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    SubjectRe: [reiserfs-dev] Re: [PATCH] sparc32: wrong type of nlink_t
    > >>>  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; \
    }


    Tomas
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