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Commit 1e9d180b authored by Ross Zwisler's avatar Ross Zwisler Committed by Theodore Ts'o
Browse files

ext2, ext4: fix issue with missing journal entry in ext4_dax_mkwrite() 



As it is currently written ext4_dax_mkwrite() assumes that the call into
__dax_mkwrite() will not have to do a block allocation so it doesn't create
a journal entry.  For a read that creates a zero page to cover a hole
followed by a write that actually allocates storage this is incorrect.  The
ext4_dax_mkwrite() -> __dax_mkwrite() -> __dax_fault() path calls
get_blocks() to allocate storage.

Fix this by having the ->page_mkwrite fault handler call ext4_dax_fault()
as this function already has all the logic needed to allocate a journal
entry and call __dax_fault().

Also update the ext2 fault handlers in this same way to remove duplicate
code and keep the logic between ext2 and ext4 the same.

Reviewed-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 74dae427

fs/ext2/file.c

+1 −18
Original line number Diff line number Diff line
@@ -80,23 +80,6 @@ static int ext2_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr, 
	return ret;

}



static int ext2_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)

{

	struct inode *inode = file_inode(vma->vm_file);

	struct ext2_inode_info *ei = EXT2_I(inode);

	int ret;



	sb_start_pagefault(inode->i_sb);

	file_update_time(vma->vm_file);

	down_read(&ei->dax_sem);



	ret = __dax_mkwrite(vma, vmf, ext2_get_block, NULL);



	up_read(&ei->dax_sem);

	sb_end_pagefault(inode->i_sb);

	return ret;

}



static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,

		struct vm_fault *vmf)

{
@@ -124,7 +107,7 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma, 
static const struct vm_operations_struct ext2_dax_vm_ops = {

	.fault		= ext2_dax_fault,

	.pmd_fault	= ext2_dax_pmd_fault,

	.page_mkwrite	= ext2_dax_mkwrite,

	.page_mkwrite	= ext2_dax_fault,

	.pfn_mkwrite	= ext2_dax_pfn_mkwrite,

};

fs/ext4/file.c

+2 −17
Original line number Diff line number Diff line
@@ -262,23 +262,8 @@ static int ext4_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr, 
	return result;

}



static int ext4_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)

{

	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_dax_mmap_get_block, NULL);

	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()

 * Handle write fault for VM_MIXEDMAP mappings. Similarly to ext4_dax_fault()

 * 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
@@ -311,7 +296,7 @@ static int ext4_dax_pfn_mkwrite(struct vm_area_struct *vma, 
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,

	.page_mkwrite	= ext4_dax_fault,

	.pfn_mkwrite	= ext4_dax_pfn_mkwrite,

};

#else