llseek: automatically add .llseek fop

All file_operations should get a .llseek operation so we can make
nonseekable_open the default for future file operations without a
.llseek pointer.

The three cases that we can automatically detect are no_llseek, seq_lseek
and default_llseek. For cases where we can we can automatically prove that
the file offset is always ignored, we use noop_llseek, which maintains
the current behavior of not returning an error from a seek.

New drivers should normally not use noop_llseek but instead use no_llseek
and call nonseekable_open at open time.  Existing drivers can be converted
to do the same when the maintainer knows for certain that no user code
relies on calling seek on the device file.

The generated code is often incorrectly indented and right now contains
comments that clarify for each added line why a specific variant was
chosen. In the version that gets submitted upstream, the comments will
be gone and I will manually fix the indentation, because there does not
seem to be a way to do that using coccinelle.

Some amount of new code is currently sitting in linux-next that should get
the same modifications, which I will do at the end of the merge window.

Many thanks to Julia Lawall for helping me learn to write a semantic
patch that does all this.

===== begin semantic patch =====
// This adds an llseek= method to all file operations,
// as a preparation for making no_llseek the default.
//
// The rules are
// - use no_llseek explicitly if we do nonseekable_open
// - use seq_lseek for sequential files
// - use default_llseek if we know we access f_pos
// - use noop_llseek if we know we don't access f_pos,
//   but we still want to allow users to call lseek
//
@ open1 exists @
identifier nested_open;
@@
nested_open(...)
{
<+...
nonseekable_open(...)
...+>
}

@ open exists@
identifier open_f;
identifier i, f;
identifier open1.nested_open;
@@
int open_f(struct inode *i, struct file *f)
{
<+...
(
nonseekable_open(...)
|
nested_open(...)
)
...+>
}

@ read disable optional_qualifier exists @
identifier read_f;
identifier f, p, s, off;
type ssize_t, size_t, loff_t;
expression E;
identifier func;
@@
ssize_t read_f(struct file *f, char *p, size_t s, loff_t *off)
{
<+...
(
   *off = E
|
   *off += E
|
   func(..., off, ...)
|
   E = *off
)
...+>
}

@ read_no_fpos disable optional_qualifier exists @
identifier read_f;
identifier f, p, s, off;
type ssize_t, size_t, loff_t;
@@
ssize_t read_f(struct file *f, char *p, size_t s, loff_t *off)
{
... when != off
}

@ write @
identifier write_f;
identifier f, p, s, off;
type ssize_t, size_t, loff_t;
expression E;
identifier func;
@@
ssize_t write_f(struct file *f, const char *p, size_t s, loff_t *off)
{
<+...
(
  *off = E
|
  *off += E
|
  func(..., off, ...)
|
  E = *off
)
...+>
}

@ write_no_fpos @
identifier write_f;
identifier f, p, s, off;
type ssize_t, size_t, loff_t;
@@
ssize_t write_f(struct file *f, const char *p, size_t s, loff_t *off)
{
... when != off
}

@ fops0 @
identifier fops;
@@
struct file_operations fops = {
 ...
};

@ has_llseek depends on fops0 @
identifier fops0.fops;
identifier llseek_f;
@@
struct file_operations fops = {
...
 .llseek = llseek_f,
...
};

@ has_read depends on fops0 @
identifier fops0.fops;
identifier read_f;
@@
struct file_operations fops = {
...
 .read = read_f,
...
};

@ has_write depends on fops0 @
identifier fops0.fops;
identifier write_f;
@@
struct file_operations fops = {
...
 .write = write_f,
...
};

@ has_open depends on fops0 @
identifier fops0.fops;
identifier open_f;
@@
struct file_operations fops = {
...
 .open = open_f,
...
};

// use no_llseek if we call nonseekable_open
////////////////////////////////////////////
@ nonseekable1 depends on !has_llseek && has_open @
identifier fops0.fops;
identifier nso ~= "nonseekable_open";
@@
struct file_operations fops = {
...  .open = nso, ...
+.llseek = no_llseek, /* nonseekable */
};

@ nonseekable2 depends on !has_llseek @
identifier fops0.fops;
identifier open.open_f;
@@
struct file_operations fops = {
...  .open = open_f, ...
+.llseek = no_llseek, /* open uses nonseekable */
};

// use seq_lseek for sequential files
/////////////////////////////////////
@ seq depends on !has_llseek @
identifier fops0.fops;
identifier sr ~= "seq_read";
@@
struct file_operations fops = {
...  .read = sr, ...
+.llseek = seq_lseek, /* we have seq_read */
};

