

diff --git a/qemu-img.c b/qemu-img.c
index 98b836b..3aaa254 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -273,12 +273,15 @@ static int img_open_password(BlockBackend *blk, const char *filename,
 
 static BlockBackend *img_open_opts(const char *optstr,
                                    QemuOpts *opts, int flags, bool writethrough,
-                                   bool quiet)
+                                   bool quiet, bool unsafe)
 {
     QDict *options;
     Error *local_err = NULL;
     BlockBackend *blk;
     options = qemu_opts_to_qdict(opts, NULL);
+    if (unsafe) {
+        flags |= BDRV_O_UNSAFE_READ;
+    }
     blk = blk_new_open(NULL, NULL, options, flags, &local_err);
     if (!blk) {
         error_reportf_err(local_err, "Could not open '%s': ", optstr);
@@ -295,7 +298,7 @@ static BlockBackend *img_open_opts(const char *optstr,
 
 static BlockBackend *img_open_file(const char *filename,
                                    const char *fmt, int flags,
-                                   bool writethrough, bool quiet)
+                                   bool writethrough, bool quiet, bool unsafe)
 {
     BlockBackend *blk;
     Error *local_err = NULL;
@@ -306,6 +309,9 @@ static BlockBackend *img_open_file(const char *filename,
         qdict_put(options, "driver", qstring_from_str(fmt));
     }
 
+    if (unsafe) {
+        flags |= BDRV_O_UNSAFE_READ;
+    }
     blk = blk_new_open(filename, NULL, options, flags, &local_err);
     if (!blk) {
         error_reportf_err(local_err, "Could not open '%s': ", filename);
@@ -324,7 +330,7 @@ static BlockBackend *img_open_file(const char *filename,
 static BlockBackend *img_open(bool image_opts,
                               const char *filename,
                               const char *fmt, int flags, bool writethrough,
-                              bool quiet)
+                              bool quiet, bool unsafe)
 {
     BlockBackend *blk;
     if (image_opts) {
@@ -338,9 +344,9 @@ static BlockBackend *img_open(bool image_opts,
         if (!opts) {
             return NULL;
         }
-        blk = img_open_opts(filename, opts, flags, writethrough, quiet);
+        blk = img_open_opts(filename, opts, flags, writethrough, quiet, unsafe);
     } else {
-        blk = img_open_file(filename, fmt, flags, writethrough, quiet);
+        blk = img_open_file(filename, fmt, flags, writethrough, quiet, unsafe);
     }
     return blk;
 }
@@ -635,6 +641,7 @@ static int img_check(int argc, char **argv)
     ImageCheck *check;
     bool quiet = false;
     bool image_opts = false;
+    bool unsafe_read = false;
 
     fmt = NULL;
     output = NULL;
@@ -649,9 +656,10 @@ static int img_check(int argc, char **argv)
             {"output", required_argument, 0, OPTION_OUTPUT},
             {"object", required_argument, 0, OPTION_OBJECT},
             {"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
+            {"unsafe-read", no_argument, 0, 'U'},
             {0, 0, 0, 0}
         };
-        c = getopt_long(argc, argv, "hf:r:T:q",
+        c = getopt_long(argc, argv, "hf:r:T:qU",
                         long_options, &option_index);
         if (c == -1) {
             break;
@@ -685,6 +693,9 @@ static int img_check(int argc, char **argv)
         case 'q':
             quiet = true;
             break;
+        case 'U':
+            unsafe_read = true;
+            break;
         case OPTION_OBJECT: {
             QemuOpts *opts;
             opts = qemu_opts_parse_noisily(&qemu_object_opts,
@@ -724,7 +735,8 @@ static int img_check(int argc, char **argv)
         return 1;
     }
 
-    blk = img_open(image_opts, filename, fmt, flags, writethrough, quiet);
+    blk = img_open(image_opts, filename, fmt, flags, writethrough, quiet,
+                   unsafe_read);
     if (!blk) {
         return 1;
     }
@@ -844,6 +856,7 @@ static int img_commit(int argc, char **argv)
     CommonBlockJobCBInfo cbi;
     bool image_opts = false;
     AioContext *aio_context;
+    bool unsafe_read = false;
 
     fmt = NULL;
     cache = BDRV_DEFAULT_CACHE;
@@ -853,9 +866,10 @@ static int img_commit(int argc, char **argv)
             {"help", no_argument, 0, 'h'},
             {"object", required_argument, 0, OPTION_OBJECT},
             {"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
+            {"unsafe-read", no_argument, 0, 'U'},
             {0, 0, 0, 0}
         };
-        c = getopt_long(argc, argv, "f:ht:b:dpq",
+        c = getopt_long(argc, argv, "f:ht:b:dpqU",
                         long_options, NULL);
         if (c == -1) {
             break;
@@ -885,6 +899,9 @@ static int img_commit(int argc, char **argv)
         case 'q':
             quiet = true;
             break;
+        case 'U':
+            unsafe_read = true;
+            break;
         case OPTION_OBJECT: {
             QemuOpts *opts;
             opts = qemu_opts_parse_noisily(&qemu_object_opts,
@@ -922,7 +939,8 @@ static int img_commit(int argc, char **argv)
         return 1;
     }
 
