On Thu, 2005-12-01 at 21:00 +0900, Takashi Sato wrote:
> Hi all,
>
> I found a problem at stat64 on 32bit architecture.
>
> When I called stat64 for a file which is larger than 2TB, stat64
> returned an invalid number of blocks at st_blocks on 32bit
> architecture, although it returned a valid number of blocks on 64bit
> architecture(ia64).
For jfs, it's a bigger problem than just stat64. When writing the inode
to disk, jfs calculates the number of blocks from the 32-bit value:
dip->di_nblocks = cpu_to_le64(PBLK2LBLK(ip->i_sb, ip->i_blocks))
So it won't only report the wrong number of blocks, but it will actually
store the wrong number. :-(
> The following describes the cause of this issue:
> i_blocks in inode is 4bytes on 32bit architecture. If it receives
> more than 2^32 number of blocks, it would overflow and set an
> invalid number to st_blocks.
>
> Below describes a sequence of setting overflowed inode.i_blocks
> to st_blocks through stat64.
>
> 1. generic_fillattr(struct inode *inode, struct kstat *stat)
> - Copy data from overflowed inode.i_blocks to kstat.blocks.
>
> 2. vfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
> struct kstat *stat)
> - Return invalid kstat.blocks to sys_stat64().
>
> 3. sys_stat64(char __user * filename, struct stat64 __user * statbuf)
> - Copy data from invalid kstat.blocks to stat64.st_blocks.
>
> I also found the following problem.
>
> - ioctl with FIOQSIZE command returns the size of file's data which
> has written to disk. The size of file's data is calculated as
> follows in inode_get_bytes().
>
> (((loff_t)inode->i_blocks) << 9) + inode->i_bytes
>
> On the file which is larger than 2TB, the ioctl will return an
> invalid size because i_blocks can't express the right number of
> blocks.
>
> I think the following modification is essential to fix these
> problems.
>
> 1. Change the type of inode.i_blocks and kstat.blocks from unsigned
> long to unsigned long long.
This would be okay.
> 2. Change the type of architecture dependent stat64.st_blocks in
> include/asm/asm-*/stat.h from unsigned long to unsigned long long.
> I tried modifying only stat64 of 32bit architecture
> (include/asm-i386/stat.h).
This changes the API, but the structure does suggest that the 4-byte pad
should be used for the high-order bytes of st_blocks, so that's not
really a problem. A correct fix would replace __pad4 with
st_blocks_high (or something like that) and ensure that the high-order
word was stored there. Your proposed fix would only be correct on
little-endian hardware, as Jörn pointed out.
> I have some tested for a file whose size is 3TB on JFS filesystem.
> The following is the patch.
>
> Signed-off-by: Takashi Sato <[email protected]>
>
> diff -uprN -X linux-2.6.14.org/Documentation/dontdiff linux-2.6.14.or
> g/include/asm-i386/stat.h linux-2.6.14-blocks/include/asm-i386/stat.h
> --- linux-2.6.14.org/include/asm-i386/stat.h 2005-10-28 09:02:08.000000000 +0900
> +++ linux-2.6.14-blocks/include/asm-i386/stat.h 2005-11-18 22:42:37.000000000 +0900
> @@ -58,8 +58,7 @@ struct stat64 {
> long long st_size;
> unsigned long st_blksize;
>
> - unsigned long st_blocks; /* Number 512-byte blocks allocated. */
> - unsigned long __pad4; /* future possible st_blocks high bits */
> + unsigned long long st_blocks; /* Number 512-byte blocks allocated. */
>
> unsigned long st_atime;
> unsigned long st_atime_nsec;
> diff -uprN -X linux-2.6.14.org/Documentation/dontdiff linux-2.6.14.or
> g/include/linux/fs.h linux-2.6.14-blocks/include/linux/fs.h
> --- linux-2.6.14.org/include/linux/fs.h 2005-10-28 09:02:08.000000000 +0900
> +++ linux-2.6.14-blocks/include/linux/fs.h 2005-11-18 17:08:03.000000000 +0900
> @@ -438,7 +438,7 @@ struct inode {
> unsigned int i_blkbits;
> unsigned long i_blksize;
> unsigned long i_version;
> - unsigned long i_blocks;
> + unsigned long long i_blocks;
> unsigned short i_bytes;
> spinlock_t i_lock; /* i_blocks, i_bytes, maybe i_size */
> struct semaphore i_sem;
> diff -uprN -X linux-2.6.14.org/Documentation/dontdiff linux-2.6.14.or
> g/include/linux/stat.h linux-2.6.14-blocks/include/linux/stat.h
> --- linux-2.6.14.org/include/linux/stat.h 2005-10-28 09:02:08.000000000 +0900
> +++ linux-2.6.14-blocks/include/linux/stat.h 2005-11-18 17:08:56.000000000 +0900
> @@ -69,7 +69,7 @@ struct kstat {
> struct timespec mtime;
> struct timespec ctime;
> unsigned long blksize;
> - unsigned long blocks;
> + unsigned long long blocks;
> };
>
> #endif
>
> Any feedback and comments are welcome.
>
> Best regards, Takashi Sato
--
David Kleikamp
IBM Linux Technology Center
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
