fs/ext2: Replace kmap() with kmap_local_page()

The k[un]map() calls in ext2_[get|put]_page() are localized to a single
thread.  kmap_local_page() is more efficient.

Replace the kmap/kunmap calls with kmap_local_page()/kunmap_local().
kunmap_local() requires the mapping address so return that address from
ext2_get_page() to be used in ext2_put_page().  This works well because
many of the callers need the address anyway so it is not bad to return
it along with the page.

In addition, kmap_local_page()/kunmap_local() require strict nesting
rules to be followed.

Document the new nesting requirements of ext2_get_page() and
ext2_put_page() as well as the relationship between ext2_get_page(),
ext2_find_entry(), and ext2_dotdot().

Adjust one ext2_put_page() call site in ext2_rename() to ensure the new
nesting requirements are met.

Finally, adjust code style for checkpatch.

To: Jan Kara <jack@suse.com>
Link: https://lore.kernel.org/r/20210329065402.3297092-3-ira.weiny@intel.com
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
index f0b8311..14292db 100644 (file)
--- a/fs/ext2/dir.c
+++ b/fs/ext2/dir.c
@@ -190,13 +190,20 @@ fail:
        return false;
 }
 
+/*
+ * Calls to ext2_get_page()/ext2_put_page() must be nested according to the
+ * rules documented in kmap_local_page()/kunmap_local().
+ *
+ * NOTE: ext2_find_entry() and ext2_dotdot() act as a call to ext2_get_page()
+ * and should be treated as a call to ext2_get_page() for nesting purposes.
+ */
 static struct page * ext2_get_page(struct inode *dir, unsigned long n,
-                                  int quiet)
+                                  int quiet, void **page_addr)
 {
        struct address_space *mapping = dir->i_mapping;
        struct page *page = read_mapping_page(mapping, n, NULL);
        if (!IS_ERR(page)) {
-               kmap(page);
+               *page_addr = kmap_local_page(page);
                if (unlikely(!PageChecked(page))) {
                        if (PageError(page) || !ext2_check_page(page, quiet))
                                goto fail;
@@ -205,7 +212,7 @@ static struct page * ext2_get_page(struct inode *dir, unsigned long n,
        return page;
 
 fail:
-       ext2_put_page(page);
+       ext2_put_page(page, *page_addr);
        return ERR_PTR(-EIO);
 }
 
@@ -276,7 +283,7 @@ ext2_readdir(struct file *file, struct dir_context *ctx)
        for ( ; n < npages; n++, offset = 0) {
                char *kaddr, *limit;
                ext2_dirent *de;
-               struct page *page = ext2_get_page(inode, n, 0);
+               struct page *page = ext2_get_page(inode, n, 0, (void **)&kaddr);
 
                if (IS_ERR(page)) {
                        ext2_error(sb, __func__,
@@ -285,7 +292,6 @@ ext2_readdir(struct file *file, struct dir_context *ctx)
                        ctx->pos += PAGE_SIZE - offset;
                        return PTR_ERR(page);
                }
-               kaddr = page_address(page);
                if (unlikely(need_revalidate)) {
                        if (offset) {
                                offset = ext2_validate_entry(kaddr, offset, chunk_mask);
@@ -300,7 +306,7 @@ ext2_readdir(struct file *file, struct dir_context *ctx)
                        if (de->rec_len == 0) {
                                ext2_error(sb, __func__,
                                        "zero-length directory entry");
-                               ext2_put_page(page);
+                               ext2_put_page(page, kaddr);
                                return -EIO;
                        }
                        if (de->inode) {
@@ -312,13 +318,13 @@ ext2_readdir(struct file *file, struct dir_context *ctx)
                                if (!dir_emit(ctx, de->name, de->name_len,
                                                le32_to_cpu(de->inode),
                                                d_type)) {
-                                       ext2_put_page(page);
+                                       ext2_put_page(page, kaddr);
                                        return 0;
                                }
                        }
                        ctx->pos += ext2_rec_len_from_disk(de->rec_len);
                }
-               ext2_put_page(page);
+               ext2_put_page(page, kaddr);
        }
        return 0;
 }
@@ -332,9 +338,16 @@ ext2_readdir(struct file *file, struct dir_context *ctx)
  * Entry is guaranteed to be valid.
  *
  * On Success ext2_put_page() should be called on *res_page.
+ *
+ * NOTE: Calls to ext2_get_page()/ext2_put_page() must be nested according to
+ * the rules documented in kmap_local_page()/kunmap_local().
+ *
+ * ext2_find_entry() and ext2_dotdot() act as a call to ext2_get_page() and
+ * should be treated as a call to ext2_get_page() for nesting purposes.
  */
 struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir,
-                       const struct qstr *child, struct page **res_page)
+                       const struct qstr *child, struct page **res_page,
+                       void **res_page_addr)
 {
        const char *name = child->name;
        int namelen = child->len;
@@ -344,12 +357,14 @@ struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir,
        struct page *page = NULL;
        struct ext2_inode_info *ei = EXT2_I(dir);
        ext2_dirent * de;
+       void *page_addr;
 
