From: Al Viro <viro@zeniv.linux.org.uk>
To: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
Cc: Evgeniy Dushistov <dushistov@mail.ru>,
Ira Weiny <ira.weiny@intel.com>,
linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 3/3] fs/ufs: Replace kmap() with kmap_local_page()
Date: Sun, 11 Dec 2022 22:39:44 +0000 [thread overview]
Message-ID: <Y5ZcMPzPG9h6C9eh@ZenIV> (raw)
In-Reply-To: <20221211213111.30085-4-fmdefrancesco@gmail.com>
On Sun, Dec 11, 2022 at 10:31:11PM +0100, Fabio M. De Francesco wrote:
> +/*
> + * Calls to ufs_get_page()/ufs_put_page() must be nested according to the
> + * rules documented in kmap_local_page()/kunmap_local().
> + *
> + * NOTE: ufs_find_entry() and ufs_dotdot() act as calls to ufs_get_page()
> + * and must be treated accordingly for nesting purposes.
> + */
> static void *ufs_get_page(struct inode *dir, unsigned long n, struct page **page)
> {
> + char *kaddr;
> +
> struct address_space *mapping = dir->i_mapping;
> *page = read_mapping_page(mapping, n, NULL);
> if (!IS_ERR(*page)) {
> - kmap(*page);
> + kmap_local_page(*page);
> if (unlikely(!PageChecked(*page))) {
> - if (!ufs_check_page(*page))
> + if (!ufs_check_page(*page, kaddr))
Er... Building the patched tree is occasionally useful.
Here kaddr is obviously uninitialized and compiler would've
probably caught that.
And return value of kmap_local_page() is lost, which
is related to the previous issue ;-)
> goto fail;
> }
> }
> - return page;
> + return *page;
Hell, no. Callers expect the pointer to the first byte of
your page. What it should return is kaddr.
> @@ -388,7 +406,8 @@ int ufs_add_link(struct dentry *dentry, struct inode *inode)
> mark_inode_dirty(dir);
> /* OFFSET_CACHE */
> out_put:
> - ufs_put_page(page);
> + ufs_put_page(page, kaddr);
> + return 0;
> out_unlock:
> unlock_page(page);
> goto out_put;
That can't be right. Places like
if (err)
goto out_unlock;
do not expect err to be lost. You end up returning 0 now. Something strange
happened here (in the previous commit, perhaps?)
next prev parent reply other threads:[~2022-12-11 22:39 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-11 21:31 [PATCH 0/3] fs/ufs: replace kmap() with kmap_local_page() Fabio M. De Francesco
2022-12-11 21:31 ` [PATCH 1/3] fs/ufs: Use the offset_in_page() helper Fabio M. De Francesco
2022-12-11 21:31 ` [PATCH 2/3] fs/ufs: Change the signature of ufs_get_page() Fabio M. De Francesco
2022-12-11 22:29 ` Al Viro
2022-12-11 23:56 ` Fabio M. De Francesco
2022-12-11 22:42 ` Al Viro
2022-12-12 20:08 ` Fabio M. De Francesco
2022-12-11 21:31 ` [PATCH 3/3] fs/ufs: Replace kmap() with kmap_local_page() Fabio M. De Francesco
2022-12-11 22:39 ` Al Viro [this message]
2022-12-12 0:14 ` Fabio M. De Francesco
2022-12-12 0:52 ` kernel test robot
2022-12-12 1:07 ` Al Viro
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