// use default_llseek if there is a readdir
///////////////////////////////////////////
@ fops1 depends on !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier readdir_e;
@@
// any other fop is used that changes pos
struct file_operations fops = {
... .readdir = readdir_e, ...
+.llseek = default_llseek, /* readdir is present */
};

// use default_llseek if at least one of read/write touches f_pos
/////////////////////////////////////////////////////////////////
@ fops2 depends on !fops1 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier read.read_f;
@@
// read fops use offset
struct file_operations fops = {
... .read = read_f, ...
+.llseek = default_llseek, /* read accesses f_pos */
};

@ fops3 depends on !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier write.write_f;
@@
// write fops use offset
struct file_operations fops = {
... .write = write_f, ...
+	.llseek = default_llseek, /* write accesses f_pos */
};

// Use noop_llseek if neither read nor write accesses f_pos
///////////////////////////////////////////////////////////

@ fops4 depends on !fops1 && !fops2 && !fops3 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier read_no_fpos.read_f;
identifier write_no_fpos.write_f;
@@
// write fops use offset
struct file_operations fops = {
...
 .write = write_f,
 .read = read_f,
...
+.llseek = noop_llseek, /* read and write both use no f_pos */
};

@ depends on has_write && !has_read && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier write_no_fpos.write_f;
@@
struct file_operations fops = {
... .write = write_f, ...
+.llseek = noop_llseek, /* write uses no f_pos */
};

@ depends on has_read && !has_write && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier read_no_fpos.read_f;
@@
struct file_operations fops = {
... .read = read_f, ...
+.llseek = noop_llseek, /* read uses no f_pos */
};

@ depends on !has_read && !has_write && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
@@
struct file_operations fops = {
...
+.llseek = noop_llseek, /* no read or write fn */
};
===== End semantic patch =====

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Julia Lawall <julia@diku.dk>
Cc: Christoph Hellwig <hch@infradead.org>

24 files changed, 30 insertions, 1 deletions

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index 1409131..fecb89e 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -1922,6 +1922,7 @@ const struct file_operations comedi_fops = {
 	.mmap = comedi_mmap,
 	.poll = comedi_poll,
 	.fasync = comedi_fasync,
+	.llseek = noop_llseek,
 };
 
 struct class *comedi_class;
diff --git a/drivers/staging/crystalhd/crystalhd_lnx.c b/drivers/staging/crystalhd/crystalhd_lnx.c
index fbb80f0..af25899 100644
--- a/drivers/staging/crystalhd/crystalhd_lnx.c
+++ b/drivers/staging/crystalhd/crystalhd_lnx.c
@@ -351,6 +351,7 @@ static const struct file_operations chd_dec_fops = {
 	.unlocked_ioctl = chd_dec_ioctl,
 	.open    = chd_dec_open,
 	.release = chd_dec_close,
+	.llseek = noop_llseek,
 };
 
 static int __devinit chd_dec_init_chdev(struct crystalhd_adp *adp)
diff --git a/drivers/staging/dream/camera/msm_camera.c b/drivers/staging/dream/camera/msm_camera.c
index 81bd71f..de4ab61 100644
--- a/drivers/staging/dream/camera/msm_camera.c
+++ b/drivers/staging/dream/camera/msm_camera.c
@@ -1941,6 +1941,7 @@ static const struct file_operations msm_fops_config = {
 	.open = msm_open,
 	.unlocked_ioctl = msm_ioctl_config,
 	.release = msm_release_config,
+	.llseek = no_llseek,
 };
 
 static const struct file_operations msm_fops_control = {
@@ -1948,6 +1949,7 @@ static const struct file_operations msm_fops_control = {
 	.open = msm_open_control,
 	.unlocked_ioctl = msm_ioctl_control,
 	.release = msm_release_control,
+	.llseek = no_llseek,
 };
 
 static const struct file_operations msm_fops_frame = {
@@ -1956,6 +1958,7 @@ static const struct file_operations msm_fops_frame = {
 	.unlocked_ioctl = msm_ioctl_frame,
 	.release = msm_release_frame,
 	.poll = msm_poll_frame,
+	.llseek = no_llseek,
 };
 
