ext4: fix races between page faults and hole punching

[karo-tx-linux.git] / fs / ext4 / ext4.h

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index d4156e1c128d09d9f4e0d324d97da79136d45fbf..89df9f55595b7c978d5f3a82cbba1c9cf00044f6 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -933,6 +933,15 @@ struct ext4_inode_info {
         * by other means, so we have i_data_sem.
         */
        struct rw_semaphore i_data_sem;
+       /*
+        * i_mmap_sem is for serializing page faults with truncate / punch hole
+        * operations. We have to make sure that new page cannot be faulted in
+        * a section of the inode that is being punched. We cannot easily use
+        * i_data_sem for this since we need protection for the whole punch
+        * operation and i_data_sem ranks below transaction start so we have
+        * to occasionally drop it.
+        */
+       struct rw_semaphore i_mmap_sem;
        struct inode vfs_inode;
        struct jbd2_inode *jinode;
 
@@ -2507,6 +2516,7 @@ extern int ext4_chunk_trans_blocks(struct inode *, int nrblocks);
 extern int ext4_zero_partial_blocks(handle_t *handle, struct inode *inode,
                             loff_t lstart, loff_t lend);
 extern int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf);
+extern int ext4_filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf);
 extern qsize_t *ext4_get_reserved_space(struct inode *inode);
 extern void ext4_da_update_reserve_space(struct inode *inode,
                                        int used, int quota_claim);