        if (npages == 0)
                goto out;
 
        /* OFFSET_CACHE */
        *res_page = NULL;
+       *res_page_addr = NULL;
 
        start = ei->i_dir_start_lookup;
        if (start >= npages)
@@ -357,25 +372,25 @@ struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir,
        n = start;
        do {
                char *kaddr;
-               page = ext2_get_page(dir, n, 0);
+               page = ext2_get_page(dir, n, 0, &page_addr);
                if (IS_ERR(page))
                        return ERR_CAST(page);
 
-               kaddr = page_address(page);
+               kaddr = page_addr;
                de = (ext2_dirent *) kaddr;
                kaddr += ext2_last_byte(dir, n) - reclen;
                while ((char *) de <= kaddr) {
                        if (de->rec_len == 0) {
                                ext2_error(dir->i_sb, __func__,
                                        "zero-length directory entry");
-                               ext2_put_page(page);
+                               ext2_put_page(page, page_addr);
                                goto out;
                        }
                        if (ext2_match(namelen, name, de))
                                goto found;
                        de = ext2_next_entry(de);
                }
-               ext2_put_page(page);
+               ext2_put_page(page, page_addr);
 
                if (++n >= npages)
                        n = 0;
@@ -393,6 +408,7 @@ out:
 
 found:
        *res_page = page;
+       *res_page_addr = page_addr;
        ei->i_dir_start_lookup = n;
        return de;
 }
@@ -402,15 +418,24 @@ found:
  * (as a parameter - p).
  *
  * On Success ext2_put_page() should be called on *p.
+ *
+ * NOTE: Calls to ext2_get_page()/ext2_put_page() must be nested according to
+ * the rules documented in kmap_local_page()/kunmap_local().
+ *
+ * ext2_find_entry() and ext2_dotdot() act as a call to ext2_get_page() and
+ * should be treated as a call to ext2_get_page() for nesting purposes.
  */
-struct ext2_dir_entry_2 * ext2_dotdot (struct inode *dir, struct page **p)
+struct ext2_dir_entry_2 *ext2_dotdot(struct inode *dir, struct page **p,
+                                    void **pa)
 {
-       struct page *page = ext2_get_page(dir, 0, 0);
+       void *page_addr;
+       struct page *page = ext2_get_page(dir, 0, 0, &page_addr);
        ext2_dirent *de = NULL;
 
        if (!IS_ERR(page)) {
-               de = ext2_next_entry((ext2_dirent *) page_address(page));
+               de = ext2_next_entry((ext2_dirent *) page_addr);
                *p = page;
+               *pa = page_addr;
        }
        return de;
 }
@@ -419,13 +444,14 @@ int ext2_inode_by_name(struct inode *dir, const struct qstr *child, ino_t *ino)
 {
        struct ext2_dir_entry_2 *de;
        struct page *page;
+       void *page_addr;
        
-       de = ext2_find_entry(dir, child, &page);
+       de = ext2_find_entry(dir, child, &page, &page_addr);
        if (IS_ERR(de))
                return PTR_ERR(de);
 
        *ino = le32_to_cpu(de->inode);
-       ext2_put_page(page);
+       ext2_put_page(page, page_addr);
        return 0;
 }
 
@@ -435,10 +461,11 @@ static int ext2_prepare_chunk(struct page *page, loff_t pos, unsigned len)
 }
 
 void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,
-                  struct page *page, struct inode *inode, int update_times)
+                  struct page *page, void *page_addr, struct inode *inode,
+                  int update_times)
 {
        loff_t pos = page_offset(page) +
-                       (char *) de - (char *) page_address(page);
+                       (char *) de - (char *) page_addr;
        unsigned len = ext2_rec_len_from_disk(de->rec_len);
        int err;
 
