don't put symlink bodies in pagecache into highmem

kmap() in page_follow_link_light() needed to go - allowing to hold
an arbitrary number of kmaps for long is a great way to deadlocking
the system.

new helper (inode_nohighmem(inode)) needs to be used for pagecache
symlinks inodes; done for all in-tree cases.  page_follow_link_light()
instrumented to yell about anything missed.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 3 insertions, 6 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 4bae5cbfaa85..2808958e6c67 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4527,7 +4527,8 @@ static const char *page_getlink(struct dentry * dentry, void **cookie)
         if (IS_ERR(page))
                 return (char*)page;
         *cookie = page;
-        kaddr = kmap(page);
+        BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM);
+        kaddr = page_address(page);
         nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
         return kaddr;
 }
@@ -4541,7 +4542,6 @@ EXPORT_SYMBOL(page_follow_link_light);
 void page_put_link(struct inode *unused, void *cookie)
 {
         struct page *page = cookie;
-        kunmap(page);
         page_cache_release(page);
 }
 EXPORT_SYMBOL(page_put_link);
@@ -4565,7 +4565,6 @@ int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
         struct page *page;
         void *fsdata;
         int err;
-        char *kaddr;
         unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
         if (nofs)
                 flags |= AOP_FLAG_NOFS;
@@ -4576,9 +4575,7 @@ retry:
         if (err)
                 goto fail;
 
-        kaddr = kmap_atomic(page);
-        memcpy(kaddr, symname, len-1);
-        kunmap_atomic(kaddr);
+        memcpy(page_address(page), symname, len-1);
 
         err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
                                                         page, fsdata);