-    blk = img_open(image_opts, filename, fmt, flags, writethrough, quiet);
+    blk = img_open(image_opts, filename, fmt, flags, writethrough, quiet,
+                   unsafe_read);
     if (!blk) {
         return 1;
     }
@@ -1181,6 +1199,7 @@ static int img_compare(int argc, char **argv)
     int c, pnum;
     uint64_t progress_base;
     bool image_opts = false;
+    bool unsafe_read = false;
 
     cache = BDRV_DEFAULT_CACHE;
     for (;;) {
@@ -1188,9 +1207,10 @@ static int img_compare(int argc, char **argv)
             {"help", no_argument, 0, 'h'},
             {"object", required_argument, 0, OPTION_OBJECT},
             {"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
+            {"unsafe-read", no_argument, 0, 'U'},
             {0, 0, 0, 0}
         };
-        c = getopt_long(argc, argv, "hf:F:T:pqs",
+        c = getopt_long(argc, argv, "hf:F:T:pqsU",
                         long_options, NULL);
         if (c == -1) {
             break;
@@ -1218,6 +1238,9 @@ static int img_compare(int argc, char **argv)
         case 's':
             strict = true;
             break;
+        case 'U':
+            unsafe_read = true;
+            break;
         case OPTION_OBJECT: {
             QemuOpts *opts;
             opts = qemu_opts_parse_noisily(&qemu_object_opts,
@@ -1263,13 +1286,15 @@ static int img_compare(int argc, char **argv)
         goto out3;
     }
 
-    blk1 = img_open(image_opts, filename1, fmt1, flags, writethrough, quiet);
+    blk1 = img_open(image_opts, filename1, fmt1, flags, writethrough, quiet,
+                    unsafe_read);
     if (!blk1) {
         ret = 2;
         goto out3;
     }
 
-    blk2 = img_open(image_opts, filename2, fmt2, flags, writethrough, quiet);
+    blk2 = img_open(image_opts, filename2, fmt2, flags, writethrough, quiet,
+                    unsafe_read);
     if (!blk2) {
         ret = 2;
         goto out2;
@@ -1911,6 +1936,7 @@ static int img_convert(int argc, char **argv)
     bool image_opts = false;
     bool wr_in_order = true;
     long num_coroutines = 8;
+    bool unsafe_read = false;
 
     fmt = NULL;
     out_fmt = "raw";
@@ -1924,9 +1950,10 @@ static int img_convert(int argc, char **argv)
             {"help", no_argument, 0, 'h'},
             {"object", required_argument, 0, OPTION_OBJECT},
             {"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
+            {"unsafe-read", no_argument, 0, 'U'},
             {0, 0, 0, 0}
         };
-        c = getopt_long(argc, argv, "hf:O:B:ce6o:s:l:S:pt:T:qnm:W",
+        c = getopt_long(argc, argv, "hf:O:B:ce6o:s:l:S:pt:T:qnm:WU",
                         long_options, NULL);
         if (c == -1) {
             break;
@@ -2030,6 +2057,9 @@ static int img_convert(int argc, char **argv)
         case 'W':
             wr_in_order = false;
             break;
+        case 'U':
+            unsafe_read = true;
+            break;
         case OPTION_OBJECT:
             opts = qemu_opts_parse_noisily(&qemu_object_opts,
                                            optarg, true);
@@ -2097,7 +2127,8 @@ static int img_convert(int argc, char **argv)
     total_sectors = 0;
     for (bs_i = 0; bs_i < bs_n; bs_i++) {
         blk[bs_i] = img_open(image_opts, argv[optind + bs_i],
-                             fmt, src_flags, src_writethrough, quiet);
+                             fmt, src_flags, src_writethrough, quiet,
+                             unsafe_read);
         if (!blk[bs_i]) {
             ret = -1;
             goto out;
@@ -2242,7 +2273,8 @@ static int img_convert(int argc, char **argv)
      * the bdrv_create() call which takes different params.
      * Not critical right now, so fix can wait...
      */
-    out_blk = img_open_file(out_filename, out_fmt, flags, writethrough, quiet);
+    out_blk = img_open_file(out_filename, out_fmt, flags, writethrough, quiet,
+                            unsafe_read);
     if (!out_blk) {
         ret = -1;
         goto out;
@@ -2413,7 +2445,7 @@ static gboolean str_equal_func(gconstpointer a, gconstpointer b)
 static ImageInfoList *collect_image_info_list(bool image_opts,
                                               const char *filename,
                                               const char *fmt,
-                                              bool chain)
+                                              bool chain, bool unsafe)
 {
     ImageInfoList *head = NULL;
     ImageInfoList **last = &head;
@@ -2436,7 +2468,8 @@ static ImageInfoList *collect_image_info_list(bool image_opts,
         g_hash_table_insert(filenames, (gpointer)filename, NULL);
 