 static int msm_setup_cdev(struct msm_device *msm,
diff --git a/drivers/staging/dream/pmem.c b/drivers/staging/dream/pmem.c
index 7d6bbad..3640d1f 100644
--- a/drivers/staging/dream/pmem.c
+++ b/drivers/staging/dream/pmem.c
@@ -180,6 +180,7 @@ const struct file_operations pmem_fops = {
 	.mmap = pmem_mmap,
 	.open = pmem_open,
 	.unlocked_ioctl = pmem_ioctl,
+	.llseek = noop_llseek,
 };
 
 static int get_id(struct file *file)
@@ -1204,6 +1205,7 @@ static ssize_t debug_read(struct file *file, char __user *buf, size_t count,
 static struct file_operations debug_fops = {
 	.read = debug_read,
 	.open = debug_open,
+	.llseek = default_llseek,
 };
 #endif
 
diff --git a/drivers/staging/dream/qdsp5/adsp_driver.c b/drivers/staging/dream/qdsp5/adsp_driver.c
index 8197765..28a6f8d 100644
--- a/drivers/staging/dream/qdsp5/adsp_driver.c
+++ b/drivers/staging/dream/qdsp5/adsp_driver.c
@@ -582,6 +582,7 @@ static struct file_operations adsp_fops = {
 	.open = adsp_open,
 	.unlocked_ioctl = adsp_ioctl,
 	.release = adsp_release,
+	.llseek = no_llseek,
 };
 
 static void adsp_create(struct adsp_device *adev, const char *name,
diff --git a/drivers/staging/dream/qdsp5/audio_aac.c b/drivers/staging/dream/qdsp5/audio_aac.c
index a373f35..45f4c78 100644
--- a/drivers/staging/dream/qdsp5/audio_aac.c
+++ b/drivers/staging/dream/qdsp5/audio_aac.c
@@ -1030,6 +1030,7 @@ static struct file_operations audio_aac_fops = {
 	.read = audio_read,
 	.write = audio_write,
 	.unlocked_ioctl = audio_ioctl,
+	.llseek = noop_llseek,
 };
 
 struct miscdevice audio_aac_misc = {
diff --git a/drivers/staging/dream/qdsp5/audio_amrnb.c b/drivers/staging/dream/qdsp5/audio_amrnb.c
index 07b79d5..402bbc1 100644
--- a/drivers/staging/dream/qdsp5/audio_amrnb.c
+++ b/drivers/staging/dream/qdsp5/audio_amrnb.c
@@ -841,6 +841,7 @@ static struct file_operations audio_amrnb_fops = {
 	.read = audamrnb_read,
 	.write = audamrnb_write,
 	.unlocked_ioctl = audamrnb_ioctl,
+	.llseek = noop_llseek,
 };
 
 struct miscdevice audio_amrnb_misc = {
diff --git a/drivers/staging/dream/qdsp5/audio_evrc.c b/drivers/staging/dream/qdsp5/audio_evrc.c
index ad989ee..24a8926 100644
--- a/drivers/staging/dream/qdsp5/audio_evrc.c
+++ b/drivers/staging/dream/qdsp5/audio_evrc.c
@@ -813,6 +813,7 @@ static struct file_operations audio_evrc_fops = {
 	.read = audevrc_read,
 	.write = audevrc_write,
 	.unlocked_ioctl = audevrc_ioctl,
+	.llseek = noop_llseek,
 };
 
 struct miscdevice audio_evrc_misc = {
diff --git a/drivers/staging/dream/qdsp5/audio_in.c b/drivers/staging/dream/qdsp5/audio_in.c
index 6ae48e7..b51fa09 100644
--- a/drivers/staging/dream/qdsp5/audio_in.c
+++ b/drivers/staging/dream/qdsp5/audio_in.c
@@ -921,12 +921,14 @@ static struct file_operations audio_fops = {
 	.read		= audio_in_read,
 	.write		= audio_in_write,
 	.unlocked_ioctl	= audio_in_ioctl,
+	.llseek		= noop_llseek,
 };
 
 static struct file_operations audpre_fops = {
 	.owner          = THIS_MODULE,
 	.open           = audpre_open,
 	.unlocked_ioctl = audpre_ioctl,
+	.llseek		= noop_llseek,
 };
 
 struct miscdevice audio_in_misc = {
diff --git a/drivers/staging/dream/qdsp5/audio_mp3.c b/drivers/staging/dream/qdsp5/audio_mp3.c
index 530e1f3..409a19c 100644
--- a/drivers/staging/dream/qdsp5/audio_mp3.c
+++ b/drivers/staging/dream/qdsp5/audio_mp3.c
@@ -948,6 +948,7 @@ static struct file_operations audio_mp3_fops = {
 	.read		= audio_read,
 	.write		= audio_write,
 	.unlocked_ioctl	= audio_ioctl,
+	.llseek		= noop_llseek,
 };
 
