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

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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>
This commit is contained in:
Ira Weiny 2021-03-28 23:54:02 -07:00 committed by Jan Kara
parent e2ebb12304
commit 782b76d7ab
3 changed files with 87 additions and 49 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

89
fs/ext2/dir.c
View File

@ -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;
}

12
fs/ext2/ext2.h
View File

@ -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);
}

35
fs/ext2/namei.c
View File

@ -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;
}