[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

[Libguestfs] [PATCH libnbd 1/2] nbdcopy: Do not use trim for zeroing



Current code uses NBD_CMD_TRIM for writing zeroes without allocating
space (--allocate not specified). This incorrect and can lead to
corrupting the target image.

NBD manual warns about NBD_CMD_TRIM:

    After issuing this command, a client MUST NOT make any assumptions
    about the contents of the export affected by this command, until
    overwriting it again with NBD_CMD_WRITE or NBD_CMD_WRITE_ZEROES

Add allocate flag to the zero operation, to allow zeroing by punching
hole (default) or zeroing by allocating space.

nbd-ops use NBD_CMD_WRITE_ZEROES with or without NBD_FLAG_NO_HOLE
flag. file-ops use fallocate with PUNCH_HOLE or ZERO_RANGE flag.

The copy-sparse tests was modified to require zero operation with
may_trim flag.

Signed-off-by: Nir Soffer <nsoffer redhat com>
---
 copy/copy-sparse.sh         | 66 ++++++++++++++++++-------------------
 copy/file-ops.c             | 49 +++++++++++++++++++--------
 copy/multi-thread-copying.c | 20 ++++-------
 copy/nbd-ops.c              |  8 ++---
 copy/nbdcopy.h              |  5 +--
 copy/null-ops.c             |  4 +--
 copy/synch-copying.c        |  8 ++---
 7 files changed, 88 insertions(+), 72 deletions(-)

diff --git a/copy/copy-sparse.sh b/copy/copy-sparse.sh
index 846767b..c43b41a 100755
--- a/copy/copy-sparse.sh
+++ b/copy/copy-sparse.sh
@@ -33,7 +33,7 @@ cleanup_fn rm -f $out
 
 # Copy from a sparse data disk to an nbdkit-eval-plugin instance which
 # is logging everything.  This allows us to see exactly what nbdcopy
-# is writing, to ensure it is writing and trimming the target as
+# is writing, to ensure it is writing and zeroing the target as
 # expected.
 $VG nbdcopy -S 0 -- \
     [ nbdkit --exit-with-parent data data='
@@ -60,38 +60,38 @@ if [ "$(cat $out)" != "pwrite 1 4294967296
 pwrite 32768 0
 pwrite 32768 1073709056
 pwrite 32768 4294934528
-trim 134184960 32768
-trim 134184960 4160749568
-trim 134184960 939524096
-trim 134217728 1073741824
-trim 134217728 1207959552
-trim 134217728 134217728
-trim 134217728 1342177280
-trim 134217728 1476395008
-trim 134217728 1610612736
-trim 134217728 1744830464
-trim 134217728 1879048192
-trim 134217728 2013265920
-trim 134217728 2147483648
-trim 134217728 2281701376
-trim 134217728 2415919104
-trim 134217728 2550136832
-trim 134217728 268435456
-trim 134217728 2684354560
-trim 134217728 2818572288
-trim 134217728 2952790016
-trim 134217728 3087007744
-trim 134217728 3221225472
-trim 134217728 3355443200
-trim 134217728 3489660928
-trim 134217728 3623878656
-trim 134217728 3758096384
-trim 134217728 3892314112
-trim 134217728 402653184
-trim 134217728 4026531840
-trim 134217728 536870912
-trim 134217728 671088640
-trim 134217728 805306368" ]; then
+zero 134184960 32768 may_trim
+zero 134184960 4160749568 may_trim
+zero 134184960 939524096 may_trim
+zero 134217728 1073741824 may_trim
+zero 134217728 1207959552 may_trim
+zero 134217728 1342177280 may_trim
+zero 134217728 134217728 may_trim
+zero 134217728 1476395008 may_trim
+zero 134217728 1610612736 may_trim
+zero 134217728 1744830464 may_trim
+zero 134217728 1879048192 may_trim
+zero 134217728 2013265920 may_trim
+zero 134217728 2147483648 may_trim
+zero 134217728 2281701376 may_trim
+zero 134217728 2415919104 may_trim
+zero 134217728 2550136832 may_trim
+zero 134217728 2684354560 may_trim
+zero 134217728 268435456 may_trim
+zero 134217728 2818572288 may_trim
+zero 134217728 2952790016 may_trim
+zero 134217728 3087007744 may_trim
+zero 134217728 3221225472 may_trim
+zero 134217728 3355443200 may_trim
+zero 134217728 3489660928 may_trim
+zero 134217728 3623878656 may_trim
+zero 134217728 3758096384 may_trim
+zero 134217728 3892314112 may_trim
+zero 134217728 4026531840 may_trim
+zero 134217728 402653184 may_trim
+zero 134217728 536870912 may_trim
+zero 134217728 671088640 may_trim
+zero 134217728 805306368 may_trim" ]; then
     echo "$0: output does not match expected"
     exit 1
 fi
diff --git a/copy/file-ops.c b/copy/file-ops.c
index 2a239d0..d0b9447 100644
--- a/copy/file-ops.c
+++ b/copy/file-ops.c
@@ -100,10 +100,9 @@ file_synch_write (struct rw *rw,
 }
 
