Re: [PATCH 2/9] vfs: export do_splice_direct() to modules

[J. R. Okajima]

Al Viro:
> The scenario, BTW, looks so:
> process A does sb_start_write() (on your upper layer)
> process B tries to freeze said upper layer and blocks, waiting for A to finish
> process C grabs ->i_mutex in your upper layer
> process C does vfs_write(), which blocks, since there's a pending attempt to
> freeze
> process A tries to grab ->i_mutex held by C and blocks

According to latest mm/filemap.c:generic_file_aio_write(),
	sb_start_write(inode->i_sb);
	mutex_lock(&inode->i_mutex);
	ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
	mutex_unlock(&inode->i_mutex);
	:::
	sb_end_write(inode->i_sb);

Process C would block *BEFORE* i_mutex by sb_start_write()? No?
Honestly speaking I didn't pay attention about the freeze feature since
I don't use it. I am making aufs to support it now. But I don't know how
to test it...


J. R. Okajima
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/