The state of Giant lock in the file systems?

[Ivan Voras]

On 8 November 2010 16:04, John Baldwin <jhb at freebsd.org> wrote:
> On Monday, November 08, 2010 7:28:26 am Ivan Voras wrote:
>> I was looking at fusefs sources and there is a dance it does with the
>> Giant lock which looks fishy.
>>
>> Grepping for "-ir giant" in /sys/fs on 8-stable shows only a handful of
>> mentionings, but if I understand it correctly only these "active" instances:
>>
>> 1) one set of mtx_assert() calls on it in pseudofs, which I can't figure
>> out what they're guarding
>> 2) some manual locking and unlocking in nfsclient which appears to only
>> guard printf() (???)
>> 3) some more locking in nfsserver which apparently is only there to
>> guard the underlying local file system
>> 4) coda, which appears to be the only one marked with D_NEEDGIANT, but
>> doesn't do much of its own interfacing with it
>>
>> Except for these, is there any more magic that would need to be resolved
>> to excise Giant from VFS?
>>
>> Would it be correct to think that coda is the single biggest obstacle?
>
> Err, all the VFS_LOCK_GIANT() stuff for filesystems that do not have
> MNTK_MPSAFE set.  I believe the currently MPSAFE fs's are UFS, ZFS, MSDOSFS,
> CD9660, UDF, NFS client, and devfs.  I think all others are !MPSAFE still.

Thanks!

It seemed too easy to be true.