[PATCH] ext3: ext3_symlink should use GFP_NOFS allocations inside

This patch fixes illegal __GFP_FS allocation inside ext3 transaction in
ext3_symlink().  Such allocation may re-enter ext3 code from
try_to_free_pages.  But JBD/ext3 code keeps a pointer to current journal
handle in task_struct and, hence, is not reentrable.

This bug led to "Assertion failure in journal_dirty_metadata()" messages.

http://bugzilla.openvz.org/show_bug.cgi?id=115

Signed-off-by: Andrey Savochkin <saw@saw.sw.com.sg>
Signed-off-by: Kirill Korotaev <dev@openvz.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 15 insertions, 3 deletions

diff --git a/fs/ext3/namei.c b/fs/ext3/namei.c
index 8bd8ac077704..b8f5cd1e540d 100644
--- a/fs/ext3/namei.c
+++ b/fs/ext3/namei.c
@@ -2141,7 +2141,8 @@ retry:
                  * We have a transaction open.  All is sweetness.  It also sets
                  * i_size in generic_commit_write().
                  */
-                err = page_symlink(inode, symname, l);
+                err = __page_symlink(inode, symname, l,
+                                mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS);
                 if (err) {
                         ext3_dec_count(handle, inode);
                         ext3_mark_inode_dirty(handle, inode);
diff --git a/fs/namei.c b/fs/namei.c
index 557dcf395ca1..8dc2b038d5d9 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2613,13 +2613,15 @@ void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
         }
 }
 
-int page_symlink(struct inode *inode, const char *symname, int len)
+int __page_symlink(struct inode *inode, const char *symname, int len,
+                gfp_t gfp_mask)
 {
         struct address_space *mapping = inode->i_mapping;
-        struct page *page = grab_cache_page(mapping, 0);
+        struct page *page;
         int err = -ENOMEM;
         char *kaddr;
 
+        page = find_or_create_page(mapping, 0, gfp_mask);
         if (!page)
                 goto fail;
         err = mapping->a_ops->prepare_write(NULL, page, 0, len-1);
@@ -2654,6 +2656,12 @@ fail:
         return err;
 }
 
+int page_symlink(struct inode *inode, const char *symname, int len)
+{
+        return __page_symlink(inode, symname, len,
+                        mapping_gfp_mask(inode->i_mapping));
+}
+
 struct inode_operations page_symlink_inode_operations = {
         .readlink       = generic_readlink,
         .follow_link    = page_follow_link_light,
@@ -2672,6 +2680,7 @@ EXPORT_SYMBOL(lookup_one_len);
 EXPORT_SYMBOL(page_follow_link_light);
 EXPORT_SYMBOL(page_put_link);
 EXPORT_SYMBOL(page_readlink);
+EXPORT_SYMBOL(__page_symlink);
 EXPORT_SYMBOL(page_symlink);
 EXPORT_SYMBOL(page_symlink_inode_operations);
 EXPORT_SYMBOL(path_lookup);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 51c0c93bdf93..128d0082522c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1664,6 +1664,8 @@ extern int vfs_follow_link(struct nameidata *, const char *);
 extern int page_readlink(struct dentry *, char __user *, int);
 extern void *page_follow_link_light(struct dentry *, struct nameidata *);
 extern void page_put_link(struct dentry *, struct nameidata *, void *);
+extern int __page_symlink(struct inode *inode, const char *symname, int len,
+                gfp_t gfp_mask);
 extern int page_symlink(struct inode *inode, const char *symname, int len);
 extern struct inode_operations page_symlink_inode_operations;
 extern int generic_readlink(struct dentry *, char __user *, int);