stat64 for over 2TB file returned invalid st_blocks

[Takashi Sato]

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).

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.

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).

I have some tested for a file whose size is 3TB on JFS filesystem.
The following is the patch.

Signed-off-by: Takashi Sato <sho@xxxxxxxxxxxxxxxxxx>

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
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