@@ -466,10 +493,10 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode)
        unsigned reclen = EXT2_DIR_REC_LEN(namelen);
        unsigned short rec_len, name_len;
        struct page *page = NULL;
+       void *page_addr = NULL;
        ext2_dirent * de;
        unsigned long npages = dir_pages(dir);
        unsigned long n;
-       char *kaddr;
        loff_t pos;
        int err;
 
@@ -479,14 +506,15 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode)
         * to protect that region.
         */
        for (n = 0; n <= npages; n++) {
+               char *kaddr;
                char *dir_end;
 
-               page = ext2_get_page(dir, n, 0);
+               page = ext2_get_page(dir, n, 0, &page_addr);
                err = PTR_ERR(page);
                if (IS_ERR(page))
                        goto out;
                lock_page(page);
-               kaddr = page_address(page);
+               kaddr = page_addr;
                dir_end = kaddr + ext2_last_byte(dir, n);
                de = (ext2_dirent *)kaddr;
                kaddr += PAGE_SIZE - reclen;
@@ -517,14 +545,14 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode)
                        de = (ext2_dirent *) ((char *) de + rec_len);
                }
                unlock_page(page);
-               ext2_put_page(page);
+               ext2_put_page(page, page_addr);
        }
        BUG();
        return -EINVAL;
 
 got_it:
        pos = page_offset(page) +
-               (char*)de - (char*)page_address(page);
+               (char *)de - (char *)page_addr;
        err = ext2_prepare_chunk(page, pos, rec_len);
        if (err)
                goto out_unlock;
@@ -544,7 +572,7 @@ got_it:
        mark_inode_dirty(dir);
        /* OFFSET_CACHE */
 out_put:
-       ext2_put_page(page);
+       ext2_put_page(page, page_addr);
 out:
        return err;
 out_unlock:
@@ -641,6 +669,7 @@ fail:
  */
 int ext2_empty_dir (struct inode * inode)
 {
+       void *page_addr = NULL;
        struct page *page = NULL;
        unsigned long i, npages = dir_pages(inode);
        int dir_has_error = 0;
@@ -648,14 +677,14 @@ int ext2_empty_dir (struct inode * inode)
        for (i = 0; i < npages; i++) {
                char *kaddr;
                ext2_dirent * de;
-               page = ext2_get_page(inode, i, dir_has_error);
+               page = ext2_get_page(inode, i, dir_has_error, &page_addr);
 
                if (IS_ERR(page)) {
                        dir_has_error = 1;
                        continue;
                }
 
-               kaddr = page_address(page);
+               kaddr = page_addr;
                de = (ext2_dirent *)kaddr;
                kaddr += ext2_last_byte(inode, i) - EXT2_DIR_REC_LEN(1);
 
@@ -681,12 +710,12 @@ int ext2_empty_dir (struct inode * inode)
                        }
                        de = ext2_next_entry(de);
                }
-               ext2_put_page(page);
+               ext2_put_page(page, page_addr);
        }
        return 1;
 
 not_empty:
-       ext2_put_page(page);
+       ext2_put_page(page, page_addr);
        return 0;
 }
 

diff --git a/fs/ext2/ext2.h b/fs/ext2/ext2.h
index 3309fb2..ad01ef9 100644 (file)
--- a/fs/ext2/ext2.h
+++ b/fs/ext2/ext2.h
@@ -742,14 +742,16 @@ extern int ext2_add_link (struct dentry *, struct inode *);
 extern int ext2_inode_by_name(struct inode *dir,
                              const struct qstr *child, ino_t *ino);
 extern int ext2_make_empty(struct inode *, struct inode *);
-extern struct ext2_dir_entry_2 * ext2_find_entry (struct inode *,const struct qstr *, struct page **);
+extern struct ext2_dir_entry_2 *ext2_find_entry(struct inode *, const struct qstr *,
+                                               struct page **, void **res_page_addr);
 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)
+extern struct ext2_dir_entry_2 *ext2_dotdot(struct inode *dir, struct page **p, void **pa);
+extern void ext2_set_link(struct inode *, struct ext2_dir_entry_2 *, struct page *, void *,
+                         struct inode *, int);
+static inline void ext2_put_page(struct page *page, void *page_addr)
 {
-       kunmap(page);
+       kunmap_local(page_addr);
        put_page(page);
 }
 

diff --git a/fs/ext2/namei.c b/fs/ext2/namei.c
index 7af9ab3..c45e175 100644 (file)
--- a/fs/ext2/namei.c
+++ b/fs/ext2/namei.c
@@ -281,20 +281,21 @@ static int ext2_unlink(struct inode * dir, struct dentry *dentry)
        struct inode * inode = d_inode(dentry);
        struct ext2_dir_entry_2 * de;
        struct page * page;
+       void *page_addr;
        int err;
 
        err = dquot_initialize(dir);
        if (err)
                goto out;
 
