On Tue, 28 Dec 2004, ramana wrote:
> Dear developers,
>
> Here is the bug in autofs3 module which causing so much pain. It simply
> stopped me from adding much more interesting features to Autodir
> http://www.intraperson.com/autodir/
Thanks for this.
You've provided some symptoms but you haven't provided any explanation as
to why this is a bug.
Can you explain why you need the kernel to honour a lookup for an already
deleted dentry?
This could be due to the way that autofs does a d_drop instead of a
d_delete in the directory unlink callback. However, the dentry, for all
intentional purposes, has already been deleted.
>
> Taken from Linux kernel 2.4 autofs module source.
>
> file: root.c
> function: autofs_root_lookup.
> protocol: 3
>
> /*
> * If this dentry is unhashed, then we shouldn't honour this
> * lookup even if the dentry is positive. Returning ENOENT here
> * doesn't do the right thing for all system calls, but it should
> * be OK for the operations we permit from an autofs.
> */
>
>
>
> /*
> if ( dentry->d_inode && d_unhashed(dentry) )
> return ERR_PTR(-ENOENT);
> */
>
>
>
> if ( dentry->d_inode && d_unhashed(dentry) ) {
> printk( "ENOENT for %s\n", dentry->d_name.name );
> return ERR_PTR(-ENOENT);
> }
>
> I added printk to easily trace it. To my surprise autofs 4 also has
> similar code.
>
> Because of this, user space test program reporting like this:
>
> fail : /test/t944 : No such file or directory
> fail : /test/t4187 : No such file or directory
> fail : /test/t100 : No such file or directory
> fail : /test/t806 : No such file or directory
> fail : /test/t3451 : No such file or directory
> fail : /test/t1790 : No such file or directory
> fail : /test/t3555 : No such file or directory
> fail : /test/t3098 : No such file or directory
> fail : /test/t4085 : No such file or directory
> fail : /test/t3935 : No such file or directory
>
> with corresponding kernel messages are,
>
> ENOENT for t944
> ENOENT for t4187
> ENOENT for t100
> ENOENT for t806
> ENOENT for t3451
> ENOENT for t1790
> ENOENT for t3555
> ENOENT for t3098
> ENOENT for t4085
> ENOENT for t3935
>
> The error rate as taken from months of stress tests -- ie ENOENT; is
> around 0.002% and increases as system load increases. Even at this rate
> I do not think it is acceptable in production systems.
>
> Thanks in advance.
>
> Regards
> ramana
>
> --
> http://www.intraperson.com
>
>
> _______________________________________________
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>
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