Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1200271

[PATCH 05/11] ext4: Start transaction before calling into DAX

Show all headers | View raw

From: Matthew Wilcox <willy@linux.intel.com>

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>
---
 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 d5219e4..113837e 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)
-- 
2.1.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

[PATCH 00/11] DAX fixes for 4.3 Matthew Wilcox <matthew.r.wilcox@intel.com> - 2015-08-04 22:00 +0200
  [PATCH 10/11] dax: Ensure that zero pages are removed from other processes Matthew Wilcox <matthew.r.wilcox@intel.com> - 2015-08-04 22:00 +0200
  [PATCH 09/11] dax: Don't use set_huge_zero_page() Matthew Wilcox <matthew.r.wilcox@intel.com> - 2015-08-04 22:00 +0200
  [PATCH 07/11] thp: Decrement refcount on huge zero page if it is split Matthew Wilcox <matthew.r.wilcox@intel.com> - 2015-08-04 22:00 +0200
  [PATCH 08/11] thp: Fix zap_huge_pmd() for DAX Matthew Wilcox <matthew.r.wilcox@intel.com> - 2015-08-04 22:00 +0200
  [PATCH 01/11] ext4: Use ext4_get_block_write() for DAX Matthew Wilcox <matthew.r.wilcox@intel.com> - 2015-08-04 22:10 +0200
  [PATCH 06/11] dax: Fix race between simultaneous faults Matthew Wilcox <matthew.r.wilcox@intel.com> - 2015-08-04 22:10 +0200
    Re: [PATCH 06/11] dax: Fix race between simultaneous faults "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-08-05 13:50 +0200
  [PATCH 11/11] dax: Use linear_page_index() Matthew Wilcox <matthew.r.wilcox@intel.com> - 2015-08-04 22:10 +0200
  [PATCH 04/11] ext4: Add ext4_get_block_dax() Matthew Wilcox <matthew.r.wilcox@intel.com> - 2015-08-04 22:10 +0200
    Re: [PATCH 04/11] ext4: Add ext4_get_block_dax() Dave Chinner <david@fromorbit.com> - 2015-08-05 04:10 +0200
      Re: [PATCH 04/11] ext4: Add ext4_get_block_dax() Matthew Wilcox <willy@linux.intel.com> - 2015-08-05 17:20 +0200
  [PATCH 05/11] ext4: Start transaction before calling into DAX Matthew Wilcox <matthew.r.wilcox@intel.com> - 2015-08-04 22:10 +0200

csiph-web