Re: [PATCH 3/9] VFS: Introduce a mount context

From: David Howells
Date: Wed May 03 2017 - 14:37:53 EST

Joe Perches <joe@xxxxxxxxxxx> wrote:

> krealloc would probably be more efficient and possible
> readable as likely there's already padding in the original
> allocation.

The problem is if krealloc() fails: you've lost all those pointers to things
you then need to free.

> Are there no locking constraints?

Generally, no, not until you do the ->mount() op. Also remounting needs a
lock, but that's already done with the sb->s_umount lock.

However, that said, if you do:

fd = fsopen("foofs");
write(fd, "o foo=bar", ...);
fsmount(fd, "/foo");

then the fsmount() and write() calls have to lock against other fsmount() and
write() calls. I use the inode lock for this. [Note that it probably should
be interruptible rather than just killable, but there's no primitive for that
as yet].