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Commit 01a33b4a authored by Matthew Wilcox's avatar Matthew Wilcox Committed by Linus Torvalds
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ext4: start transaction before calling into DAX 



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: default avatarMatthew Wilcox <willy@linux.intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ed923b57

fs/ext4/file.c

+52 −3
Original line number Diff line number Diff line
@@ -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)