Re: [Patch] tmpfs: add fallocate support

[Dave Hansen <dave@linux.vnet.ibm.com>]

On Wed, 2011-11-16 at 15:21 +0800, Cong Wang wrote:
> ao? 2011a1'11ae??16ae?JPY 01:43, Dave Hansen a??e??:
> > On Tue, 2011-11-15 at 18:23 +0800, Cong Wang wrote:
> >>> +	if (!(mode&   FALLOC_FL_KEEP_SIZE)) {
> >>> +		ret = inode_newsize_ok(inode, (offset + len));
> >>> +		if (ret)
> >>> +			return ret;
> >>> +	}
> >
> > inode_newsize_ok()'s comments say:
> >
> >   * inode_newsize_ok must be called with i_mutex held.
> >
> > But I don't see any trace of it.
> 
> Hmm, even for tmpfs? I see none of the tmpfs code takes
> i_mutex lock though...

Look harder. :)

ramfs/tmpfs for a large part just used the generic VFS functions to do
their work since they're page-cache based.  For instance:

static const struct file_operations shmem_file_operations = {
...
        .aio_write      = generic_file_aio_write,

IOW, you need to check beyond mm/shmem.c.

-- Dave

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