Messages in this thread | | | From | (Eric W. Biederman) | Date | Thu, 03 Dec 2009 03:56:41 -0800 | Subject | Re: [PATCH 2/2] vfs: force reval on dentry of bind mounted files on FS_REVAL_DOT filesystems |
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Miklos Szeredi <miklos@szeredi.hu> writes:
> On Thu, 03 Dec 2009, Eric W. Biederman wrote: >> > The only worry I have is that this adds an extra branch in a very hot >> > codepath (do_lookup). An error can't be returned, as you note, and >> > for bind mounted directories d_invalidate() will not succeed: the >> > directory is busy, it's referenced by the mount. >> >> Not true. d_mountpoint is false, so d_invalidate can succeed. > > Have a look at the code. d_invalidate() doesn't check for a > mountpoint, it checks the refcount. It needs to keep the directory > dentry hashed if it's in any way reachable other than from the cache > (file descriptor, cwd, mount, etc).
Ah. I thought you were thinking about the mandatory have_submounts() check in dentry->d_op->d_revalidate().
I expect the generic d_invalidate will simply hit the: spin_lock(&dcache_lock); if (d_unhashed(dentry)) { spin_unlock(&dcache_lock); return 0; }
After the distributed filesystem has called d_drop in dentry->d_op->d_revalidate (when appropriate.
Eric
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