From: "Darrick J. Wong" Subject: Re: [RFC PATCH] ext4: increase the protection of drop nlink and ext4 inode destroy Date: Thu, 5 Jan 2017 09:38:38 -0800 Message-ID: <20170105173838.GC14021@birch.djwong.org> References: <1482755657-28791-1-git-send-email-yi.zhang@huawei.com> <141922.1483225153@turing-police.cc.vt.edu> <10c6fa5d-a7bb-a87c-11ad-8d30230a6075@huawei.com> <20170104215424.GB14021@birch.djwong.org> <20170104233550.oy7nzc3rxppmejbk@thunk.org> <5505c121-8038-1b72-423a-42f36257e959@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Theodore Ts'o" , Valdis.Kletnieks@vt.edu, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, adilger.kernel@dilger.ca To: "zhangyi (F)" Return-path: Content-Disposition: inline In-Reply-To: <5505c121-8038-1b72-423a-42f36257e959@huawei.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Thu, Jan 05, 2017 at 03:24:14PM +0800, zhangyi (F) wrote: > > On 2017/1/5 7:35, Theodore Ts'o wrote: > > > > So how exactly how did we get into this state? When we read the inode > > into memory, if i_nlink is zero, we declare the file system as > > corrupted immediately. > > > > So I assume this is happening the on-disk i_links_count (which is read > > into inode->i_nlink) was too low. So I think the way we should be > > handling this is in unlink and rename, before we let i_nlink drop to D'oh, /me failed to notice the patch was against fs/inode.c, not fs/ext4/inode.c. Sorry for the noise. > > zero, we need to check to see if there are other dcache entries > > pointing at the inode. If so, we need to call ext4_error(), and in > > the errors=continue case, return EFSCORRUPTED (aka EUCLEAN). > > > > diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c > --- a/fs/ext4/namei.c > +++ b/fs/ext4/namei.c > @@ -3662,6 +3662,11 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry, > } > > if (new.inode) { > + if (new.inode->i_nlink == 0) { > + ext4_warning_inode(new.inode, "Removing file '%.*s' with no links", > + new.dentry->d_name.len, new.dentry->d_name.name); > + set_nlink(new.inode, 1); Not sure we need to dump the dentry d_name, but I guess it can't hurt. > + } > ext4_dec_count(handle, new.inode); > new.inode->i_ctime = ext4_current_time(new.inode); > } > > Because the filesystem have many errors, and the reason of i_nlink becomes > zero is unknown, the on-disk i_links_count was too low may be one reason. I > think we can add i_nlink check in ext4_rename just like ext4_unlink did, it > can avoid inversion under any case. Er... yes, you could add the same hunk to ext4_unlink. --D > > > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html