NVDIMM Device and Persistent Memory development
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From: Jan Kara <jack@suse.cz>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Jan Kara <jack@suse.cz>,
	linux-nvdimm@lists.01.org, stable@vger.kernel.org,
	linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
	linux-ext4@vger.kernel.org
Subject: [PATCH 3/4] ext4: Return back to starting transaction in ext4_dax_huge_fault()
Date: Wed, 10 May 2017 10:54:18 +0200
Message-ID: <20170510085419.27601-4-jack@suse.cz> (raw)
In-Reply-To: <20170510085419.27601-1-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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  parent reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
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 1/4] dax: prevent invalidation of mapped DAX entries Jan Kara
2017-05-10  8:54 ` [PATCH 2/4] mm: Fix data corruption due to stale mmap reads Jan Kara
2017-05-10  8:54 ` Jan Kara [this message]
2017-05-10 17:27 ` [PATCH 0/4 v4] mm,dax: Fix data corruption due to mmap inconsistency Ross Zwisler
  -- strict thread matches above, loose matches on Subject: below --
2017-05-10  8:54 [PATCH 4/4] dax: Fix data corruption when fault races with write Jan Kara
2017-05-10 17:27 ` [PATCH 5/4] dax: Fix PMD " Ross Zwisler
2017-05-11  8:39   ` Jan Kara
2017-05-09 12:18 [PATCH 0/4 v3] mm,dax: Fix data corruption due to mmap inconsistency Jan Kara
2017-05-09 12:18 ` [PATCH 3/4] ext4: Return back to starting transaction in ext4_dax_huge_fault() Jan Kara
2017-05-05  7:24 [PATCH 0/4 v2] mm,dax: Fix data corruption due to mmap inconsistency Jan Kara
2017-05-05  7:24 ` [PATCH 3/4] ext4: Return back to starting transaction in ext4_dax_huge_fault() Jan Kara

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