From 1ba4997eae536e0cb4feb0af2f145bf7ba56eb17 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Tue, 8 Sep 2015 14:59:22 -0700 Subject: [PATCH] ext4: start transaction before calling into DAX Orabug: 22913653 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 Cc: Jan Kara Cc: Theodore Ts'o Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds (cherry picked from commit 01a33b4ace68bc35679a347f21d5ed6e222e30dc) Signed-off-by: Dan Duval --- fs/ext4/file.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 52 insertions(+), 3 deletions(-) diff --git a/fs/ext4/file.c b/fs/ext4/file.c index a9f334f590753..b30019c7f2cd1 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -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) -- 2.50.1