diff options
| author | Jonathan Corbet <corbet@lwn.net> | 2009-02-01 14:26:59 -0700 |
|---|---|---|
| committer | Jonathan Corbet <corbet@lwn.net> | 2009-03-16 08:32:27 -0600 |
| commit | 76398425bb06b07cc3a3b1ce169c67dc9d6874ed (patch) | |
| tree | e6e1800edda88b5592617a950daacf2199587a33 /fs/ioctl.c | |
| parent | db1dd4d376134eba0e08af523b61cc566a4ea1cd (diff) | |
Move FASYNC bit handling to f_op->fasync()
Removing the BKL from FASYNC handling ran into the challenge of keeping the
setting of the FASYNC bit in filp->f_flags atomic with regard to calls to
the underlying fasync() function. Andi Kleen suggested moving the handling
of that bit into fasync(); this patch does exactly that. As a result, we
have a couple of internal API changes: fasync() must now manage the FASYNC
bit, and it will be called without the BKL held.
As it happens, every fasync() implementation in the kernel with one
exception calls fasync_helper(). So, if we make fasync_helper() set the
FASYNC bit, we can avoid making any changes to the other fasync()
functions - as long as those functions, themselves, have proper locking.
Most fasync() implementations do nothing but call fasync_helper() - which
has its own lock - so they are easily verified as correct. The BKL had
already been pushed down into the rest.
The networking code has its own version of fasync_helper(), so that code
has been augmented with explicit FASYNC bit handling.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: David Miller <davem@davemloft.net>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'fs/ioctl.c')
| -rw-r--r-- | fs/ioctl.c | 13 |
1 files changed, 1 insertions, 12 deletions
diff --git a/fs/ioctl.c b/fs/ioctl.c index 421aab465dab..e8e89edba576 100644 --- a/fs/ioctl.c +++ b/fs/ioctl.c @@ -427,19 +427,11 @@ static int ioctl_fioasync(unsigned int fd, struct file *filp, /* Did FASYNC state change ? */ if ((flag ^ filp->f_flags) & FASYNC) { if (filp->f_op && filp->f_op->fasync) + /* fasync() adjusts filp->f_flags */ error = filp->f_op->fasync(fd, filp, on); else error = -ENOTTY; } - if (error) - return error; - - spin_lock(&filp->f_lock); - if (on) - filp->f_flags |= FASYNC; - else - filp->f_flags &= ~FASYNC; - spin_unlock(&filp->f_lock); return error; } @@ -507,10 +499,7 @@ int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd, break; case FIOASYNC: - /* BKL needed to avoid races tweaking f_flags */ - lock_kernel(); error = ioctl_fioasync(fd, filp, argp); - unlock_kernel(); break; case FIOQSIZE: |