Commit fb26a1cb authored by Jan Kara's avatar Jan Kara Committed by Linus Torvalds

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: 9f141d6e
Link: http://lkml.kernel.org/r/20170510085419.27601-4-jack@suse.czSigned-off-by: default avatarJan 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent cd656375
......@@ -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;
}
......
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