Skip to content

Commit

Permalink
make ext2_get_page() and friends work without external serialization
Browse files Browse the repository at this point in the history 
Right now ext2_get_page() (and its analogues in a bunch of other filesystems)
relies upon the directory being locked - the way it sets and tests Checked and
Error bits would be racy without that.  Switch to a slightly different scheme,
_not_ setting Checked in case of failure.  That way the logics becomes
	if Checked => OK
	else if Error => fail
	else if !validate => fail
	else => OK
with validation setting Checked or Error on success and failure resp. and
returning which one had happened.  Equivalent to the current logics, but unlike
the current logics not sensitive to the order of set_bit, test_bit getting
reordered by CPU, etc.

Signed-off-by: Al Viro <[email protected]>
  • Loading branch information
Al Viro committed May 2, 2016
1 parent b9e1d43 commit be5b82d
Show file tree
Hide file tree
Showing 5 changed files with 35 additions and 35 deletions.
14 changes: 7 additions & 7 deletions fs/afs/dir.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -128,7 +128,7 @@ struct afs_lookup_cookie {
/*
* check that a directory page is valid
*/
static inline void afs_dir_check_page(struct inode *dir, struct page *page)
static inline bool afs_dir_check_page(struct inode *dir, struct page *page)
{
struct afs_dir_page *dbuf;
loff_t latter;
Expand Down Expand Up @@ -168,11 +168,11 @@ static inline void afs_dir_check_page(struct inode *dir, struct page *page)
}

SetPageChecked(page);
return;
return true;

error:
SetPageChecked(page);
SetPageError(page);
return false;
}

/*
Expand All @@ -196,10 +196,10 @@ static struct page *afs_dir_get_page(struct inode *dir, unsigned long index,
page = read_cache_page(dir->i_mapping, index, afs_page_filler, key);
if (!IS_ERR(page)) {
kmap(page);
if (!PageChecked(page))
afs_dir_check_page(dir, page);
if (PageError(page))
goto fail;
if (unlikely(!PageChecked(page))) {
if (PageError(page) || !afs_dir_check_page(dir, page))
goto fail;
}
}
return page;

Expand Down
14 changes: 7 additions & 7 deletions fs/exofs/dir.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -79,7 +79,7 @@ static int exofs_commit_chunk(struct page *page, loff_t pos, unsigned len)
return err;
}

static void exofs_check_page(struct page *page)
static bool exofs_check_page(struct page *page)
{
struct inode *dir = page->mapping->host;
unsigned chunk_size = exofs_chunk_size(dir);
Expand Down Expand Up @@ -114,7 +114,7 @@ static void exofs_check_page(struct page *page)
goto Eend;
out:
SetPageChecked(page);
return;
return true;

Ebadsize:
EXOFS_ERR("ERROR [exofs_check_page]: "
Expand Down Expand Up @@ -150,8 +150,8 @@ static void exofs_check_page(struct page *page)
dir->i_ino, (page->index<<PAGE_SHIFT)+offs,
_LLU(le64_to_cpu(p->inode_no)));
fail:
SetPageChecked(page);
SetPageError(page);
return false;
}

static struct page *exofs_get_page(struct inode *dir, unsigned long n)
Expand All @@ -161,10 +161,10 @@ static struct page *exofs_get_page(struct inode *dir, unsigned long n)

if (!IS_ERR(page)) {
kmap(page);
if (!PageChecked(page))
exofs_check_page(page);
if (PageError(page))
goto fail;
if (unlikely(!PageChecked(page))) {
if (PageError(page) || !exofs_check_page(page))
goto fail;
}
}
return page;

Expand Down
14 changes: 7 additions & 7 deletions fs/ext2/dir.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -110,7 +110,7 @@ static int ext2_commit_chunk(struct page *page, loff_t pos, unsigned len)
return err;
}

static void ext2_check_page(struct page *page, int quiet)
static bool ext2_check_page(struct page *page, int quiet)
{
struct inode *dir = page->mapping->host;
struct super_block *sb = dir->i_sb;
Expand Down Expand Up @@ -148,7 +148,7 @@ static void ext2_check_page(struct page *page, int quiet)
goto Eend;
out:
SetPageChecked(page);
return;
return true;

