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ext4: return to starting transaction in ext4_dax_huge_fault()

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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: 9f141d6ef6
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Jan Kara <[email protected]>
Cc: Ross Zwisler <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Jan Kara 2017-05-12 15:46:54 -07:00 • committed by Linus Torvalds
commit fb26a1cbed
1 changed files with 17 additions and 4 deletions
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21
fs/ext4/file.c
View file

@ -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;
}