         blk = img_open(image_opts, filename, fmt,
-                       BDRV_O_NO_BACKING | BDRV_O_NO_IO, false, false);
+                       BDRV_O_NO_BACKING | BDRV_O_NO_IO, false, false,
+                       unsafe);
         if (!blk) {
             goto err;
         }
@@ -2488,6 +2521,7 @@ static int img_info(int argc, char **argv)
     const char *filename, *fmt, *output;
     ImageInfoList *list;
     bool image_opts = false;
+    bool unsafe_read = false;
 
     fmt = NULL;
     output = NULL;
@@ -2500,9 +2534,10 @@ static int img_info(int argc, char **argv)
             {"backing-chain", no_argument, 0, OPTION_BACKING_CHAIN},
             {"object", required_argument, 0, OPTION_OBJECT},
             {"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
+            {"unsafe-read", no_argument, 0, 'U'},
             {0, 0, 0, 0}
         };
-        c = getopt_long(argc, argv, "f:h",
+        c = getopt_long(argc, argv, "f:hU",
                         long_options, &option_index);
         if (c == -1) {
             break;
@@ -2515,6 +2550,9 @@ static int img_info(int argc, char **argv)
         case 'f':
             fmt = optarg;
             break;
+        case 'U':
+            unsafe_read = true;
+            break;
         case OPTION_OUTPUT:
             output = optarg;
             break;
@@ -2554,7 +2592,8 @@ static int img_info(int argc, char **argv)
         return 1;
     }
 
-    list = collect_image_info_list(image_opts, filename, fmt, chain);
+    list = collect_image_info_list(image_opts, filename, fmt, chain,
+                                   unsafe_read);
     if (!list) {
         return 1;
     }
@@ -2700,6 +2739,7 @@ static int img_map(int argc, char **argv)
     MapEntry curr = { .length = 0 }, next;
     int ret = 0;
     bool image_opts = false;
+    bool unsafe_read = false;
 
     fmt = NULL;
     output = NULL;
@@ -2711,9 +2751,10 @@ static int img_map(int argc, char **argv)
             {"output", required_argument, 0, OPTION_OUTPUT},
             {"object", required_argument, 0, OPTION_OBJECT},
             {"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
+            {"unsafe-read", no_argument, 0, 'U'},
             {0, 0, 0, 0}
         };
-        c = getopt_long(argc, argv, "f:h",
+        c = getopt_long(argc, argv, "f:hU",
                         long_options, &option_index);
         if (c == -1) {
             break;
@@ -2726,6 +2767,9 @@ static int img_map(int argc, char **argv)
         case 'f':
             fmt = optarg;
             break;
+        case 'U':
+            unsafe_read = true;
+            break;
         case OPTION_OUTPUT:
             output = optarg;
             break;
@@ -2762,7 +2806,7 @@ static int img_map(int argc, char **argv)
         return 1;
     }
 
-    blk = img_open(image_opts, filename, fmt, 0, false, false);
+    blk = img_open(image_opts, filename, fmt, 0, false, false, unsafe_read);
     if (!blk) {
         return 1;
     }
@@ -2825,6 +2869,7 @@ static int img_snapshot(int argc, char **argv)
     bool quiet = false;
     Error *err = NULL;
     bool image_opts = false;
+    bool unsafe_read = false;
 
     bdrv_oflags = BDRV_O_RDWR;
     /* Parse commandline parameters */
@@ -2833,9 +2878,10 @@ static int img_snapshot(int argc, char **argv)
             {"help", no_argument, 0, 'h'},
             {"object", required_argument, 0, OPTION_OBJECT},
             {"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
+            {"unsafe-read", no_argument, 0, 'U'},
             {0, 0, 0, 0}
         };
-        c = getopt_long(argc, argv, "la:c:d:hq",
+        c = getopt_long(argc, argv, "la:c:d:hqU",
                         long_options, NULL);
         if (c == -1) {
             break;
@@ -2880,6 +2926,9 @@ static int img_snapshot(int argc, char **argv)
         case 'q':
             quiet = true;
             break;
+        case 'U':
+            unsafe_read = true;
+            break;
         case OPTION_OBJECT: {
             QemuOpts *opts;
             opts = qemu_opts_parse_noisily(&qemu_object_opts,
@@ -2906,7 +2955,8 @@ static int img_snapshot(int argc, char **argv)
     }
 