 static bool
-file_synch_trim (struct rw *rw, uint64_t offset, uint64_t count)
+file_punch_hole(int fd, uint64_t offset, uint64_t count)
 {
 #ifdef FALLOC_FL_PUNCH_HOLE
-  int fd = rw->u.local.fd;
   int r;
 
   r = fallocate (fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
@@ -113,17 +112,14 @@ file_synch_trim (struct rw *rw, uint64_t offset, uint64_t count)
     exit (EXIT_FAILURE);
   }
   return true;
-#else /* !FALLOC_FL_PUNCH_HOLE */
-  return false;
 #endif
+  return false;
 }
 
 static bool
-file_synch_zero (struct rw *rw, uint64_t offset, uint64_t count)
+file_zero_range(int fd, uint64_t offset, uint64_t count)
 {
-  if (S_ISREG (rw->u.local.stat.st_mode)) {
 #ifdef FALLOC_FL_ZERO_RANGE
-    int fd = rw->u.local.fd;
     int r;
 
     r = fallocate (fd, FALLOC_FL_ZERO_RANGE, offset, count);
@@ -133,11 +129,13 @@ file_synch_zero (struct rw *rw, uint64_t offset, uint64_t count)
     }
     return true;
 #endif
-  }
-  else if (S_ISBLK (rw->u.local.stat.st_mode) &&
-           IS_ALIGNED (offset | count, rw->u.local.sector_size)) {
+  return false;
+}
+
+static bool
+file_zeroout(int fd, uint64_t offset, uint64_t count)
+{
 #ifdef BLKZEROOUT
-    int fd = rw->u.local.fd;
     int r;
     uint64_t range[2] = {offset, count};
 
@@ -148,6 +146,31 @@ file_synch_zero (struct rw *rw, uint64_t offset, uint64_t count)
     }
     return true;
 #endif
+    return false;
+}
+
+static bool
+file_synch_trim (struct rw *rw, uint64_t offset, uint64_t count)
+{
+  return file_punch_hole(rw->u.local.fd, offset, count);
+}
+
+static bool
+file_synch_zero (struct rw *rw, uint64_t offset, uint64_t count, bool allocate)
+{
+  int fd = rw->u.local.fd;
+
+  if (S_ISREG (rw->u.local.stat.st_mode)) {
+    if (allocate) {
+        return file_zero_range (fd, offset, count);
+    } else {
+        return file_punch_hole (fd, offset, count);
+    }
+  }
+  else if (S_ISBLK (rw->u.local.stat.st_mode) &&
+           IS_ALIGNED (offset | count, rw->u.local.sector_size)) {
+    /* Always allocate, discard and gurantee zeroing. */
+    return file_zeroout (fd, offset, count);
   }
 
   return false;
@@ -197,9 +220,9 @@ file_asynch_trim (struct rw *rw, struct command *command,
 
 static bool
 file_asynch_zero (struct rw *rw, struct command *command,
-                  nbd_completion_callback cb)
+                  nbd_completion_callback cb, bool allocate)
 {
-  if (!file_synch_zero (rw, command->offset, command->slice.len))
+  if (!file_synch_zero (rw, command->offset, command->slice.len, allocate))
     return false;
   errno = 0;
   if (cb.callback (cb.user_data, &errno) == -1) {
diff --git a/copy/multi-thread-copying.c b/copy/multi-thread-copying.c
index 98b4056..8061787 100644
--- a/copy/multi-thread-copying.c
+++ b/copy/multi-thread-copying.c
@@ -485,11 +485,12 @@ finished_read (void *vp, int *error)
  * --destination-is-zero:
  *                 do nothing
  *
- * --allocated:    we must write zeroes either using an efficient
+ * --allocated:    write zeroes allocating space using an efficient
  *                 zeroing command or writing a command of zeroes
  *
- * (neither flag)  try trimming if supported, else write zeroes
- *                 as above
+ * (neither flag)  write zeroes punching a hole using an efficient
+ *                 zeroing command or fallback to writing a command
+ *                 of zeroes.
  *
  * This takes over ownership of the command and frees it eventually.
  */
@@ -501,22 +502,13 @@ fill_dst_range_with_zeroes (struct command *command)
   if (destination_is_zero)
     goto free_and_return;
 
-  if (!allocated) {
-    /* Try trimming. */
-    if (dst.ops->asynch_trim (&dst, command,
-                              (nbd_completion_callback) {
-                                .callback = free_command,
-                                .user_data = command,
-                              }))
-      return;
-  }
-
   /* Try efficient zeroing. */
   if (dst.ops->asynch_zero (&dst, command,
                             (nbd_completion_callback) {
                               .callback = free_command,
                               .user_data = command,
-                            }))
+                            },
+                            allocated))
     return;
 
