| Message ID | 20081019132122.GA20282@www.tglx.de |
|---|---|
| State | RFC |
| Headers | show |
On Sun, 2008-10-19 at 15:21 +0200, Sebastian Andrzej Siewior wrote: > lstat() on /dev/ubi%d_%d returns 0 in the st_size field. This hack > allows to get the correct file size (as long as nobody updates the volume > in the meantime). > > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> > --- > I have userpsace programs which stat() the file and process the > returned number bytes. The other work around is to copy the file > somewhere and use this file instead of /dev/ubi. > Artem, do you thing it is possible to implement this functionality > properly or would it be reasonable not to use stat() at all on ubi > volumes? Hi, I've tried to stat various files in my /dev/ and all of them have size 0. Why UBI should be different? Indeed, stat should return size of the inode, that is normal semantics. You suggest making stat on UBI volume character devices return volume size. It might help your application, but it'll confuse other applications - for example 'du', which uses stat to calculate directory size. So am not sure it is good idea.
* Artem Bityutskiy | 2008-10-20 08:13:57 [+0300]: >Hi, Hi, >I've tried to stat various files in my /dev/ and all of them have size >0. None of them is a file filestem so no one of them returns something. >Why UBI should be different? As I made the patch I though that this is the expectingt behavior. sda/hda return 0 but those are larger then a few MiBs so you use a fs on top. So either nobody care(s|d) or it works as expected. >Indeed, stat should return size of the >inode, that is normal semantics. You suggest making stat on UBI volume >character devices return volume size. It might help your application, >but it'll confuse other applications - for example 'du', which uses stat >to calculate directory size. So am not sure it is good idea. It would report the size you would get after a read(). A cp()1 on ubi would copy the content of the node unless called with -a. I'm actually not sure what the expected behavior is. stat() returns information about a file and ubi isn't a regular file it is a character node. So it would be probably better to leave everything as it and change userspace instead. >Best regards, >Artem Bityutskiy (???????????????? ??????????) Sebastian
On Mon, 2008-10-20 at 11:11 +0200, Sebastian Andrzej Siewior wrote: > I'm actually not sure what the expected behavior is. stat() returns > information about a file and ubi isn't a regular file it is a character > node. So it would be probably better to leave everything as it and > change userspace instead. In my understanding, stat() should return how many bytes of data inode contains. Stat on a character device should return amount of bytes the character device inode contain. In ext3 major/minor are stored as meta-data, so it returns 0. Yes, I also think it is better if you amend your user-space application.
>>>>> "Artem" == Artem Bityutskiy <dedekind@infradead.org> writes: Hi, Artem> On Mon, 2008-10-20 at 11:11 +0200, Sebastian Andrzej Siewior wrote: >> I'm actually not sure what the expected behavior is. stat() returns >> information about a file and ubi isn't a regular file it is a character >> node. So it would be probably better to leave everything as it and >> change userspace instead. Artem> In my understanding, stat() should return how many bytes of Artem> data inode contains. Stat on a character device should return Artem> amount of bytes the character device inode contain. In ext3 Artem> major/minor are stored as meta-data, so it returns 0. Exactly. The normal way to know the size of these things is to open them and do the lseek(fd, 0, SEEK_END) thing.
diff --git a/drivers/mtd/ubi/cdev.c b/drivers/mtd/ubi/cdev.c index 03c759b..921dd81 100644 --- a/drivers/mtd/ubi/cdev.c +++ b/drivers/mtd/ubi/cdev.c @@ -123,6 +123,7 @@ static int vol_cdev_open(struct inode *inode, struct file *file) if (IS_ERR(desc)) return PTR_ERR(desc); + i_size_write(inode, desc->vol->used_bytes); file->private_data = desc; return 0; }
lstat() on /dev/ubi%d_%d returns 0 in the st_size field. This hack allows to get the correct file size (as long as nobody updates the volume in the meantime). Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- I have userpsace programs which stat() the file and process the returned number bytes. The other work around is to copy the file somewhere and use this file instead of /dev/ubi. Artem, do you thing it is possible to implement this functionality properly or would it be reasonable not to use stat() at all on ubi volumes? drivers/mtd/ubi/cdev.c | 1 + 1 files changed, 1 insertions(+), 0 deletions(-)