1 files changed, 57 insertions, 9 deletions

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 113837e7ba98..0d24ebcd7c9e 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -209,15 +209,18 @@ static int ext4_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
         int result;
         handle_t *handle = NULL;
-        struct super_block *sb = file_inode(vma->vm_file)->i_sb;
+        struct inode *inode = file_inode(vma->vm_file);
+        struct super_block *sb = inode->i_sb;
         bool write = vmf->flags & FAULT_FLAG_WRITE;
 
         if (write) {
                 sb_start_pagefault(sb);
                 file_update_time(vma->vm_file);
+                down_read(&EXT4_I(inode)->i_mmap_sem);
                 handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE,
                                                 EXT4_DATA_TRANS_BLOCKS(sb));
-        }
+        } else
+                down_read(&EXT4_I(inode)->i_mmap_sem);
 
         if (IS_ERR(handle))
                 result = VM_FAULT_SIGBUS;
@@ -228,8 +231,10 @@ static int ext4_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
         if (write) {
                 if (!IS_ERR(handle))
                         ext4_journal_stop(handle);
+                up_read(&EXT4_I(inode)->i_mmap_sem);
                 sb_end_pagefault(sb);
-        }
+        } else
+                up_read(&EXT4_I(inode)->i_mmap_sem);
 
         return result;
 }
@@ -246,10 +251,12 @@ static int ext4_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
         if (write) {
                 sb_start_pagefault(sb);
                 file_update_time(vma->vm_file);
+                down_read(&EXT4_I(inode)->i_mmap_sem);
                 handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE,
                                 ext4_chunk_trans_blocks(inode,
                                                         PMD_SIZE / PAGE_SIZE));
-        }
+        } else
+                down_read(&EXT4_I(inode)->i_mmap_sem);
 
         if (IS_ERR(handle))
                 result = VM_FAULT_SIGBUS;
@@ -260,30 +267,71 @@ static int ext4_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
         if (write) {
                 if (!IS_ERR(handle))
                         ext4_journal_stop(handle);
+                up_read(&EXT4_I(inode)->i_mmap_sem);
                 sb_end_pagefault(sb);
-        }
+        } else
+                up_read(&EXT4_I(inode)->i_mmap_sem);
 
         return result;
 }
 
 static int ext4_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
-        return dax_mkwrite(vma, vmf, ext4_get_block_dax,
-                                ext4_end_io_unwritten);
+        int err;
+        struct inode *inode = file_inode(vma->vm_file);
+
+        sb_start_pagefault(inode->i_sb);
+        file_update_time(vma->vm_file);
+        down_read(&EXT4_I(inode)->i_mmap_sem);
+        err = __dax_mkwrite(vma, vmf, ext4_get_block_dax,
+                            ext4_end_io_unwritten);
+        up_read(&EXT4_I(inode)->i_mmap_sem);
+        sb_end_pagefault(inode->i_sb);
+
+        return err;
+}
+
+/*
+ * Handle write fault for VM_MIXEDMAP mappings. Similarly to ext4_dax_mkwrite()
+ * handler we check for races agaist truncate. Note that since we cycle through
+ * i_mmap_sem, we are sure that also any hole punching that began before we
+ * were called is finished by now and so if it included part of the file we
+ * are working on, our pte will get unmapped and the check for pte_same() in
+ * wp_pfn_shared() fails. Thus fault gets retried and things work out as
+ * desired.
+ */
+static int ext4_dax_pfn_mkwrite(struct vm_area_struct *vma,
+                                struct vm_fault *vmf)
+{
+        struct inode *inode = file_inode(vma->vm_file);
+        struct super_block *sb = inode->i_sb;
+        int ret = VM_FAULT_NOPAGE;
+        loff_t size;
+
+        sb_start_pagefault(sb);
+        file_update_time(vma->vm_file);
+        down_read(&EXT4_I(inode)->i_mmap_sem);
+        size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
+        if (vmf->pgoff >= size)
+                ret = VM_FAULT_SIGBUS;
+        up_read(&EXT4_I(inode)->i_mmap_sem);
+        sb_end_pagefault(sb);
+
+        return ret;
 }
 
 static const struct vm_operations_struct ext4_dax_vm_ops = {
         .fault          = ext4_dax_fault,
         .pmd_fault      = ext4_dax_pmd_fault,
         .page_mkwrite   = ext4_dax_mkwrite,
-        .pfn_mkwrite    = dax_pfn_mkwrite,
+        .pfn_mkwrite    = ext4_dax_pfn_mkwrite,
 };
 #else
 #define ext4_dax_vm_ops ext4_file_vm_ops
 #endif
 
 static const struct vm_operations_struct ext4_file_vm_ops = {
-        .fault          = filemap_fault,
+        .fault          = ext4_filemap_fault,
         .map_pages      = filemap_map_pages,
         .page_mkwrite   = ext4_page_mkwrite,
 };