Re: 64-bit stat (or not) in 32-bit Fedora binaries

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On 2/18/13 5:11 PM, John Reiser wrote:
> On 02/18/2013 01:33 PM, Eric Sandeen wrote:
>> XFS recently defaulted to allowing > 32 bit inode numbers, and btrfs can let inode numbers creep past 2^32 as well.
>>
>> While most applications don't care one bit about st_ino returned from a stat() call, the sad fact is that you'll get EOVERFLOW from stat32 if the inode number is too big to fit in 32 bits, even if you just wanted to get the file size.
> [snip]
>> Anyway, if you want to check your package(s) and maybe make them 64-bit-stat safe, the perl script above might help.  It's more than just -DFILE_OFFSET_BITS=64, since you'll need to be sure not to overflow any large values you get back from stat64 etc.
>>
>> Might be nice to get out ahead of this before, say, btrfs comes into wide use.  I don't know if there could be any more of a formal effort in this direction?
> 
>> p.s. here's a list of what was on my system that turned up hits:
> [snip list of several dozen packages that are affected]
> 
> 
> It would be useful to have a "backward compatibility" LD_PRELOAD shared
> library which intercepts the caller of stat32, and sets .st_ino to 0,
> without generating EOVERFLOW, whenever the actual inode number exceeds
> 32 bits.  This would allow the *option* of continued operation
> (postponing the work of portability enhancements) for the vast majority
> of packages which do use stat() but do not inspect .st_ino.

Yep, that would make some sense as a workaround.  FWIW, here's a systemtap
script which intercepts ext4 stat & bumps the inode nr past 2^32
(line numbers work on F18/kernel 3.7-8-ish at least)

probe kernel.statement("ext4_getattr@fs/ext4/inode.c+21")
{
	$stat->ino = $stat->ino + 4294967295;
}

probe begin { log("starting probe") }

it demonstrates the failures pretty well:

# stat testfile | grep Inode
Device: fd01h/64769d Inode: 281242      Links: 1

# stap -g change-ino.stp  &
[1] 5818
starting probe

# stat testfile | grep Inode
Device: fd01h/64769d Inode: 4295248537  Links: 1

# echo test | mail -s "does it work?" sandeen@xxxxxxxxxx
/etc/mail/sendmail.cf: line 0: cannot open: Value too large for defined data type
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