Messages in this thread | | | Date | Wed, 4 Sep 2002 23:18:03 +0200 | From | Tomas Szepe <> | Subject | Re: [reiserfs-dev] Re: [PATCH] sparc32: wrong type of nlink_t |
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> >>> Against 2.4.20-pre5 - fix up the type of nlink_t. This makes jfs and > >>> reiserfs stop complaining about comparisons always turning up false > >>> due to limited range of data type. > >>> > >>>If you change this, you change the types exported to userspace > >>>which will break everything. > >>> > >>> > >>Right. Here's a corresponding reiserfs/jfs fix, then. I've checked the > >>constants aren't used for anything else except nlink overflow alerts. > >> > >> > > > >I don't like this fix. I know 32767 is a lot of links, but I don't like > >artificially lowering a limit like this just because one architecture > >defines nlink_t incorrectly. I'd rather get rid of the compiler warnings > >with a cast in the few places the limit is checked, even though that is > >a little bit ugly. > > > > > > > >>diff -urN linux-2.4.20-pre5/fs/jfs/jfs_filsys.h > >>linux-2.4.20-pre5.n/fs/jfs/jfs_filsys.h > >>--- linux-2.4.20-pre5/fs/jfs/jfs_filsys.h 2002-09-01 > >>11:31:44.000000000 +0200 > >>+++ linux-2.4.20-pre5.n/fs/jfs/jfs_filsys.h 2002-09-01 > >>11:30:13.000000000 +0200 > >>@@ -125,7 +125,8 @@ > >>#define MAXBLOCKSIZE 4096 > >>#define MAXFILESIZE ((s64)1 << 52) > >> > >>-#define JFS_LINK_MAX 65535 /* nlink_t is unsigned short > >>*/ > >>+/* the shortest nlink_t there is is sparc's signed short */ > >>+#define JFS_LINK_MAX 32767 > >> > >>/* Minimum number of bytes supported for a JFS partition */ > >>#define MINJFS (0x1000000) > >>diff -urN linux-2.4.20-pre5/include/linux/reiserfs_fs.h > >>linux-2.4.20-pre5.n/include/linux/reiserfs_fs.h > >>--- linux-2.4.20-pre5/include/linux/reiserfs_fs.h 2002-09-01 > >>11:31:45.000000000 +0200 > >>+++ linux-2.4.20-pre5.n/include/linux/reiserfs_fs.h 2002-09-01 > >>11:23:30.000000000 +0200 > >>@@ -1185,10 +1185,12 @@ > >>#define MAX_B_NUM MAX_UL_INT > >>#define MAX_FC_NUM MAX_US_INT > >> > >>- > >>-/* the purpose is to detect overflow of an unsigned short */ > >>-#define REISERFS_LINK_MAX (MAX_US_INT - 1000) > >>- > >>+/* the original purpose was to detect a possible overflow > >>+ * of an unsigned short nlink_t. However, there are archs > >>+ * that only provide a signed short nlink_t, so this will > >>+ * have to start ringing a wee bit earlier. > >>+ */ > >>+#define REISERFS_LINK_MAX (0x7fff - 1000) > >> > >>/* The following defines are used in reiserfs_insert_item and > >>reiserfs_append_item */ > >>#define REISERFS_KERNEL_MEM 0 /* reiserfs kernel memory > >>mode */ > >> > >> > > > >Thanks, > >Shaggy > > > > > > > I think you are sort of right. You are right to dislike this patch for > the reasons you state. The proper fix should be to make the result of > the limit computation be accurately architecture specific. I wasn't > paying enough attention --- hardcoding > > 0x7fff - 1000 > > is ugly. We need to find some appropriate #define to subtract 1000 from. > > Green, please scan the code for the magic constant to compute from, and > code something unless Dave or someone does it before you.
All right, how about this? ->
typedef unsigned long long u64;
/* usable for char, short int, and int */ #define set_to_max(a) \ { \ u64 max = ((u64) 2 << (sizeof(a) * 8 - 1)) - 1; \ a = max; if ((u64) a != max) a = max / 2; \ }
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