Messages in this thread Patch in this message | | | Date | Wed, 18 Apr 2001 18:43:17 +0200 | From | k.lichtenwalder@computer ... | Subject | patch: llseek for raw devices |
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Hi, this is my try for implementing the llseek operation on raw devices. The reason is that lseek does a check on the limits of the undlying filesystem and thus tends to err where the real device lies. Lseek check takes the /dev/raw/rawX filesystem as limiting factor, not the device that is bound to rawX. In my case I'm using a reiserfs (the old one) with 4G limits and thus can't do an llseek on DVD, resulting in an error half way through the film. This lseek was rigged together from the lseek from the memory device and from limit checkings from the rw_raw_dev function. I couldn't find any maintainer, so it's going to the list. (Alan, if you're going to add it to the -ac patches, it's against plain 2.4.3 raw.c. But this patch should apply without problems) (please watch the on long line below, will most probably get broken in transit)
Klaus
--- raw.c.orig Mon Oct 2 05:35:15 2000 +++ raw.c Wed Apr 18 18:28:55 2001 @@ -28,12 +28,14 @@ ssize_t raw_read(struct file *, char *, size_t, loff_t *); ssize_t raw_write(struct file *, const char *, size_t, loff_t *); +loff_t raw_lseek(struct file * , loff_t, int); int raw_open(struct inode *, struct file *); int raw_release(struct inode *, struct file *); int raw_ctl_ioctl(struct inode *, struct file *, unsigned int, unsigned long); static struct file_operations raw_fops = { + llseek: raw_lseek, read: raw_read, write: raw_write, open: raw_open, @@ -341,4 +342,46 @@ } return err; +} + + +loff_t raw_lseek(struct file * file, loff_t offset, int orig) +{ + int minor; + kdev_t dev; + unsigned long limit; + + int sector_size, sector_bits, sector_mask; + int max_sectors; + loff_t fpos; + + switch (orig) { + case 0: + fpos = offset; + break; + case 1: + fpos = file->f_pos + offset; + break; + default: + return -EINVAL; + } + + minor = MINOR(file->f_dentry->d_inode->i_rdev); + dev = to_kdev_t(raw_device_bindings[minor]->bd_dev); + sector_size = raw_device_sector_size[minor]; + sector_bits = raw_device_sector_bits[minor]; + sector_mask = sector_size- 1; + max_sectors = KIO_MAX_SECTORS >> (sector_bits - 9); + + if (blk_size[MAJOR(dev)]) + limit = (((loff_t) blk_size[MAJOR(dev)][MINOR(dev)]) << BLOCK_SIZE_BITS) >> sector_bits; + else + limit = INT_MAX; + if ((fpos & sector_mask)) + return -EINVAL; + if ((fpos >> sector_bits) >= limit) { + return -EINVAL; + } + file->f_pos = fpos; + return fpos; }
------------------------------------------------------------------------ Klaus Lichtenwalder, Dipl. Inform., http://www.webforum.de/Klaus/ Fax +49-(0)89-91072699 Lichtenwalder@ACM.org NIC: KL2100, KL76-RIPE K.Lichtenwalder@Computer.org PGP Key fingerprint = 2658 EA97 E1A1 2680 5ECA 0036 80F5 F250 3CF8 C2C7 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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