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ext4: start transaction before calling into DAX

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Jan Kara pointed out that in the case where we are writing to a hole, we
can end up with a lock inversion between the page lock and the journal
lock.  We can avoid this by starting the transaction in ext4 before
calling into DAX.  The journal lock nests inside the superblock
pagefault lock, so we have to duplicate that code from dax_fault, like
XFS does.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matthew Wilcox 2015-09-08 14:59:22 -07:00 committed by Linus Torvalds
parent ed923b5776
commit 01a33b4ace
1 changed files with 52 additions and 3 deletions
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55
fs/ext4/file.c
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@ -207,14 +207,63 @@ static void ext4_end_io_unwritten(struct buffer_head *bh, int uptodate)
static int ext4_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
return dax_fault(vma, vmf, ext4_get_block_dax, ext4_end_io_unwritten);
int result;
handle_t *handle = NULL;
struct super_block *sb = file_inode(vma->vm_file)->i_sb;
bool write = vmf->flags & FAULT_FLAG_WRITE;
if (write) {
sb_start_pagefault(sb);
file_update_time(vma->vm_file);
handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE,
EXT4_DATA_TRANS_BLOCKS(sb));
}
if (IS_ERR(handle))
result = VM_FAULT_SIGBUS;
else
result = __dax_fault(vma, vmf, ext4_get_block_dax,
ext4_end_io_unwritten);
if (write) {
if (!IS_ERR(handle))
ext4_journal_stop(handle);
sb_end_pagefault(sb);
}
return result;
}
static int ext4_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
pmd_t *pmd, unsigned int flags)
{
return dax_pmd_fault(vma, addr, pmd, flags, ext4_get_block_dax,
ext4_end_io_unwritten);
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;
if (write) {
sb_start_pagefault(sb);
file_update_time(vma->vm_file);
handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE,
ext4_chunk_trans_blocks(inode,
PMD_SIZE / PAGE_SIZE));
}
if (IS_ERR(handle))
result = VM_FAULT_SIGBUS;
else
result = __dax_pmd_fault(vma, addr, pmd, flags,
ext4_get_block_dax, ext4_end_io_unwritten);
if (write) {
if (!IS_ERR(handle))
ext4_journal_stop(handle);
sb_end_pagefault(sb);
}
return result;
}
static int ext4_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)