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Subjecttruncate() error values (was Re: Floppy disk strange behavior)


On Wed, 10 Jan 2001 Andries.Brouwer@cwi.nl wrote:

> >> dd: advancing past 1 blocks in output file `/dev/fd0': Permission denied
>
> > dd bug. It tries to ftruncate() the output file and gets all upset when
> > kernel refuses to truncate a block device (surprise, surprise).
>
> Yes. But EPERM means that something is wrong with privileges.
EACCES, actually.
> One would expect EINVAL or so when something is wrong with the
> way the routine was called.

Oh, agreed. Patch I've sent to Linus and posted on l-k more than a month ago:

diff -urN rc12-pre5/fs/open.c rc12-pre5-truncate/fs/open.c
--- rc12-pre5/fs/open.c Wed Nov 29 21:37:31 2000
+++ rc12-pre5-truncate/fs/open.c Tue Dec 5 14:53:59 2000
@@ -102,7 +102,12 @@
goto out;
inode = nd.dentry->d_inode;

- error = -EACCES;
+ /* For directories it's -EISDIR, for other non-regulars - -EINVAL */
+ error = -EISDIR;
+ if (S_ISDIR(inode->i_mode))
+ goto dput_and_out;
+
+ error = -EINVAL;
if (!S_ISREG(inode->i_mode))
goto dput_and_out;

@@ -163,7 +168,7 @@
goto out;
dentry = file->f_dentry;
inode = dentry->d_inode;
- error = -EACCES;
+ error = -EINVAL;
if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
goto out_putf;
error = -EPERM;
That's test12-pre5. And yes, the case of files opened with O_RDONLY should
be -EINVAL according to
* our own manpages
* POSIX
* *BSD behaviour
* Solaris behaviour
* manpages of all Unices I've seen.
-EACCES is wrong here. More logical, but...

Linus, I realize that we have a moratorium on patches. It's certainly not
a critical one, but it probably ought to be applied at some point. Could
you tell what time would be OK for resubmitting it? All it changes is
* error returned for truncate() on directories (EACCES -> EISDIR)
* error returned for truncate() on other non-file (EACCES -> EINVAL)
* error returned for ftruncate() on O_RDONLY fds (EACCES -> EINVAL)
* error returned for ftruncate() on non-files (EACCES -> EINVAL)
In all cases new error values are what we are required to do by POSIX, SuS,
our own manpages, manpages of other Unices and actual behaviour of other
Unices.

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