     /* Open the image */
-    blk = img_open(image_opts, filename, NULL, bdrv_oflags, false, quiet);
+    blk = img_open(image_opts, filename, NULL, bdrv_oflags, false, quiet,
+                   unsafe_read);
     if (!blk) {
         return 1;
     }
@@ -2970,6 +3020,7 @@ static int img_rebase(int argc, char **argv)
     int c, flags, src_flags, ret;
     bool writethrough, src_writethrough;
     int unsafe = 0;
+    int unsafe_read = 0;
     int progress = 0;
     bool quiet = false;
     Error *local_err = NULL;
@@ -2986,9 +3037,10 @@ static int img_rebase(int argc, char **argv)
             {"help", no_argument, 0, 'h'},
             {"object", required_argument, 0, OPTION_OBJECT},
             {"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
+            {"unsafe-read", no_argument, 0, 'U'},
             {0, 0, 0, 0}
         };
-        c = getopt_long(argc, argv, "hf:F:b:upt:T:q",
+        c = getopt_long(argc, argv, "hf:F:b:upt:T:qU",
                         long_options, NULL);
         if (c == -1) {
             break;
@@ -3033,6 +3085,9 @@ static int img_rebase(int argc, char **argv)
         case OPTION_IMAGE_OPTS:
             image_opts = true;
             break;
+        case 'U':
+            unsafe_read = 1;
+            break;
         }
     }
 
@@ -3081,7 +3136,8 @@ static int img_rebase(int argc, char **argv)
      * Ignore the old backing file for unsafe rebase in case we want to correct
      * the reference to a renamed or moved backing file.
      */
-    blk = img_open(image_opts, filename, fmt, flags, writethrough, quiet);
+    blk = img_open(image_opts, filename, fmt, flags, writethrough, quiet,
+                   unsafe_read);
     if (!blk) {
         ret = -1;
         goto out;
@@ -3106,6 +3162,9 @@ static int img_rebase(int argc, char **argv)
             qdict_put(options, "driver", qstring_from_str(bs->backing_format));
         }
 
+        if (unsafe_read) {
+            src_flags |= BDRV_O_UNSAFE_READ;
+        }
         bdrv_get_backing_filename(bs, backing_name, sizeof(backing_name));
         blk_old_backing = blk_new_open(backing_name, NULL,
                                        options, src_flags, &local_err);
@@ -3321,6 +3380,7 @@ static int img_resize(int argc, char **argv)
     bool quiet = false;
     BlockBackend *blk = NULL;
     QemuOpts *param;
+    bool unsafe_read = true;
 
     static QemuOptsList resize_options = {
         .name = "resize_options",
@@ -3353,9 +3413,10 @@ static int img_resize(int argc, char **argv)
             {"help", no_argument, 0, 'h'},
             {"object", required_argument, 0, OPTION_OBJECT},
             {"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
+            {"unsafe-read", no_argument, 0, 'U'},
             {0, 0, 0, 0}
         };
-        c = getopt_long(argc, argv, "f:hq",
+        c = getopt_long(argc, argv, "f:hqU",
                         long_options, NULL);
         if (c == -1) {
             break;
@@ -3371,6 +3432,9 @@ static int img_resize(int argc, char **argv)
         case 'q':
             quiet = true;
             break;
+        case 'U':
+            unsafe_read = true;
+            break;
         case OPTION_OBJECT: {
             QemuOpts *opts;
             opts = qemu_opts_parse_noisily(&qemu_object_opts,
@@ -3423,7 +3487,8 @@ static int img_resize(int argc, char **argv)
     qemu_opts_del(param);
 
     blk = img_open(image_opts, filename, fmt,
-                   BDRV_O_RDWR | BDRV_O_RESIZE, false, quiet);
+                   BDRV_O_RDWR | BDRV_O_RESIZE, false, quiet,
+                   unsafe_read);
     if (!blk) {
         ret = -1;
         goto out;
@@ -3484,6 +3549,7 @@ static int img_amend(int argc, char **argv)
     BlockBackend *blk = NULL;
     BlockDriverState *bs = NULL;
     bool image_opts = false;
+    bool unsafe_read = false;
 
