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fs: fix standard zero, full devices 

The standard devices are currently broken since they have
the size ~0. As now files use loff_t as file size which is a signed
type the read implementation gets confused and now returns -1.

The current implementation also has the (somewhat theorical) problem
that we do not have real streaming devices, so /dev/zero went out
of zeroes after reading 4GB (or now LLONG_MAX).

This patch introduces a new cdev flag DEVFS_IS_CHARACTER_DEV and a new
file size flag FILE_SIZE_STREAM which makes it possible to create
real stream devices instead.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
This commit is contained in:
Sascha Hauer 2012-07-03 10:12:40 +02:00
parent cca17e25bf
commit 8d064097eb
5 changed files with 11 additions and 8 deletions
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6
commands/stddev.c
View File

@ -40,7 +40,7 @@ static int zero_init(void)
cdev = xzalloc(sizeof (*cdev));
cdev->name = "zero";
cdev->size = ~0;
cdev->flags = DEVFS_IS_CHARACTER_DEV;
cdev->ops = &zeroops;
devfs_create(cdev);
@ -68,7 +68,7 @@ static int full_init(void)
cdev = xzalloc(sizeof (*cdev));
cdev->name = "full";
cdev->size = ~0;
cdev->flags = DEVFS_IS_CHARACTER_DEV;
cdev->ops = &fullops;
devfs_create(cdev);
@ -95,7 +95,7 @@ static int null_init(void)
cdev = xzalloc(sizeof (*cdev));
cdev->name = "null";
cdev->size = 0;
cdev->flags = DEVFS_IS_CHARACTER_DEV;
cdev->ops = &nullops;
devfs_create(cdev);

3
fs/devfs.c
View File

@ -121,7 +121,8 @@ static int devfs_open(struct device_d *_dev, FILE *f, const char *filename)
if (!cdev)
return -ENOENT;
f->size = cdev->size;
f->size = cdev->flags & DEVFS_IS_CHARACTER_DEV ?
FILE_SIZE_STREAM : cdev->size;
f->inode = cdev;
if (cdev->ops->open) {

8
fs/fs.c
View File

@ -643,7 +643,7 @@ int read(int fd, void *buf, size_t count)
fsdrv = dev_to_fs_driver(dev);
if (f->pos + count > f->size)
if (f->size != FILE_SIZE_STREAM && f->pos + count > f->size)
count = f->size - f->pos;
if (!count)
@ -672,7 +672,7 @@ ssize_t write(int fd, const void *buf, size_t count)
dev = f->dev;
fsdrv = dev_to_fs_driver(dev);
if (f->pos + count > f->size) {
if (f->size != FILE_SIZE_STREAM && f->pos + count > f->size) {
ret = fsdrv->truncate(dev, f, f->pos + count);
if (ret) {
if (ret != -ENOSPC)
@ -740,12 +740,12 @@ loff_t lseek(int fildes, loff_t offset, int whence)
switch (whence) {
case SEEK_SET:
if (offset > f->size)
if (f->size != FILE_SIZE_STREAM && offset > f->size)
goto out;
pos = offset;
break;
case SEEK_CUR:
if (offset + f->pos > f->size)
if (f->size != FILE_SIZE_STREAM && offset + f->pos > f->size)
goto out;
pos = f->pos + offset;
break;

1
include/driver.h
View File

@ -417,6 +417,7 @@ int cdev_erase(struct cdev *cdev, size_t count, loff_t offset);
#define DEVFS_PARTITION_FIXED (1 << 0)
#define DEVFS_PARTITION_READONLY (1 << 1)
#define DEVFS_IS_PARTITION (1 << 2)
#define DEVFS_IS_CHARACTER_DEV (1 << 3)
int devfs_add_partition(const char *devname, loff_t offset, loff_t size,
int flags, const char *name);

1
include/fs.h
View File

@ -24,6 +24,7 @@ typedef struct dir {
typedef struct filep {
struct device_d *dev; /* The device this FILE belongs to */
loff_t pos; /* current position in stream */
#define FILE_SIZE_STREAM ((loff_t) -1)
loff_t size; /* The size of this inode */
ulong flags; /* the O_* flags from open */