 struct miscdevice audio_mp3_misc = {
diff --git a/drivers/staging/dream/qdsp5/audio_out.c b/drivers/staging/dream/qdsp5/audio_out.c
index 76d7fa5..d20e895 100644
--- a/drivers/staging/dream/qdsp5/audio_out.c
+++ b/drivers/staging/dream/qdsp5/audio_out.c
@@ -807,12 +807,14 @@ static struct file_operations audio_fops = {
 	.read		= audio_read,
 	.write		= audio_write,
 	.unlocked_ioctl	= audio_ioctl,
+	.llseek		= noop_llseek,
 };
 
 static struct file_operations audpp_fops = {
 	.owner		= THIS_MODULE,
 	.open		= audpp_open,
 	.unlocked_ioctl	= audpp_ioctl,
+	.llseek		= noop_llseek,
 };
 
 struct miscdevice audio_misc = {
diff --git a/drivers/staging/dream/qdsp5/audio_qcelp.c b/drivers/staging/dream/qdsp5/audio_qcelp.c
index effa96f..911bab4 100644
--- a/drivers/staging/dream/qdsp5/audio_qcelp.c
+++ b/drivers/staging/dream/qdsp5/audio_qcelp.c
@@ -824,6 +824,7 @@ static struct file_operations audio_qcelp_fops = {
 	.read = audqcelp_read,
 	.write = audqcelp_write,
 	.unlocked_ioctl = audqcelp_ioctl,
+	.llseek = noop_llseek,
 };
 
 struct miscdevice audio_qcelp_misc = {
diff --git a/drivers/staging/dream/qdsp5/evlog.h b/drivers/staging/dream/qdsp5/evlog.h
index 922ce67..e5ab86b 100644
--- a/drivers/staging/dream/qdsp5/evlog.h
+++ b/drivers/staging/dream/qdsp5/evlog.h
@@ -123,6 +123,7 @@ static int ev_log_open(struct inode *inode, struct file *file)
 static const struct file_operations ev_log_ops = {
 	.read = ev_log_read,
 	.open = ev_log_open,
+	.llseek = default_llseek,
 };
 
 static int ev_log_init(struct ev_log *log)
diff --git a/drivers/staging/dream/qdsp5/snd.c b/drivers/staging/dream/qdsp5/snd.c
index 037d7ff..e0f2f7b 100644
--- a/drivers/staging/dream/qdsp5/snd.c
+++ b/drivers/staging/dream/qdsp5/snd.c
@@ -247,6 +247,7 @@ static struct file_operations snd_fops = {
 	.open		= snd_open,
 	.release	= snd_release,
 	.unlocked_ioctl	= snd_ioctl,
+	.llseek		= noop_llseek,
 };
 
 struct miscdevice snd_misc = {
diff --git a/drivers/staging/frontier/alphatrack.c b/drivers/staging/frontier/alphatrack.c
index 4e52105..689099b 100644
--- a/drivers/staging/frontier/alphatrack.c
+++ b/drivers/staging/frontier/alphatrack.c
@@ -641,6 +641,7 @@ static const struct file_operations usb_alphatrack_fops = {
 	.open = usb_alphatrack_open,
 	.release = usb_alphatrack_release,
 	.poll = usb_alphatrack_poll,
+	.llseek = no_llseek,
 };
 
 /*
diff --git a/drivers/staging/frontier/tranzport.c b/drivers/staging/frontier/tranzport.c
index eed74f0..3d12c17 100644
--- a/drivers/staging/frontier/tranzport.c
+++ b/drivers/staging/frontier/tranzport.c
@@ -767,6 +767,7 @@ static const struct file_operations usb_tranzport_fops = {
 	.open = usb_tranzport_open,
 	.release = usb_tranzport_release,
 	.poll = usb_tranzport_poll,
+	.llseek = no_llseek,
 };
 
