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ext4: fix DAX write locking 

Unlike O_DIRECT DAX is not an optional opt-in feature selected by the
application, so we'll have to provide the traditional synchronіzation
of overlapping writes as we do for buffered writes.

This was broken historically for DAX, but got fixed for ext2 and XFS
as part of the iomap conversion.  Fix up ext4 as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Christoph Hellwig 2017-02-08 14:39:27 -05:00 committed by Theodore Ts'o
parent 783d948544
commit ff5462e39c
1 changed files with 1 additions and 9 deletions
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10
fs/ext4/file.c
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@ -178,7 +178,6 @@ ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
struct inode *inode = file_inode(iocb->ki_filp);
ssize_t ret;
bool overwrite = false;
inode_lock(inode);
ret = ext4_write_checks(iocb, from);
@ -191,16 +190,9 @@ ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
if (ret)
goto out;
if (ext4_overwrite_io(inode, iocb->ki_pos, iov_iter_count(from))) {
overwrite = true;
downgrade_write(&inode->i_rwsem);
}
ret = dax_iomap_rw(iocb, from, &ext4_iomap_ops);
out:
if (!overwrite)
inode_unlock(inode);
else
inode_unlock_shared(inode);
inode_unlock(inode);
if (ret > 0)
ret = generic_write_sync(iocb, ret);
return ret;