ext4: return to starting transaction in ext4_dax_huge_fault() (fb26a1cb) · Commits · 戴 / test

DAX will return to locking exceptional entry before mapping blocks for a page fault to fix possible races with concurrent writes. To avoid lock inversion between exceptional entry lock and transaction start, start the transaction already in ext4_dax_huge_fault(). Fixes: Link: http://lkml.kernel.org/r/20170510085419.27601-4-jack@suse.cz Signed-off-by:

Jan Kara <jack@suse.cz> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: <stable@vger.kernel.org> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

fs/ext4/file.c

+17 −4

Original line number	Diff line number	Diff line
		@@ -257,6 +257,7 @@ static int ext4_dax_huge_fault(struct vm_fault *vmf,
		enum page_entry_size pe_size)
		{
		int result;
		handle_t *handle = NULL;
		struct inode *inode = file_inode(vmf->vma->vm_file);
		struct super_block *sb = inode->i_sb;
		bool write = vmf->flags & FAULT_FLAG_WRITE;
		@@ -264,12 +265,24 @@ static int ext4_dax_huge_fault(struct vm_fault *vmf,
		if (write) {
		sb_start_pagefault(sb);
		file_update_time(vmf->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 = dax_iomap_fault(vmf, pe_size, &ext4_iomap_ops);
		else
		result = VM_FAULT_SIGBUS;
		if (write) {
		if (!IS_ERR(handle))
		ext4_journal_stop(handle);
		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;
		}

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