 /*
diff --git a/drivers/staging/iio/industrialio-core.c b/drivers/staging/iio/industrialio-core.c
index dd4d87a..92a212f 100644
--- a/drivers/staging/iio/industrialio-core.c
+++ b/drivers/staging/iio/industrialio-core.c
@@ -349,6 +349,7 @@ static const struct file_operations iio_event_chrdev_fileops = {
 	.release = iio_event_chrdev_release,
 	.open = iio_event_chrdev_open,
 	.owner = THIS_MODULE,
+	.llseek = noop_llseek,
 };
 
 static void iio_event_dev_release(struct device *dev)
diff --git a/drivers/staging/iio/industrialio-ring.c b/drivers/staging/iio/industrialio-ring.c
index 6ab578e..1c5f672 100644
--- a/drivers/staging/iio/industrialio-ring.c
+++ b/drivers/staging/iio/industrialio-ring.c
@@ -133,6 +133,7 @@ static const struct file_operations iio_ring_fileops = {
 	.release = iio_ring_release,
 	.open = iio_ring_open,
 	.owner = THIS_MODULE,
+	.llseek = noop_llseek,
 };
 
 /**
diff --git a/drivers/staging/lirc/lirc_imon.c b/drivers/staging/lirc/lirc_imon.c
index 6649325..ed5c5fe 100644
--- a/drivers/staging/lirc/lirc_imon.c
+++ b/drivers/staging/lirc/lirc_imon.c
@@ -115,7 +115,8 @@ static const struct file_operations display_fops = {
 	.owner		= THIS_MODULE,
 	.open		= &display_open,
 	.write		= &vfd_write,
-	.release	= &display_close
+	.release	= &display_close,
+	.llseek		= noop_llseek,
 };
 
 /*
diff --git a/drivers/staging/lirc/lirc_it87.c b/drivers/staging/lirc/lirc_it87.c
index ec11c0e..543c5c3b 100644
--- a/drivers/staging/lirc/lirc_it87.c
+++ b/drivers/staging/lirc/lirc_it87.c
@@ -342,6 +342,7 @@ static const struct file_operations lirc_fops = {
 	.unlocked_ioctl	= lirc_ioctl,
 	.open		= lirc_open,
 	.release	= lirc_close,
+	.llseek		= noop_llseek,
 };
 
 static int set_use_inc(void *data)
diff --git a/drivers/staging/lirc/lirc_sasem.c b/drivers/staging/lirc/lirc_sasem.c
index 73166c3..8f72a84 100644
--- a/drivers/staging/lirc/lirc_sasem.c
+++ b/drivers/staging/lirc/lirc_sasem.c
@@ -125,6 +125,7 @@ static const struct file_operations vfd_fops = {
 	.write		= &vfd_write,
 	.unlocked_ioctl	= &vfd_ioctl,
 	.release	= &vfd_close,
+	.llseek		= noop_llseek,
 };
 
 /* USB Device ID for Sasem USB Control Board */
diff --git a/drivers/staging/memrar/memrar_handler.c b/drivers/staging/memrar/memrar_handler.c
index a98b3f1..cfcaa8e 100644
--- a/drivers/staging/memrar/memrar_handler.c
+++ b/drivers/staging/memrar/memrar_handler.c
@@ -890,6 +890,7 @@ static const struct file_operations memrar_fops = {
 	.mmap           = memrar_mmap,
 	.open           = memrar_open,
 	.release        = memrar_release,
+	.llseek		= no_llseek,
 };
 
 static struct miscdevice memrar_miscdev = {
diff --git a/drivers/staging/panel/panel.c b/drivers/staging/panel/panel.c
index 3221814..6885f9a 100644
--- a/drivers/staging/panel/panel.c
+++ b/drivers/staging/panel/panel.c
@@ -1631,6 +1631,7 @@ static const struct file_operations keypad_fops = {
 	.read    = keypad_read,		/* read */
 	.open    = keypad_open,		/* open */
 	.release = keypad_release,	/* close */
+	.llseek  = default_llseek,
 };
 
 static struct miscdevice keypad_dev = {
diff --git a/drivers/staging/tidspbridge/rmgr/drv_interface.c b/drivers/staging/tidspbridge/rmgr/drv_interface.c
index 7ee8949..7b3a7d0 100644
--- a/drivers/staging/tidspbridge/rmgr/drv_interface.c
+++ b/drivers/staging/tidspbridge/rmgr/drv_interface.c
@@ -144,6 +144,7 @@ static const struct file_operations bridge_fops = {
 	.release = bridge_release,
 	.unlocked_ioctl = bridge_ioctl,
 	.mmap = bridge_mmap,
+	.llseek = noop_llseek,
 };
 
 #ifdef CONFIG_PM