-       de = ext2_find_entry(dir, &dentry->d_name, &page);
+       de = ext2_find_entry(dir, &dentry->d_name, &page, &page_addr);
        if (IS_ERR(de)) {
                err = PTR_ERR(de);
                goto out;
        }
 
        err = ext2_delete_entry (de, page);
-       ext2_put_page(page);
+       ext2_put_page(page, page_addr);
        if (err)
                goto out;
 
@@ -329,8 +330,10 @@ static int ext2_rename (struct user_namespace * mnt_userns,
        struct inode * old_inode = d_inode(old_dentry);
        struct inode * new_inode = d_inode(new_dentry);
        struct page * dir_page = NULL;
+       void *dir_page_addr;
        struct ext2_dir_entry_2 * dir_de = NULL;
        struct page * old_page;
+       void *old_page_addr;
        struct ext2_dir_entry_2 * old_de;
        int err;
 
@@ -345,7 +348,8 @@ static int ext2_rename (struct user_namespace * mnt_userns,
        if (err)
                goto out;
 
-       old_de = ext2_find_entry(old_dir, &old_dentry->d_name, &old_page);
+       old_de = ext2_find_entry(old_dir, &old_dentry->d_name, &old_page,
+                                &old_page_addr);
        if (IS_ERR(old_de)) {
                err = PTR_ERR(old_de);
                goto out;
@@ -353,12 +357,13 @@ static int ext2_rename (struct user_namespace * mnt_userns,
 
        if (S_ISDIR(old_inode->i_mode)) {
                err = -EIO;
-               dir_de = ext2_dotdot(old_inode, &dir_page);
+               dir_de = ext2_dotdot(old_inode, &dir_page, &dir_page_addr);
                if (!dir_de)
                        goto out_old;
        }
 
        if (new_inode) {
+               void *page_addr;
                struct page *new_page;
                struct ext2_dir_entry_2 *new_de;
 
@@ -366,13 +371,14 @@ static int ext2_rename (struct user_namespace * mnt_userns,
                if (dir_de && !ext2_empty_dir (new_inode))
                        goto out_dir;
 
-               new_de = ext2_find_entry(new_dir, &new_dentry->d_name, &new_page);
+               new_de = ext2_find_entry(new_dir, &new_dentry->d_name,
+                                        &new_page, &page_addr);
                if (IS_ERR(new_de)) {
                        err = PTR_ERR(new_de);
                        goto out_dir;
                }
-               ext2_set_link(new_dir, new_de, new_page, old_inode, 1);
-               ext2_put_page(new_page);
+               ext2_set_link(new_dir, new_de, new_page, page_addr, old_inode, 1);
+               ext2_put_page(new_page, page_addr);
                new_inode->i_ctime = current_time(new_inode);
                if (dir_de)
                        drop_nlink(new_inode);
@@ -392,24 +398,25 @@ static int ext2_rename (struct user_namespace * mnt_userns,
        old_inode->i_ctime = current_time(old_inode);
        mark_inode_dirty(old_inode);
 
-       ext2_delete_entry (old_de, old_page);
-       ext2_put_page(old_page);
+       ext2_delete_entry(old_de, old_page);
 
        if (dir_de) {
                if (old_dir != new_dir)
-                       ext2_set_link(old_inode, dir_de, dir_page, new_dir, 0);
+                       ext2_set_link(old_inode, dir_de, dir_page,
+                                     dir_page_addr, new_dir, 0);
 
-               ext2_put_page(dir_page);
+               ext2_put_page(dir_page, dir_page_addr);
                inode_dec_link_count(old_dir);
        }
-       return 0;
 
+       ext2_put_page(old_page, old_page_addr);
+       return 0;
 
 out_dir:
        if (dir_de)
-               ext2_put_page(dir_page);
+               ext2_put_page(dir_page, dir_page_addr);
 out_old:
-       ext2_put_page(old_page);
+       ext2_put_page(old_page, old_page_addr);
 out:
        return err;
 }