     cache = BDRV_DEFAULT_CACHE;
     for (;;) {
@@ -3491,9 +3557,10 @@ static int img_amend(int argc, char **argv)
             {"help", no_argument, 0, 'h'},
             {"object", required_argument, 0, OPTION_OBJECT},
             {"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
+            {"unsafe-read", no_argument, 0, 'U'},
             {0, 0, 0, 0}
         };
-        c = getopt_long(argc, argv, "ho:f:t:pq",
+        c = getopt_long(argc, argv, "ho:f:t:pqU",
                         long_options, NULL);
         if (c == -1) {
             break;
@@ -3581,7 +3648,8 @@ static int img_amend(int argc, char **argv)
         goto out;
     }
 
-    blk = img_open(image_opts, filename, fmt, flags, writethrough, quiet);
+    blk = img_open(image_opts, filename, fmt, flags, writethrough, quiet,
+                   unsafe_read);
     if (!blk) {
         ret = -1;
         goto out;
@@ -3749,6 +3817,7 @@ static int img_bench(int argc, char **argv)
     bool writethrough = false;
     struct timeval t1, t2;
     int i;
+    bool unsafe_read = false;
 
     for (;;) {
         static const struct option long_options[] = {
@@ -3757,9 +3826,10 @@ static int img_bench(int argc, char **argv)
             {"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
             {"pattern", required_argument, 0, OPTION_PATTERN},
             {"no-drain", no_argument, 0, OPTION_NO_DRAIN},
+            {"unsafe-read", no_argument, 0, 'U'},
             {0, 0, 0, 0}
         };
-        c = getopt_long(argc, argv, "hc:d:f:no:qs:S:t:w", long_options, NULL);
+        c = getopt_long(argc, argv, "hc:d:f:no:qs:S:t:wU", long_options, NULL);
         if (c == -1) {
             break;
         }
@@ -3848,6 +3918,9 @@ static int img_bench(int argc, char **argv)
             flags |= BDRV_O_RDWR;
             is_write = true;
             break;
+        case 'U':
+            unsafe_read = true;
+            break;
         case OPTION_PATTERN:
         {
             unsigned long res;
@@ -3895,7 +3968,8 @@ static int img_bench(int argc, char **argv)
         goto out;
     }
 
-    blk = img_open(image_opts, filename, fmt, flags, writethrough, quiet);
+    blk = img_open(image_opts, filename, fmt, flags, writethrough, quiet,
+                   unsafe_read);
     if (!blk) {
         ret = -1;
         goto out;
@@ -4062,6 +4136,7 @@ static int img_dd(int argc, char **argv)
     const char *fmt = NULL;
     int64_t size = 0;
     int64_t block_count = 0, out_pos, in_pos;
+    bool unsafe_read = false;
     struct DdInfo dd = {
         .flags = 0,
         .count = 0,
@@ -4090,10 +4165,11 @@ static int img_dd(int argc, char **argv)
     const struct option long_options[] = {
         { "help", no_argument, 0, 'h'},
         { "image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
+        { "unsafe-read", no_argument, 0, 'U'},
         { 0, 0, 0, 0 }
     };
 
-    while ((c = getopt_long(argc, argv, "hf:O:", long_options, NULL))) {
+    while ((c = getopt_long(argc, argv, "hf:O:U", long_options, NULL))) {
         if (c == EOF) {
             break;
         }
@@ -4111,6 +4187,9 @@ static int img_dd(int argc, char **argv)
         case 'h':
             help();
             break;
+        case 'U':
+            unsafe_read = true;
+            break;
         case OPTION_IMAGE_OPTS:
             image_opts = true;
             break;
@@ -4155,7 +4234,8 @@ static int img_dd(int argc, char **argv)
         ret = -1;
         goto out;
     }
-    blk1 = img_open(image_opts, in.filename, fmt, 0, false, false);
+    blk1 = img_open(image_opts, in.filename, fmt, 0, false, false,
+                    unsafe_read);
 
     if (!blk1) {
         ret = -1;
@@ -4223,7 +4303,7 @@ static int img_dd(int argc, char **argv)
     }
 
     blk2 = img_open(image_opts, out.filename, out_fmt, BDRV_O_RDWR,
-                    false, false);
+                    false, false, unsafe_read);
 
     if (!blk2) {
         ret = -1;
-- 
2.9.3

[Qemu-devel] [PATCH RFC 3/3] qemu-io: Add --unsafe-read option

[Fam Zheng]

