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authorJan Kara <jack@suse.cz>2017-05-12 15:46:54 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-05-12 15:57:16 -0700
commitfb26a1cbed8c90025572d48bc9eabe59f7571e88 (patch)
tree900f3fb406c1c78f42d8d036c89de2a8fc452993
parentcd656375f94632d7b5af57bf67b7b5c0270c591c (diff)
downloadlinux-stericsson-fb26a1cbed8c90025572d48bc9eabe59f7571e88.tar.gz
ext4: return to starting transaction in ext4_dax_huge_fault()
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 Link: http://lkml.kernel.org/r/20170510085419.27601-4-jack@suse.cz Signed-off-by: Jan Kara <jack@suse.cz> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/ext4/file.c21
1 files 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;
}