From: Matthew Wilcox <willy@infradead.org>
To: "André Almeida" <andrealmeid@collabora.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
Theodore Ts'o <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>,
Jaegeuk Kim <jaegeuk@kernel.org>, Chao Yu <chao@kernel.org>,
krisman@collabora.com, kernel@collabora.com,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-ext4@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net,
Daniel Rosenberg <drosen@google.com>,
Chao Yu <yuchao0@huawei.com>
Subject: Re: [PATCH 1/3] fs/dcache: Add d_clear_dir_neg_dentries()
Date: Sun, 28 Mar 2021 16:07:15 +0100 [thread overview]
Message-ID: <20210328150715.GA33249@casper.infradead.org> (raw)
In-Reply-To: <20210328144356.12866-2-andrealmeid@collabora.com>
On Sun, Mar 28, 2021 at 11:43:54AM -0300, André Almeida wrote:
> +/**
> + * d_clear_dir_neg_dentries - Remove negative dentries in an inode
> + * @dir: Directory to clear negative dentries
> + *
> + * For directories with negative dentries that are becoming case-insensitive
> + * dirs, we need to remove all those negative dentries, otherwise they will
> + * become dangling dentries. During the creation of a new file, if a d_hash
> + * collision happens and the names match in a case-insensitive, the name of
> + * the file will be the name defined at the negative dentry, that can be
> + * different from the specified by the user. To prevent this from happening, we
> + * need to remove all dentries in a directory. Given that the directory must be
> + * empty before we call this function we are sure that all dentries there will
> + * be negative.
> + */
This is quite the landmine of a function. It _assumes_ that the directory
is empty, and clears all dentries in it.
> +void d_clear_dir_neg_dentries(struct inode *dir)
> +{
> + struct dentry *alias, *dentry;
> +
> + hlist_for_each_entry(alias, &dir->i_dentry, d_u.d_alias) {
> + list_for_each_entry(dentry, &alias->d_subdirs, d_child) {
> + d_drop(dentry);
> + dput(dentry);
> + }
I would be happier if it included a check for negativity. d_is_negative()
or maybe this newfangled d_really_is_negative() (i haven't stayed up
to speed on the precise difference between the two)
> + }
> +}
> +EXPORT_SYMBOL(d_clear_dir_neg_dentries);
I'd rather see this _GPL for such an internal thing.
next prev parent reply other threads:[~2021-03-28 15:09 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-28 14:43 [PATCH 0/3] fs: Fix dangling dentries on casefold directories André Almeida
2021-03-28 14:43 ` [PATCH 1/3] fs/dcache: Add d_clear_dir_neg_dentries() André Almeida
2021-03-28 15:07 ` Matthew Wilcox [this message]
2021-03-28 15:49 ` André Almeida
2021-03-28 17:39 ` Al Viro
2021-03-30 1:48 ` Eric Biggers
2021-03-30 12:54 ` André Almeida
2021-03-28 14:43 ` [PATCH 2/3] ext4: Prevent dangling dentries on casefold directories André Almeida
2021-03-28 14:43 ` [PATCH 3/3] f2fs: " André Almeida
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