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 qemu-io.c | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/qemu-io.c b/qemu-io.c
index 427cbae..f3616ee 100644
--- a/qemu-io.c
+++ b/qemu-io.c
@@ -53,7 +53,8 @@ static const cmdinfo_t close_cmd = {
     .oneline    = "close the current open file",
 };
 
-static int openfile(char *name, int flags, bool writethrough, QDict *opts)
+static int openfile(char *name, int flags, bool writethrough, bool unsafe_read,
+                    QDict *opts)
 {
     Error *local_err = NULL;
     BlockDriverState *bs;
@@ -64,6 +65,9 @@ static int openfile(char *name, int flags, bool writethrough, QDict *opts)
         return 1;
     }
 
+    if (unsafe_read) {
+        flags |= BDRV_O_UNSAFE_READ;
+    }
     qemuio_blk = blk_new_open(name, NULL, opts, flags, &local_err);
     if (!qemuio_blk) {
         error_reportf_err(local_err, "can't open%s%s: ",
@@ -108,6 +112,7 @@ static void open_help(void)
 " -r, -- open file read-only\n"
 " -s, -- use snapshot file\n"
 " -n, -- disable host cache, short for -t none\n"
+" -U, -- accept unsafe opening of the image even if it's in use by another process\n"
 " -k, -- use kernel AIO implementation (on Linux only)\n"
 " -t, -- use the given cache mode for the image\n"
 " -d, -- use the given discard mode for the image\n"
@@ -124,7 +129,7 @@ static const cmdinfo_t open_cmd = {
     .argmin     = 1,
     .argmax     = -1,
     .flags      = CMD_NOFILE_OK,
-    .args       = "[-rsnk] [-t cache] [-d discard] [-o options] [path]",
+    .args       = "[-rsnkU] [-t cache] [-d discard] [-o options] [path]",
     .oneline    = "open the file specified by path",
     .help       = open_help,
 };
@@ -147,8 +152,9 @@ static int open_f(BlockBackend *blk, int argc, char **argv)
     int c;
     QemuOpts *qopts;
     QDict *opts;
+    bool unsafe_read = false;
 
-    while ((c = getopt(argc, argv, "snro:kt:d:")) != -1) {
+    while ((c = getopt(argc, argv, "snro:kt:d:U")) != -1) {
         switch (c) {
         case 's':
             flags |= BDRV_O_SNAPSHOT;
@@ -188,6 +194,9 @@ static int open_f(BlockBackend *blk, int argc, char **argv)
                 return 0;
             }
             break;
+        case 'U':
+            unsafe_read = true;
+            break;
         default:
             qemu_opts_reset(&empty_opts);
             return qemuio_command_usage(&open_cmd);
@@ -211,9 +220,9 @@ static int open_f(BlockBackend *blk, int argc, char **argv)
     qemu_opts_reset(&empty_opts);
 
     if (optind == argc - 1) {
-        return openfile(argv[optind], flags, writethrough, opts);
+        return openfile(argv[optind], flags, writethrough, unsafe_read, opts);
     } else if (optind == argc) {
-        return openfile(NULL, flags, writethrough, opts);
+        return openfile(NULL, flags, writethrough, unsafe_read, opts);
     } else {
         QDECREF(opts);
         return qemuio_command_usage(&open_cmd);
@@ -452,6 +461,7 @@ int main(int argc, char **argv)
         { "trace", required_argument, NULL, 'T' },
         { "object", required_argument, NULL, OPTION_OBJECT },
         { "image-opts", no_argument, NULL, OPTION_IMAGE_OPTS },
+        { "unsafe-read", no_argument, 0, 'U'},
         { NULL, 0, NULL, 0 }
     };
     int c;
@@ -462,6 +472,7 @@ int main(int argc, char **argv)
     QDict *opts = NULL;
     const char *format = NULL;
     char *trace_file = NULL;
+    bool unsafe_read = false;
 
 #ifdef CONFIG_POSIX
     signal(SIGPIPE, SIG_IGN);
@@ -524,6 +535,9 @@ int main(int argc, char **argv)
         case 'h':
             usage(progname);
             exit(0);
+        case 'U':
+            unsafe_read = true;
+            break;
         case OPTION_OBJECT: {
             QemuOpts *qopts;
             qopts = qemu_opts_parse_noisily(&qemu_object_opts,
@@ -595,7 +609,7 @@ int main(int argc, char **argv)
                 exit(1);
             }
             opts = qemu_opts_to_qdict(qopts, NULL);
-            if (openfile(NULL, flags, writethrough, opts)) {
+            if (openfile(NULL, flags, writethrough, unsafe_read, opts)) {
                 exit(1);
             }
         } else {
@@ -603,7 +617,7 @@ int main(int argc, char **argv)
                 opts = qdict_new();
                 qdict_put(opts, "driver", qstring_from_str(format));
             }
-            if (openfile(argv[optind], flags, writethrough, opts)) {
+            if (openfile(argv[optind], flags, writethrough, unsafe_read, opts)) {
                 exit(1);
             }
         }
-- 
2.9.3

Re: [Qemu-devel] [Qemu-block] [PATCH RFC 0/3] block: Backdoor to skip image locking in qemu-io/qemu-img

[John Snow]

On 03/13/2017 10:39 PM, Fam Zheng wrote:
> Hi Kevin,
> 
> This tries to capture your idea to add a explicit command option in qemu-io and
> qemu-img for user to specify "expect inconsistent data when reading image".
> It's stored as a BDRV_O_ flag internally, I don't know if there is a cleaner
> way or not.
> 
> It's depended on by image locking series because several test cases need to be
> updated to use this flag.
> 
> Fam
> 
> Fam Zheng (3):
>   block: Introduce BDRV_O_UNSAFE_READ
>   qemu-img: Add --unsafe-read option to subcommands
>   qemu-io: Add --unsafe-read option
> 
>  block/block-backend.c |   2 +-
>  include/block/block.h |   1 +
>  qemu-img.c            | 148 ++++++++++++++++++++++++++++++++++++++------------
>  qemu-io.c             |  28 +++++++---
>  4 files changed, 137 insertions(+), 42 deletions(-)
> 

Month old with no replies or ping, DOA?

--js

Re: [Qemu-devel] [Qemu-block] [PATCH RFC 0/3] block: Backdoor to skip image locking in qemu-io/qemu-img

[Fam Zheng]

On Thu, 04/13 21:14, John Snow wrote:
> 
> 
> On 03/13/2017 10:39 PM, Fam Zheng wrote:
> > Hi Kevin,
> > 
> > This tries to capture your idea to add a explicit command option in qemu-io and
> > qemu-img for user to specify "expect inconsistent data when reading image".
> > It's stored as a BDRV_O_ flag internally, I don't know if there is a cleaner
> > way or not.
> > 
> > It's depended on by image locking series because several test cases need to be
> > updated to use this flag.
> > 
> > Fam
> > 
> > Fam Zheng (3):
> >   block: Introduce BDRV_O_UNSAFE_READ
> >   qemu-img: Add --unsafe-read option to subcommands
> >   qemu-io: Add --unsafe-read option
> > 
> >  block/block-backend.c |   2 +-
> >  include/block/block.h |   1 +
> >  qemu-img.c            | 148 ++++++++++++++++++++++++++++++++++++++------------
> >  qemu-io.c             |  28 +++++++---
> >  4 files changed, 137 insertions(+), 42 deletions(-)
> > 
> 
> Month old with no replies or ping, DOA?

Yes, ping? :)

I reckon RFC patches were less prioritized in the happy busy freeze. But if no
objection shows up, this series will be integrated in the next version of imgae
locking series.

Fam

Re: [Qemu-devel] [PATCH RFC 1/3] block: Introduce BDRV_O_UNSAFE_READ

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 1263 bytes --]

On 03/13/2017 09:39 PM, Fam Zheng wrote:
> This flag clears out the "consistent read" permission that blk_new_open
> requests.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  block/block-backend.c | 2 +-
>  include/block/block.h | 1 +
>  2 files changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/block/block-backend.c b/block/block-backend.c
> index 5742c09..99428ee 100644
> --- a/block/block-backend.c
> +++ b/block/block-backend.c
> @@ -197,7 +197,7 @@ BlockBackend *blk_new_open(const char *filename, const char *reference,
>       * caller of blk_new_open() doesn't make use of the permissions, but they
>       * shouldn't hurt either. We can still share everything here because the
>       * guest devices will add their own blockers if they can't share. */
> -    perm = BLK_PERM_CONSISTENT_READ;
> +    perm = flags & BDRV_O_UNSAFE_READ ? 0 : BLK_PERM_CONSISTENT_READ;

A bit awkward that we have to add an option that requests negation of a
permission under the hood, but looks like it is the least-invasive way
to get what we want.

