From htejun@gmail.com Wed Jun 13 11:45:32 2007 From: Tejun Heo Cc: Tejun Heo , Greg Kroah-Hartman Subject: [PATCH 01/31] idr: fix obscure bug in allocation path Date: Thu, 14 Jun 2007 03:45:12 +0900 Message-Id: <11817603124037-git-send-email-htejun@gmail.com> To: greg@kroah.com, rjw@sisk.pl, akpm@linux-foundation.org, htejun@gmail.com From: Tejun Heo 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 Signed-off-by: Greg Kroah-Hartman --- lib/idr.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) --- a/lib/idr.c +++ b/lib/idr.c @@ -100,10 +100,11 @@ static int sub_alloc(struct idr *idp, vo 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, vo 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;