   /* Fall back to loop writing zeroes.  This is going to be slow
diff --git a/copy/nbd-ops.c b/copy/nbd-ops.c
index 0bcf29b..f3a9744 100644
--- a/copy/nbd-ops.c
+++ b/copy/nbd-ops.c
@@ -97,13 +97,13 @@ nbd_ops_synch_trim (struct rw *rw, uint64_t offset, uint64_t count)
 }
 
 static bool
-nbd_ops_synch_zero (struct rw *rw, uint64_t offset, uint64_t count)
+nbd_ops_synch_zero (struct rw *rw, uint64_t offset, uint64_t count, bool allocate)
 {
   if (!rw->u.nbd.can_zero)
     return false;
 
   if (nbd_zero (rw->u.nbd.handles.ptr[0],
-                count, offset, LIBNBD_CMD_FLAG_NO_HOLE) == -1) {
+                count, offset, allocate ? LIBNBD_CMD_FLAG_NO_HOLE : 0) == -1) {
     fprintf (stderr, "%s: %s\n", rw->name, nbd_get_error ());
     exit (EXIT_FAILURE);
   }
@@ -158,7 +158,7 @@ nbd_ops_asynch_trim (struct rw *rw, struct command *command,
 
 static bool
 nbd_ops_asynch_zero (struct rw *rw, struct command *command,
-                     nbd_completion_callback cb)
+                     nbd_completion_callback cb, bool allocate)
 {
   if (!rw->u.nbd.can_zero)
     return false;
@@ -167,7 +167,7 @@ nbd_ops_asynch_zero (struct rw *rw, struct command *command,
 
   if (nbd_aio_zero (rw->u.nbd.handles.ptr[command->index],
                     command->slice.len, command->offset,
-                    cb, LIBNBD_CMD_FLAG_NO_HOLE) == -1) {
+                    cb, allocate ? LIBNBD_CMD_FLAG_NO_HOLE : 0) == -1) {
     fprintf (stderr, "%s: %s\n", rw->name, nbd_get_error ());
     exit (EXIT_FAILURE);
   }
diff --git a/copy/nbdcopy.h b/copy/nbdcopy.h
index 69fac2a..21d09bf 100644
--- a/copy/nbdcopy.h
+++ b/copy/nbdcopy.h
@@ -134,7 +134,8 @@ struct rw_ops {
   bool (*synch_trim) (struct rw *rw, uint64_t offset, uint64_t count);
 
   /* Synchronously zero.  If not possible, returns false. */
-  bool (*synch_zero) (struct rw *rw, uint64_t offset, uint64_t count);
+  bool (*synch_zero) (struct rw *rw, uint64_t offset, uint64_t count,
+                      bool allocate);
 
   /* Asynchronous I/O operations.  These start the operation and call
    * 'cb' on completion.
@@ -162,7 +163,7 @@ struct rw_ops {
    * returns false.
    */
   bool (*asynch_zero) (struct rw *rw, struct command *command,
-                       nbd_completion_callback cb);
+                       nbd_completion_callback cb, bool allocate);
 
   /* Number of asynchronous commands in flight for a particular thread. */
   unsigned (*in_flight) (struct rw *rw, uintptr_t index);
diff --git a/copy/null-ops.c b/copy/null-ops.c
index b2ca66f..0a7b0fb 100644
--- a/copy/null-ops.c
+++ b/copy/null-ops.c
@@ -63,7 +63,7 @@ null_synch_trim (struct rw *rw, uint64_t offset, uint64_t count)
 }
 
 static bool
-null_synch_zero (struct rw *rw, uint64_t offset, uint64_t count)
+null_synch_zero (struct rw *rw, uint64_t offset, uint64_t count, bool allocate)
 {
   return true;
 }
@@ -102,7 +102,7 @@ null_asynch_trim (struct rw *rw, struct command *command,
 
 static bool
 null_asynch_zero (struct rw *rw, struct command *command,
-                  nbd_completion_callback cb)
+                  nbd_completion_callback cb, bool allocate)
 {
   errno = 0;
   if (cb.callback (cb.user_data, &errno) == -1) {
diff --git a/copy/synch-copying.c b/copy/synch-copying.c
index 2712c10..37d2d7f 100644
--- a/copy/synch-copying.c
+++ b/copy/synch-copying.c
@@ -69,10 +69,10 @@ synch_copying (void)
         assert (exts.ptr[i].length <= count);
 
         if (exts.ptr[i].zero) {
-          if (!dst.ops->synch_trim (&dst, offset, exts.ptr[i].length) &&
-              !dst.ops->synch_zero (&dst, offset, exts.ptr[i].length)) {
-            /* If neither trimming nor efficient zeroing are possible,
-             * write zeroes the hard way.
+          if (!dst.ops->synch_zero (&dst, offset, exts.ptr[i].length, false) &&
+              !dst.ops->synch_zero (&dst, offset, exts.ptr[i].length, true)) {
+            /* If efficient zeroing (punching a hole or allocating space) are
+             * possible, write zeroes the hard way.
              */
             memset (buf, 0, exts.ptr[i].length);
             dst.ops->synch_write (&dst, buf, exts.ptr[i].length, offset);
-- 
2.26.2


[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]