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 604 bytes --]

Re: [Qemu-devel] [PATCH RFC 2/3] qemu-img: Add --unsafe-read option to subcommands

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 1732 bytes --]

On 03/13/2017 09:39 PM, Fam Zheng wrote:
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  qemu-img.c | 148 +++++++++++++++++++++++++++++++++++++++++++++++--------------
>  1 file changed, 114 insertions(+), 34 deletions(-)
> 

> @@ -2711,9 +2751,10 @@ static int img_map(int argc, char **argv)
>              {"output", required_argument, 0, OPTION_OUTPUT},
>              {"object", required_argument, 0, OPTION_OBJECT},
>              {"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
> +            {"unsafe-read", no_argument, 0, 'U'},
>              {0, 0, 0, 0}
>          };
> -        c = getopt_long(argc, argv, "f:h",
> +        c = getopt_long(argc, argv, "f:hU",

Yay for 'U' being an unambiguous mnemonic that we could use on all the
commands.  You got lucky (it gets ever harder to add new options, as our
letters get thinner ;)

> @@ -2970,6 +3020,7 @@ static int img_rebase(int argc, char **argv)
>      int c, flags, src_flags, ret;
>      bool writethrough, src_writethrough;
>      int unsafe = 0;
> +    int unsafe_read = 0;

bool, please.  (Just because existing code is lousy with using an int
for a bool doesn't mean we should perpetuate it)


> @@ -3033,6 +3085,9 @@ static int img_rebase(int argc, char **argv)
>          case OPTION_IMAGE_OPTS:
>              image_opts = true;
>              break;
> +        case 'U':
> +            unsafe_read = 1;

s/1/true/

Good patch, but missing documentation updates to --help/man page.  So,
as encouragement to add that when you drop the RFC, I'll withhold my R-b
until then. ;)

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 604 bytes --]

Re: [Qemu-devel] [PATCH RFC 3/3] qemu-io: Add --unsafe-read option

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 955 bytes --]

On 03/13/2017 09:39 PM, Fam Zheng wrote:
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  qemu-io.c | 28 +++++++++++++++++++++-------
>  1 file changed, 21 insertions(+), 7 deletions(-)
> 
> @@ -108,6 +112,7 @@ static void open_help(void)
>  " -r, -- open file read-only\n"
>  " -s, -- use snapshot file\n"
>  " -n, -- disable host cache, short for -t none\n"
> +" -U, -- accept unsafe opening of the image even if it's in use by another process\n"

Long line (exceeds 80 columns of output); can we shorten it?  Maybe

 -U, allow unsafe reads when another process is writing

You did get 'qemu-io -c "help open"' adjusted, but I don't see where you
adjusted 'qemu-io --help'.  Since both places gained a -U, you still
need more documentation. But at least there is no man page to worry
about here.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 604 bytes --]

Re: [Qemu-devel] [PATCH RFC 2/3] qemu-img: Add --unsafe-read option to subcommands

[Fam Zheng]

On Tue, 04/18 08:20, Eric Blake wrote:
> bool, please.  (Just because existing code is lousy with using an int
> for a bool doesn't mean we should perpetuate it)

OK, will fix.

> 
> 
> > @@ -3033,6 +3085,9 @@ static int img_rebase(int argc, char **argv)
> >          case OPTION_IMAGE_OPTS:
> >              image_opts = true;
> >              break;
> > +        case 'U':
> > +            unsafe_read = 1;
> 
> s/1/true/
> 
> Good patch, but missing documentation updates to --help/man page.  So,
> as encouragement to add that when you drop the RFC, I'll withhold my R-b
> until then. ;)

Yes, I'll add another patch for ease of review.

Fam

Re: [Qemu-devel] [PATCH RFC 3/3] qemu-io: Add --unsafe-read option

[Fam Zheng]

On Tue, 04/18 08:27, Eric Blake wrote:
> On 03/13/2017 09:39 PM, Fam Zheng wrote:
> > Signed-off-by: Fam Zheng <famz@redhat.com>
> > ---
> >  qemu-io.c | 28 +++++++++++++++++++++-------
> >  1 file changed, 21 insertions(+), 7 deletions(-)
> > 
> > @@ -108,6 +112,7 @@ static void open_help(void)
> >  " -r, -- open file read-only\n"
> >  " -s, -- use snapshot file\n"
> >  " -n, -- disable host cache, short for -t none\n"
> > +" -U, -- accept unsafe opening of the image even if it's in use by another process\n"
> 
> Long line (exceeds 80 columns of output); can we shorten it?  Maybe
> 
>  -U, allow unsafe reads when another process is writing
> 
> You did get 'qemu-io -c "help open"' adjusted, but I don't see where you
> adjusted 'qemu-io --help'.  Since both places gained a -U, you still
> need more documentation. But at least there is no man page to worry
> about here.

Sounds good. will fix both issues.

Many thanks for the review!

Fam