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Use f_lock to protect f_flags

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Traditionally, changes to struct file->f_flags have been done under BKL
protection, or with no protection at all.  This patch causes all f_flags
changes after file open/creation time to be done under protection of
f_lock.  This allows the removal of some BKL usage and fixes a number of
longstanding (if microscopic) races.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Jonathan Corbet
2009-02-06 15:25:24 -07:00
parent 6849991490
commit db1dd4d376
13 changed files with 33 additions and 9 deletions
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7
fs/ioctl.c
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@@ -404,10 +404,12 @@ static int ioctl_fionbio(struct file *filp, int __user *argp)
if (O_NONBLOCK != O_NDELAY)
flag |= O_NDELAY;
#endif
spin_lock(&filp->f_lock);
if (on)
filp->f_flags |= flag;
else
filp->f_flags &= ~flag;
spin_unlock(&filp->f_lock);
return error;
}
@@ -432,10 +434,12 @@ static int ioctl_fioasync(unsigned int fd, struct file *filp,
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;
}
@@ -499,10 +503,7 @@ int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
break;
case FIONBIO:
/* BKL needed to avoid races tweaking f_flags */
lock_kernel();
error = ioctl_fionbio(filp, argp);
unlock_kernel();
break;
case FIOASYNC: