xfs_io: actually issue 0 size writes

While testing some stuff in generic_write_checks() in the kernel I realized that you can't actually use xfs_io to send a 0-byte write in. This is actually a condition worth testing:

If count is zero and fd refers to a regular file, then write() may return a failure status if one of the errors below is detected. If no errors are detected, 0 will be returned without causing any other effect.

So fix that up.

Signed-off-by Eric Sandeen <[email protected]>

---

iff --git a/io/pwrite.c b/io/pwrite.c
index 54c3f78..26a7850 100644

io/pwrite.c +3 -1

@@ -163,7 +163,7 @@ write_buffer(
 	int		ops = 0;
 
 	*total = 0;
-	while (count > 0) {
+	while (count >= 0) {
 		if (fd > 0) {	/* input file given, read buffer first */
 			if (read_buffer(fd, skip + *total, bs, &bar, 0, 1) < 0)
 				break;

@@ -182,6 +182,8 @@ write_buffer(
 			break;
 		offset += bytes;
 		count -= bytes;
+		if (count == 0)
+			break;
 	}
 	return ops;
 }

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Quoted 9 lines · Eric Sandeen

While testing some stuff in generic_write_checks() in the kernel I realized that you can't actually use xfs_io to send a 0-byte write in. This is actually a condition worth testing:

If count is zero and fd refers to a regular file, then write() may return a failure status if one of the errors below is detected. If no errors are detected, 0 will be returned without causing any other effect.

As I understand the desire to be able to issue 0 size writes from xfs_io is to test the possibility of writing to a given fd. What kind of errors would you expect to test for?

Otherwise looks good.

Felix

While testing some stuff in generic_write_checks() in the kernel I realized that you can't actually use xfs_io to send a 0-byte write in. This is actually a condition worth testing:

If count is zero and fd refers to a regular file, then write() may return a failure status if one of the errors below is detected. If no errors are detected, 0 will be returned without causing any other effect.

So fix that up.

Signed-off-by Eric Sandeen <[email protected]>

Quoted 10 lines · Eric Sandeen

While testing some stuff in generic_write_checks() in the kernel I realized that you can't actually use xfs_io to send a 0-byte write in. This is actually a condition worth testing:

If count is zero and fd refers to a regular file, then write() may return a failure status if one of the errors below is detected. If no errors are detected, 0 will be returned without causing any other effect.

Quoted 3 lines

So fix that up.

Signed-off-by Eric Sandeen <[email protected]>

Any reason you didn't put this in despite two positive reviews?