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Date: Thu, 12 Nov 2020 10:34:54 +0100
From: Jan Kara <jack@...e.cz>
To: ira.weiny@...el.com
Cc: Jan Kara <jack@...e.com>, linux-ext4@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs/ext2: Use ext2_put_page
On Wed 11-11-20 12:55:30, ira.weiny@...el.com wrote:
> From: Ira Weiny <ira.weiny@...el.com>
>
> There are 3 places in namei.c where the equivalent of ext2_put_page() is
> open coded on a page which was returned from the ext2_get_page() call
> [through the use of ext2_find_entry() and ext2_dotdot()].
>
> Move ext2_get_page() and ext2_put_page() to ext2.h in order to help
> clarify the use of the get/put and then use ext2_put_page() in namei.c
>
> Also add a comment regarding the proper way to release the page returned
> from ext2_find_entry() and ext2_dotdot().
>
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>
Thanks. Good cleanup. I've added it to my tree.
Honza
>
> ---
>
> This was originally part of the kmap_thread() series here:
>
> https://lore.kernel.org/lkml/20201009195033.3208459-37-ira.weiny@intel.com/
>
> But this is really a valid clean up regardless of the
> kmap_thread[local]() changes.
> ---
> fs/ext2/dir.c | 33 ++++++++-------------------------
> fs/ext2/ext2.h | 27 +++++++++++++++++++++++++++
> fs/ext2/namei.c | 15 +++++----------
> 3 files changed, 40 insertions(+), 35 deletions(-)
>
> diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
> index 70355ab6740e..8acd77a66ff4 100644
> --- a/fs/ext2/dir.c
> +++ b/fs/ext2/dir.c
> @@ -66,12 +66,6 @@ static inline unsigned ext2_chunk_size(struct inode *inode)
> return inode->i_sb->s_blocksize;
> }
>
> -static inline void ext2_put_page(struct page *page)
> -{
> - kunmap(page);
> - put_page(page);
> -}
> -
> /*
> * Return the offset into page `page_nr' of the last valid
> * byte in that page, plus one.
> @@ -196,25 +190,6 @@ static bool ext2_check_page(struct page *page, int quiet)
> return false;
> }
>
> -static struct page * ext2_get_page(struct inode *dir, unsigned long n,
> - int quiet)
> -{
> - struct address_space *mapping = dir->i_mapping;
> - struct page *page = read_mapping_page(mapping, n, NULL);
> - if (!IS_ERR(page)) {
> - kmap(page);
> - if (unlikely(!PageChecked(page))) {
> - if (PageError(page) || !ext2_check_page(page, quiet))
> - goto fail;
> - }
> - }
> - return page;
> -
> -fail:
> - ext2_put_page(page);
> - return ERR_PTR(-EIO);
> -}
> -
> /*
> * NOTE! unlike strncmp, ext2_match returns 1 for success, 0 for failure.
> *
> @@ -336,6 +311,8 @@ ext2_readdir(struct file *file, struct dir_context *ctx)
> * returns the page in which the entry was found (as a parameter - res_page),
> * and the entry itself. Page is returned mapped and unlocked.
> * Entry is guaranteed to be valid.
> + *
> + * On Success ext2_put_page() should be called on *res_page.
> */
> struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir,
> const struct qstr *child, struct page **res_page)
> @@ -401,6 +378,12 @@ struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir,
> return de;
> }
>
> +/**
> + * Return the '..' directory entry and the page in which the entry was found
> + * (as a parameter - p).
> + *
> + * On Success ext2_put_page() should be called on *p.
> + */
> struct ext2_dir_entry_2 * ext2_dotdot (struct inode *dir, struct page **p)
> {
> struct page *page = ext2_get_page(dir, 0, 0);
> diff --git a/fs/ext2/ext2.h b/fs/ext2/ext2.h
> index 5136b7289e8d..b4403f96858b 100644
> --- a/fs/ext2/ext2.h
> +++ b/fs/ext2/ext2.h
> @@ -16,6 +16,8 @@
> #include <linux/blockgroup_lock.h>
> #include <linux/percpu_counter.h>
> #include <linux/rbtree.h>
> +#include <linux/mm.h>
> +#include <linux/highmem.h>
>
> /* XXX Here for now... not interested in restructing headers JUST now */
>
> @@ -745,6 +747,31 @@ extern int ext2_delete_entry (struct ext2_dir_entry_2 *, struct page *);
> extern int ext2_empty_dir (struct inode *);
> extern struct ext2_dir_entry_2 * ext2_dotdot (struct inode *, struct page **);
> extern void ext2_set_link(struct inode *, struct ext2_dir_entry_2 *, struct page *, struct inode *, int);
> +static inline void ext2_put_page(struct page *page)
> +{
> + kunmap(page);
> + put_page(page);
> +}
> +
> +static inline struct page * ext2_get_page(struct inode *dir, unsigned long n,
> + int quiet)
> +{
> + struct address_space *mapping = dir->i_mapping;
> + struct page *page = read_mapping_page(mapping, n, NULL);
> + if (!IS_ERR(page)) {
> + kmap(page);
> + if (unlikely(!PageChecked(page))) {
> + if (PageError(page) || !ext2_check_page(page, quiet))
> + goto fail;
> + }
> + }
> + return page;
> +
> +fail:
> + ext2_put_page(page);
> + return ERR_PTR(-EIO);
> +}
> +
>
> /* ialloc.c */
> extern struct inode * ext2_new_inode (struct inode *, umode_t, const struct qstr *);
> diff --git a/fs/ext2/namei.c b/fs/ext2/namei.c
> index 5bf2c145643b..ea980f1e2e99 100644
> --- a/fs/ext2/namei.c
> +++ b/fs/ext2/namei.c
> @@ -389,23 +389,18 @@ static int ext2_rename (struct inode * old_dir, struct dentry * old_dentry,
> if (dir_de) {
> if (old_dir != new_dir)
> ext2_set_link(old_inode, dir_de, dir_page, new_dir, 0);
> - else {
> - kunmap(dir_page);
> - put_page(dir_page);
> - }
> + else
> + ext2_put_page(dir_page);
> inode_dec_link_count(old_dir);
> }
> return 0;
>
>
> out_dir:
> - if (dir_de) {
> - kunmap(dir_page);
> - put_page(dir_page);
> - }
> + if (dir_de)
> + ext2_put_page(dir_page);
> out_old:
> - kunmap(old_page);
> - put_page(old_page);
> + ext2_put_page(old_page);
> out:
> return err;
> }
> --
> 2.28.0.rc0.12.gb6a658bd00c9
>
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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