Make sure that highmem pages are not added to symlink page cache
inode_nohighmem() is sufficient to make sure that page_get_link()
won't try to allocate a highmem page. Moreover, it is sufficient
to make sure that page_symlink/__page_symlink won't do the same
thing. However, any filesystem that manually preseeds the symlink's
page cache upon symlink(2) needs to make sure that the page it
inserts there won't be a highmem one.
Fortunately, only nfs and shmem have run afoul of that...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index 0f88e60..f1b87d8 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -508,7 +508,11 @@
[mandatory]
any symlink that might use page_follow_link_light/page_put_link() must
have inode_nohighmem(inode) called before anything might start playing with
- its pagecache.
+ its pagecache. No highmem pages should end up in the pagecache of such
+ symlinks. That includes any preseeding that might be done during symlink
+ creation. __page_symlink() will honour the mapping gfp flags, so once
+ you've done inode_nohighmem() it's safe to use, but if you allocate and
+ insert the page manually, make sure to use the right gfp flags.
--
[mandatory]
->follow_link() is replaced with ->get_link(); same API, except that
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index ce5a218..8a05309 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1894,15 +1894,14 @@
attr.ia_mode = S_IFLNK | S_IRWXUGO;
attr.ia_valid = ATTR_MODE;
- page = alloc_page(GFP_HIGHUSER);
+ page = alloc_page(GFP_USER);
if (!page)
return -ENOMEM;
- kaddr = kmap_atomic(page);
+ kaddr = page_address(page);
memcpy(kaddr, symname, pathlen);
if (pathlen < PAGE_SIZE)
memset(kaddr + pathlen, 0, PAGE_SIZE - pathlen);
- kunmap_atomic(kaddr);
trace_nfs_symlink_enter(dir, dentry);
error = NFS_PROTO(dir)->symlink(dir, dentry, page, pathlen, &attr);
diff --git a/mm/shmem.c b/mm/shmem.c
index 5813b7f..642471b 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2469,6 +2469,7 @@
inode->i_op = &shmem_short_symlink_operations;
inode->i_link = info->symlink;
} else {
+ inode_nohighmem(inode);
error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
if (error) {
iput(inode);
@@ -2476,7 +2477,6 @@
}
inode->i_mapping->a_ops = &shmem_aops;
inode->i_op = &shmem_symlink_inode_operations;
- inode_nohighmem(inode);
memcpy(page_address(page), symname, len);
SetPageUptodate(page);
set_page_dirty(page);