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authorAl Viro <viro@zeniv.linux.org.uk>2016-04-22 15:06:44 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2016-05-02 19:47:25 -0400
commitbe5b82dbfec2a900925da4437af3c60b61f4c53d (patch)
treea65508f3456f623f51215581e3b00529a9c20ee7 /fs/exofs
parentb9e1d435fdf4ae0b925070d44b65d608f2707688 (diff)
make ext2_get_page() and friends work without external serialization
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 <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/exofs')
-rw-r--r--fs/exofs/dir.c14
1 files changed, 7 insertions, 7 deletions
diff --git a/fs/exofs/dir.c b/fs/exofs/dir.c
index 547b93cbea63..a7661aaead9a 100644
--- a/fs/exofs/dir.c
+++ b/fs/exofs/dir.c
@@ -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);
@@ -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]: "
@@ -150,8 +150,8 @@ Eend:
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)
@@ -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;