ext4: Simplify DAX fault path

Now that dax_iomap_fault() calls ->iomap_begin() without entry lock, we
can use transaction starting in ext4_iomap_begin() and thus simplify
ext4_dax_fault(). It also provides us proper retries in case of ENOSPC.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index b5f184493c57b0fd91cfc5f6c0633577ce770884..d663d3d7c81cb7fdff0f33f1903e9ed4d1f77f9a 100644 (file)
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -258,7 +258,6 @@ out:
 static int ext4_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
        int result;
-       handle_t *handle = NULL;
        struct inode *inode = file_inode(vma->vm_file);
        struct super_block *sb = inode->i_sb;
        bool write = vmf->flags & FAULT_FLAG_WRITE;
@@ -266,24 +265,12 @@ static int ext4_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
        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;
-       else
-               result = dax_iomap_fault(vma, vmf, &ext4_iomap_ops);
-
-       if (write) {
-               if (!IS_ERR(handle))
-                       ext4_journal_stop(handle);
-               up_read(&EXT4_I(inode)->i_mmap_sem);
+       }
+       down_read(&EXT4_I(inode)->i_mmap_sem);
+       result = dax_iomap_fault(vma, vmf, &ext4_iomap_ops);
+       up_read(&EXT4_I(inode)->i_mmap_sem);
+       if (write)
                sb_end_pagefault(sb);
-       } else
-               up_read(&EXT4_I(inode)->i_mmap_sem);
 
        return result;
 }
@@ -292,7 +279,6 @@ static int ext4_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
                                                pmd_t *pmd, unsigned int flags)
 {
        int result;
-       handle_t *handle = NULL;
        struct inode *inode = file_inode(vma->vm_file);
        struct super_block *sb = inode->i_sb;
        bool write = flags & FAULT_FLAG_WRITE;
@@ -300,27 +286,13 @@ 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;
-       else {
-               result = dax_iomap_pmd_fault(vma, addr, pmd, flags,
-                                            &ext4_iomap_ops);
        }
-
-       if (write) {
-               if (!IS_ERR(handle))
-                       ext4_journal_stop(handle);
-               up_read(&EXT4_I(inode)->i_mmap_sem);
+       down_read(&EXT4_I(inode)->i_mmap_sem);
+       result = dax_iomap_pmd_fault(vma, addr, pmd, flags,
+                                    &ext4_iomap_ops);
+       up_read(&EXT4_I(inode)->i_mmap_sem);
+       if (write)
                sb_end_pagefault(sb);
-       } else
-               up_read(&EXT4_I(inode)->i_mmap_sem);
 
        return result;
 }