From d7065da038227a4d09a244e6014e0186a6bd21d0 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 26 May 2010 15:13:55 -0400 Subject: get rid of the magic around f_count in aio __aio_put_req() plays sick games with file refcount. What it wants is fput() from atomic context; it's almost always done with f_count > 1, so they only have to deal with delayed work in rare cases when their reference happens to be the last one. Current code decrements f_count and if it hasn't hit 0, everything is fine. Otherwise it keeps a pointer to struct file (with zero f_count!) around and has delayed work do __fput() on it. Better way to do it: use atomic_long_add_unless( , -1, 1) instead of !atomic_long_dec_and_test(). IOW, decrement it only if it's not the last reference, leave refcount alone if it was. And use normal fput() in delayed work. I've made that atomic_long_add_unless call a new helper - fput_atomic(). Drops a reference to file if it's safe to do in atomic (i.e. if that's not the last one), tells if it had been able to do that. aio.c converted to it, __fput() use is gone. req->ki_file *always* contributes to refcount now. And __fput() became static. Signed-off-by: Al Viro --- fs/aio.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'fs/aio.c') diff --git a/fs/aio.c b/fs/aio.c index 48fdeeb..1ccf25c 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -527,7 +527,7 @@ static void aio_fput_routine(struct work_struct *data) /* Complete the fput(s) */ if (req->ki_filp != NULL) - __fput(req->ki_filp); + fput(req->ki_filp); /* Link the iocb into the context's free list */ spin_lock_irq(&ctx->ctx_lock); @@ -560,11 +560,11 @@ static int __aio_put_req(struct kioctx *ctx, struct kiocb *req) /* * Try to optimize the aio and eventfd file* puts, by avoiding to - * schedule work in case it is not __fput() time. In normal cases, + * schedule work in case it is not final fput() time. In normal cases, * we would not be holding the last reference to the file*, so * this function will be executed w/out any aio kthread wakeup. */ - if (unlikely(atomic_long_dec_and_test(&req->ki_filp->f_count))) { + if (unlikely(!fput_atomic(req->ki_filp))) { get_ioctx(ctx); spin_lock(&fput_lock); list_add(&req->ki_list, &fput_head); -- cgit v1.1