/* Too bad, we had an error */

Expand Down Expand Up @@ -190,8 +190,8 @@ static void ext2_check_page(struct page *page, int quiet)
(unsigned long) le32_to_cpu(p->inode));
}
fail:
SetPageChecked(page);
SetPageError(page);
return false;
}

static struct page * ext2_get_page(struct inode *dir, unsigned long n,
Expand All @@ -201,10 +201,10 @@ static struct page * ext2_get_page(struct inode *dir, unsigned long n,
struct page *page = read_mapping_page(mapping, n, NULL);
if (!IS_ERR(page)) {
kmap(page);
if (!PageChecked(page))
ext2_check_page(page, quiet);
if (PageError(page))
goto fail;
if (unlikely(!PageChecked(page))) {
if (PageError(page) || !ext2_check_page(page, quiet))
goto fail;
}
}
return page;

Expand Down
14 changes: 7 additions & 7 deletions fs/nilfs2/dir.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -102,7 +102,7 @@ static void nilfs_commit_chunk(struct page *page,
unlock_page(page);
}

static void nilfs_check_page(struct page *page)
static bool nilfs_check_page(struct page *page)
{
struct inode *dir = page->mapping->host;
struct super_block *sb = dir->i_sb;
Expand Down Expand Up @@ -137,7 +137,7 @@ static void nilfs_check_page(struct page *page)
goto Eend;
out:
SetPageChecked(page);
return;
return true;

/* Too bad, we had an error */

Expand Down Expand Up @@ -173,8 +173,8 @@ static void nilfs_check_page(struct page *page)
dir->i_ino, (page->index<<PAGE_SHIFT)+offs,
(unsigned long) le64_to_cpu(p->inode));
fail:
SetPageChecked(page);
SetPageError(page);
return false;
}

static struct page *nilfs_get_page(struct inode *dir, unsigned long n)
Expand All @@ -184,10 +184,10 @@ static struct page *nilfs_get_page(struct inode *dir, unsigned long n)

if (!IS_ERR(page)) {
kmap(page);
if (!PageChecked(page))
nilfs_check_page(page);
if (PageError(page))
goto fail;
if (unlikely(!PageChecked(page))) {
if (PageError(page) || !nilfs_check_page(page))
goto fail;
}
}
return page;

Expand Down
14 changes: 7 additions & 7 deletions fs/ufs/dir.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -105,7 +105,7 @@ void ufs_set_link(struct inode *dir, struct ufs_dir_entry *de,
}


static void ufs_check_page(struct page *page)
static bool ufs_check_page(struct page *page)
{
struct inode *dir = page->mapping->host;
struct super_block *sb = dir->i_sb;
Expand Down Expand Up @@ -143,7 +143,7 @@ static void ufs_check_page(struct page *page)
goto Eend;
out:
SetPageChecked(page);
return;
return true;

/* Too bad, we had an error */

Expand Down Expand Up @@ -180,8 +180,8 @@ static void ufs_check_page(struct page *page)
"offset=%lu",
dir->i_ino, (page->index<<PAGE_SHIFT)+offs);
fail:
SetPageChecked(page);
SetPageError(page);
return false;
}

static struct page *ufs_get_page(struct inode *dir, unsigned long n)
Expand All @@ -190,10 +190,10 @@ static struct page *ufs_get_page(struct inode *dir, unsigned long n)
struct page *page = read_mapping_page(mapping, n, NULL);
if (!IS_ERR(page)) {
kmap(page);
if (!PageChecked(page))
ufs_check_page(page);
if (PageError(page))
goto fail;
if (unlikely(!PageChecked(page))) {
if (PageError(page) || !ufs_check_page(page))
goto fail;
}
}
return page;

Expand Down

0 comments on commit be5b82d

Please sign in to comment.