Re: unlink(nonexistent): EROFS or ENOENT?
From: Michael Tokarev
Date: Mon Jun 06 2011 - 13:18:54 EST
06.06.2011 21:13, Michael Tokarev wrote:
> Thank you for the answer. I thought noone will reply... ;)
> 06.06.2011 07:39, Ted Ts'o wrote:
>> On Sun, May 29, 2011 at 08:08:55PM +0400, Michael Tokarev wrote:
>>> Just noticed that at least on ext4, unlinking a
>>> non-existing file from a read-only filesystem
>>> results in EROFS instead of ENOENT. I'd expect
>>> it return ENOENT - it is more logical, at least
>>> in my opinion.
>>> For one, (readonly) NFS mount returns ENOENT in
>>> this case.
>> Um, it doesn't for me. Testing on v3.0-rc1:
>> # ls /test/foo; rm /test/foo
>> ls: cannot access /test/foo: No such file or directory
>> rm: cannot remove `/test/foo': No such file or directory
> This is a hack in coreutils rm to work around this
> kernel change. The comment at
> /* The unlinkat from kernels like linux-2.6.32 reports EROFS even for
> nonexistent files. When the file is indeed missing, map that to ENOENT,
> so that rm -f ignores it, as required. Even without -f, this is useful
> because it makes rm print the more precise diagnostic. */
> so that rm(1) calls stat(2) to see if the file actually
> exist if unlinkat() returned EROFS, and turns this errno
> into ENOENT.
And another followup to this, -- the original case when I actually
noticed the problem. A readonly-mounted root filesystem with /etc
in git (the repository is in /var, symlinked from /etc/.git). I
deleted a few files from /etc (when it was readwrite), and noticed
that I forgot to commit the change. So I used `git rm oldfiles' and
voila, git, for the first time, refused to commit stuff for me in
this configuration, -- before, I was always able to _commit_ the
changes even if the working tree is read-only. It works for
everything but not for unlinks.
> That is, rm(1) output is not a good indicator. Use
> strace rm -f /test/foo 2>&1 | grep unlink
> to see the actual errno reported by the kernel.
> Here's the POSIX description of unlink (and unlinkat) again:
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