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vfs: use 'unsigned long' accesses for dcache name comparison and hashing

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Ok, this is hacky, and only works on little-endian machines with goo
unaligned handling.  And even then only with CONFIG_DEBUG_PAGEALLOC
disabled, since it can access up to 7 bytes after the pathname.

But it runs like a bat out of hell.

Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Linus Torvalds 2012-03-06 11:16:17 -08:00
commit bfcfaa77bd
4 changed files with 150 additions and 0 deletions
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23
fs/dcache.c
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@ -144,6 +144,28 @@ int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
static inline int dentry_cmp(const unsigned char *cs, size_t scount,
const unsigned char *ct, size_t tcount)
{
#ifdef CONFIG_DCACHE_WORD_ACCESS
unsigned long a,b,mask;
if (unlikely(scount != tcount))
return 1;
for (;;) {
a = *(unsigned long *)cs;
b = *(unsigned long *)ct;
if (tcount < sizeof(unsigned long))
break;
if (unlikely(a != b))
return 1;
cs += sizeof(unsigned long);
ct += sizeof(unsigned long);
tcount -= sizeof(unsigned long);
if (!tcount)
return 0;
}
mask = ~(~0ul << tcount*8);
return unlikely(!!((a ^ b) & mask));
#else
if (scount != tcount)
return 1;
@ -155,6 +177,7 @@ static inline int dentry_cmp(const unsigned char *cs, size_t scount,
tcount--;
} while (tcount);
return 0;
#endif
}
static void __d_free(struct rcu_head *head)