On Fri, 14 Feb 2014 13:31:03 +0400
Pavel Shilovsky <piastry@xxxxxxxxxxx> wrote:
> and use generic_file_aio_write rather than __generic_file_aio_write
> in cifs_writev.
>
> Signed-off-by: Pavel Shilovsky <piastry@xxxxxxxxxxx>
Al reported this, so you may want to add:
Reported-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
...and cc him.
> ---
> fs/cifs/file.c | 24 ++++++------------------
> 1 file changed, 6 insertions(+), 18 deletions(-)
>
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index a7eda8e..d34dc3b 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -2539,31 +2539,19 @@ cifs_writev(struct kiocb *iocb, const struct iovec *iov,
> struct cifsInodeInfo *cinode = CIFS_I(inode);
> struct TCP_Server_Info *server = tlink_tcon(cfile->tlink)->ses->server;
> ssize_t rc = -EACCES;
> + loff_t lock_pos = pos;
>
> - BUG_ON(iocb->ki_pos != pos);
> -
> + if (file->f_flags & O_APPEND)
> + lock_pos = i_size_read(inode);
Hmm...
I'll note that when we do the i_size_read in generic_write_checks, the
i_mutex is held. It's not held here though -- is that a potential race?
Could the i_size change after you check for locks but before you do the
I/O?
vfs.txt says:
"Adding and removing pages to/from an address_space is protected by the
inode's i_mutex."
That said, I don't have a great feel for how the locking rules work in
this regard...
> /*
> * We need to hold the sem to be sure nobody modifies lock list
> * with a brlock that prevents writing.
> */
> down_read(&cinode->lock_sem);
> - if (!cifs_find_lock_conflict(cfile, pos, iov_length(iov, nr_segs),
> + if (!cifs_find_lock_conflict(cfile, lock_pos, iov_length(iov, nr_segs),
> server->vals->exclusive_lock_type, NULL,
> - CIFS_WRITE_OP)) {
> - mutex_lock(&inode->i_mutex);
> - rc = __generic_file_aio_write(iocb, iov, nr_segs,
> - &iocb->ki_pos);
> - mutex_unlock(&inode->i_mutex);
> - }
> -
> - if (rc > 0) {
> - ssize_t err;
> -
> - err = generic_write_sync(file, iocb->ki_pos - rc, rc);
> - if (err < 0)
> - rc = err;
> - }
> -
> + CIFS_WRITE_OP))
> + rc = generic_file_aio_write(iocb, iov, nr_segs, pos);
> up_read(&cinode->lock_sem);
> return rc;
> }
--
Jeff Layton <jlayton@xxxxxxxxxx>
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