The patch titled
Subject: ext4: start transaction before calling into DAX
has been added to the -mm tree. Its filename is
ext4-start-transaction-before-calling-into-dax.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ext4-start-transaction-before-calling-into-dax.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ext4-start-transaction-before-calling-into-dax.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
Subject: 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: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/ext4/file.c | 55 ++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 52 insertions(+), 3 deletions(-)
diff -puN fs/ext4/file.c~ext4-start-transaction-before-calling-into-dax fs/ext4/file.c
--- a/fs/ext4/file.c~ext4-start-transaction-before-calling-into-dax
+++ a/fs/ext4/file.c
@@ -207,14 +207,63 @@ static void ext4_end_io_unwritten(struct
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)
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxxxx are
mm-make-gup-handle-pfn-mapping-unless-foll_get-is-requested.patch
mm-make-gup-handle-pfn-mapping-unless-foll_get-is-requested-fix.patch
dax-move-dax-related-functions-to-a-new-header.patch
dax-revert-userfaultfd-change.patch
thp-prepare-for-dax-huge-pages.patch
thp-prepare-for-dax-huge-pages-fix.patch
mm-add-a-pmd_fault-handler.patch
mm-export-various-functions-for-the-benefit-of-dax.patch
mm-add-vmf_insert_pfn_pmd.patch
dax-add-huge-page-fault-support.patch
ext2-huge-page-fault-support.patch
ext4-huge-page-fault-support.patch
xfs-huge-page-fault-support.patch
ext4-use-ext4_get_block_write-for-dax.patch
thp-change-insert_pfns-return-type-to-void.patch
dax-improve-comment-about-truncate-race.patch
ext4-add-ext4_get_block_dax.patch
ext4-start-transaction-before-calling-into-dax.patch
dax-fix-race-between-simultaneous-faults.patch
thp-decrement-refcount-on-huge-zero-page-if-it-is-split.patch
thp-fix-zap_huge_pmd-for-dax.patch
dax-dont-use-set_huge_zero_page.patch
dax-ensure-that-zero-pages-are-removed-from-other-processes.patch
dax-use-linear_page_index.patch
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