The patch titled
fasync: move bit handling to f_op->fasync()
has been removed from the -mm tree. Its filename was
fasync-move-bit-handling-to-f_op-fasync.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: fasync: move bit handling to f_op->fasync()
From: Jonathan Corbet <corbet@xxxxxxx>
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.
Signed-off-by: Jonathan Corbet <corbet@xxxxxxx>
Acked-by: Matt Mackall <mpm@xxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/fcntl.c | 29 ++++++++++++++++-------------
fs/ioctl.c | 13 +------------
net/socket.c | 8 ++++++++
3 files changed, 25 insertions(+), 25 deletions(-)
diff -puN fs/fcntl.c~fasync-move-bit-handling-to-f_op-fasync fs/fcntl.c
--- a/fs/fcntl.c~fasync-move-bit-handling-to-f_op-fasync
+++ a/fs/fcntl.c
@@ -141,7 +141,7 @@ SYSCALL_DEFINE1(dup, unsigned int, filde
return ret;
}
-#define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | FASYNC | O_DIRECT | O_NOATIME)
+#define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT | O_NOATIME)
static int setfl(int fd, struct file * filp, unsigned long arg)
{
@@ -177,23 +177,19 @@ static int setfl(int fd, struct file * f
return error;
/*
- * We still need a lock here for now to keep multiple FASYNC calls
- * from racing with each other.
+ * ->fasync() is responsible for setting the FASYNC bit.
*/
- lock_kernel();
- if ((arg ^ filp->f_flags) & FASYNC) {
- if (filp->f_op && filp->f_op->fasync) {
- error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
- if (error < 0)
- goto out;
- }
+ if (((arg ^ filp->f_flags) & FASYNC) && filp->f_op &&
+ filp->f_op->fasync) {
+ error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
+ if (error < 0)
+ goto out;
}
-
spin_lock(&filp->f_lock);
filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
spin_unlock(&filp->f_lock);
+
out:
- unlock_kernel();
return error;
}
@@ -518,7 +514,7 @@ static DEFINE_RWLOCK(fasync_lock);
static struct kmem_cache *fasync_cache __read_mostly;
/*
- * fasync_helper() is used by some character device drivers (mainly mice)
+ * fasync_helper() is used by almost all character device drivers
* to set up the fasync queue. It returns negative on error, 0 if it did
* no changes and positive if it added/deleted the entry.
*/
@@ -557,6 +553,13 @@ int fasync_helper(int fd, struct file *
result = 1;
}
out:
+ /* Fix up FASYNC bit while still holding fasync_lock */
+ spin_lock(&filp->f_lock);
+ if (on)
+ filp->f_flags |= FASYNC;
+ else
+ filp->f_flags &= ~FASYNC;
+ spin_unlock(&filp->f_lock);
write_unlock_irq(&fasync_lock);
return result;
}
diff -puN fs/ioctl.c~fasync-move-bit-handling-to-f_op-fasync fs/ioctl.c
--- a/fs/ioctl.c~fasync-move-bit-handling-to-f_op-fasync
+++ a/fs/ioctl.c
@@ -427,19 +427,11 @@ static int ioctl_fioasync(unsigned int f
/* 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, unsi
break;
case FIOASYNC:
- /* BKL needed to avoid races tweaking f_flags */
- lock_kernel();
error = ioctl_fioasync(fd, filp, argp);
- unlock_kernel();
break;
case FIOQSIZE:
diff -puN net/socket.c~fasync-move-bit-handling-to-f_op-fasync net/socket.c
--- a/net/socket.c~fasync-move-bit-handling-to-f_op-fasync
+++ a/net/socket.c
@@ -1030,6 +1030,14 @@ static int sock_fasync(int fd, struct fi
lock_sock(sk);
+ /* Maintaining the FASYNC bit is our job now */
+ spin_lock(&filp->f_lock);
+ if (on)
+ filp->f_flags |= FASYNC;
+ else
+ filp->f_flags &= ~FASYNC;
+ spin_unlock(&filp->f_lock);
+
prev = &(sock->fasync_list);
for (fa = *prev; fa != NULL; prev = &fa->fa_next, fa = *prev)
_
Patches currently in -mm which might be from corbet@xxxxxxx are
linux-next.patch
pipe_rdwr_fasync-fix-the-error-handling-to-prevent-the-leak-crash.patch
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