linux-kernel - Re: [PATCH v2] fs/dcache.c: avoid soft-lockup in dput()

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Message-ID: <20160916121023.GX2356@ZenIV.linux.org.uk>
Date:   Fri, 16 Sep 2016 13:10:23 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Vaishali Thakkar <vaishali.thakkar@...cle.com>
Cc:     Wei Fang <fangwei1@...wei.com>, linux-fsdevel@...r.kernel.org,
        akpm@...ux-foundation.org, jack@...e.com, axboe@...nel.dk,
        tj@...nel.org, linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2] fs/dcache.c: avoid soft-lockup in dput()

On Fri, Sep 16, 2016 at 01:19:19PM +0530, Vaishali Thakkar wrote:

> Hi,
> 
> Just a question regarding this change. As after this change
> dput() is sleepable, is it still safe to use if under the
> spinlock in the function d_prune_aliases?

It has always been sleepable and it wouldn't have been safe to use
under spinlocks.  Which d_prune_aliases() does not do - __dentry_kill()
is called with dentry, its parent and its inode (if present) all locked and
it drops all those locks before returning.