[PATCH] 2.2.18 ext2 large file bug?

[PATCH] 2.2.18 ext2 large file bug?

[Andreas Dilger]

Hello,
while looking at the COMPAT flag patches I made, I noticed the following
in the ext2/ext3 code.  I believe that this bug is fixed in 2.4, but it
also needs to be fixed in 2.2.  Basically, we are checking for an ext2
large file, which would be a file > 2GB on systems that don't support
such.  However, we are checking for a file > 8GB which is clearly wrong.
The ext3 version of the patch is also attached.

Cheers, Andreas
==========================================================================
--- linux-2.2.18pre27-TL/fs/ext2/file.c.orig	Mon Dec 11 22:43:17 2000
+++ linux-2.2.18pre27-TL/fs/ext2/file.c	Wed Dec 13 00:13:00 2000
@@ -208,7 +208,7 @@
 			if (!count)
 				return -EFBIG;
 		}
-		if (((pos + count) >> 31) &&
+		if (((pos + count) >> 33) &&
 		    !(sb->u.ext2_sb.s_es->s_feature_ro_compat &
 		      cpu_to_le32(EXT2_FEATURE_RO_COMPAT_LARGE_FILE))) {
 			/* If this is the first large file created, add a flag

--- linux-2.2.18pre27-TL/fs/ext3/file.c.orig	Mon Dec 11 22:43:17 2000
+++ linux-2.2.18pre27-TL/fs/ext3/file.c	Wed Dec 13 00:13:00 2000
@@ -208,7 +208,7 @@
 			if (!count)
 				return -EFBIG;
 		}
-		if (((pos + count) >> 31) &&
+		if (((pos + count) >> 33) &&
 		    !EXT3_HAS_RO_COMPAT_FEATURE(sb,
 					EXT3_FEATURE_RO_COMPAT_LARGE_FILE)) {
 			/* If this is the first large file created, add a flag
-- 
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert
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Re: [PATCH] 2.2.18 ext2 large file bug?

[Alexander Viro]

On Wed, 13 Dec 2000, Andreas Dilger wrote:

> Hello,
> while looking at the COMPAT flag patches I made, I noticed the following
> in the ext2/ext3 code.  I believe that this bug is fixed in 2.4, but it
> also needs to be fixed in 2.2.  Basically, we are checking for an ext2
> large file, which would be a file > 2GB on systems that don't support
> such.  However, we are checking for a file > 8GB which is clearly wrong.
> The ext3 version of the patch is also attached.
 
> Cheers, Andreas
> ==========================================================================
> --- linux-2.2.18pre27-TL/fs/ext2/file.c.orig	Mon Dec 11 22:43:17 2000
> +++ linux-2.2.18pre27-TL/fs/ext2/file.c	Wed Dec 13 00:13:00 2000
> @@ -208,7 +208,7 @@
>  			if (!count)
>  				return -EFBIG;
>  		}
> -		if (((pos + count) >> 31) &&
> +		if (((pos + count) >> 33) &&

	(x>>33) is the same as (x / (1LL<<33)). I.e. _with_ your change it
becomes "file >= 8Gb", instead of the current (correct) "file >= 2Gb".

							Cheers,
								Al
PS: Guys, 'fess up, who had written the following line?
                for (i = 0, ino = SYSV_ROOT_INO+1, block = sb->sv_firstinodezone, j = SYSV_ROOT_INO ; i < sb->sv_fic_size && block < sb->sv_firstdatazone ; block++, j = 0) {
And yes, that's one line. fs/sysv/ialloc.c...

-- 
Exercise 1-3. Read this code aloud:
? if ((falloc(SMRHSHSCRTCH, S_IFEXT|0644, MAXRODDHSH)) < 0)
?     ...
								K&P

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Re: [PATCH] 2.2.18 ext2 large file bug?

[Andreas Dilger]

Al Viro writes:
> 	(x>>33) is the same as (x / (1LL<<33)). I.e. _with_ your change it
> becomes "file >= 8Gb", instead of the current (correct) "file >= 2Gb".

OOPS.  My bad.  You are right.  Time to hide head in sand.

Cheers, Andreas
-- 
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert
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Re: [PATCH] 2.2.18 ext2 large file bug?

[Alan Cox]

> also needs to be fixed in 2.2.  Basically, we are checking for an ext2
> large file, which would be a file > 2GB on systems that don't support
> such.  However, we are checking for a file > 8GB which is clearly wrong.
> The ext3 version of the patch is also attached.

Umm..

	x>>33

is checking 8Gig

	x>>31 

is checking 2Gig

So your patch seems backwards

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Re: [PATCH] 2.2.18 ext2 large file bug?

[Alan Cox]

Umm ignore that my brain is backwards.

Alan

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