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idr: fix obscure bug in allocation path 

In sub_alloc(), when bitmap search fails, it goes up one level to
continue search.  This is done by updating the id cursor and searching
the upper level again.  If the cursor was at the end of the upper
level, we need to go further than that.

This wasn't implemented and when that happens the part of the cursor
which indexes into the upper level wraps and sub_alloc() ends up
searching the wrong bitmap.  It allocates id which doesn't match the
actual slot.

This patch fixes this by restarting from the top if the search needs
to go higher than one level.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Tejun Heo 2007-06-14 03:45:12 +09:00 committed by Greg Kroah-Hartman
parent dc0afa8388
commit 7aae6dd80e
1 changed files with 14 additions and 2 deletions
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16
lib/idr.c
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@ -100,10 +100,11 @@ static int sub_alloc(struct idr *idp, void *ptr, int *starting_id)
int n, m, sh;
struct idr_layer *p, *new;
struct idr_layer *pa[MAX_LEVEL];
int l, id;
int l, id, oid;
long bm;
id = *starting_id;
restart:
p = idp->top;
l = idp->layers;
pa[l--] = NULL;
@ -117,12 +118,23 @@ static int sub_alloc(struct idr *idp, void *ptr, int *starting_id)
if (m == IDR_SIZE) {
/* no space available go back to previous layer. */
l++;
oid = id;
id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;
/* if already at the top layer, we need to grow */
if (!(p = pa[l])) {
*starting_id = id;
return -2;
}
continue;
/* If we need to go up one layer, continue the
* loop; otherwise, restart from the top.
*/
sh = IDR_BITS * (l + 1);
if (oid >> sh == id >> sh)
continue;
else
goto restart;
}
if (m != n) {
sh = IDR_BITS*l;