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

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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: Jan Kara <jack@suse.cz>
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Ross Zwisler 2016-02-27 14:01:13 -05:00 committed by Theodore Ts'o
parent 74dae42785
commit 1e9d180ba3
2 changed files with 3 additions and 35 deletions
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19
fs/ext2/file.c
View file

@ -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,
};

19
fs/ext4/file.c
View file

@ -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