From: Jan Kara <jack@suse.cz>
To: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Jan Kara <jack@suse.cz>,
linux-nvdimm@lists.01.org, stable@vger.kernel.org,
linux-fsdevel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
linux-ext4@vger.kernel.org
Subject: [PATCH 3/4] ext4: Return back to starting transaction in ext4_dax_huge_fault()
Date: Fri, 5 May 2017 09:24:59 +0200 [thread overview]
Message-ID: <20170505072500.25692-4-jack@suse.cz> (raw)
In-Reply-To: <20170505072500.25692-1-jack@suse.cz>
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: 9f141d6ef6258a3a37a045842d9ba7e68f368956
CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
---
fs/ext4/file.c | 21 +++++++++++++++++----
1 file changed, 17 insertions(+), 4 deletions(-)
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index cefa9835f275..831fd6beebf0 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -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);
}
- down_read(&EXT4_I(inode)->i_mmap_sem);
- result = dax_iomap_fault(vmf, pe_size, &ext4_iomap_ops);
- up_read(&EXT4_I(inode)->i_mmap_sem);
- if (write)
+ 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);
sb_end_pagefault(sb);
+ } else {
+ up_read(&EXT4_I(inode)->i_mmap_sem);
+ }
return result;
}
--
2.12.0
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next prev parent reply other threads:[~2017-05-05 7:25 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-05 7:24 [PATCH 0/4 v2] mm,dax: Fix data corruption due to mmap inconsistency Jan Kara
2017-05-05 7:24 ` [PATCH 1/4] dax: prevent invalidation of mapped DAX entries Jan Kara
2017-05-05 7:24 ` [PATCH 2/4] mm: Fix data corruption due to stale mmap reads Jan Kara
2017-05-05 7:24 ` Jan Kara [this message]
2017-05-05 7:25 ` [PATCH 4/4] dax: Fix data corruption when fault races with write Jan Kara
2017-05-08 17:25 ` Ross Zwisler
2017-05-09 12:14 ` Jan Kara
2017-05-08 17:27 ` [PATCH 0/4 v2] mm,dax: Fix data corruption due to mmap inconsistency Ross Zwisler
2017-05-09 12:18 [PATCH 0/4 v3] " Jan Kara
2017-05-09 12:18 ` [PATCH 3/4] ext4: Return back to starting transaction in ext4_dax_huge_fault() Jan Kara
2017-05-10 8:54 [PATCH 0/4 v4] mm,dax: Fix data corruption due to mmap inconsistency Jan Kara
2017-05-10 8:54 ` [PATCH 3/4] ext4: Return back to starting transaction in ext4_dax_huge_fault() Jan Kara
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