path: root/drivers/block/xen-blkfront.c
diff options
authorKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2013-02-13 13:01:55 -0500
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2013-02-19 15:17:08 -0500
commitf84adf4921ae3115502f44ff467b04bf2f88cf04 (patch)
tree79a212e3c4fc0c11478370c15340e419ed66789b /drivers/block/xen-blkfront.c
parent01c681d4c70d64cb72142a2823f27c4146a02e63 (diff)
xen-blkfront: drop the use of llist_for_each_entry_safe
Replace llist_for_each_entry_safe with a while loop. llist_for_each_entry_safe can trigger a bug in GCC 4.1, so it's best to remove it and use a while loop and do the deletion manually. Specifically this bug can be triggered by hot-unplugging a disk, either by doing xm block-detach or by save/restore cycle. BUG: unable to handle kernel paging request at fffffffffffffff0 IP: [<ffffffffa0047223>] blkif_free+0x63/0x130 [xen_blkfront] The crash call trace is: ... bad_area_nosemaphore+0x13/0x20 do_page_fault+0x25e/0x4b0 page_fault+0x25/0x30 ? blkif_free+0x63/0x130 [xen_blkfront] blkfront_resume+0x46/0xa0 [xen_blkfront] xenbus_dev_resume+0x6c/0x140 pm_op+0x192/0x1b0 device_resume+0x82/0x1e0 dpm_resume+0xc9/0x1a0 dpm_resume_end+0x15/0x30 do_suspend+0x117/0x1e0 When drilling down to the assembler code, on newer GCC it does .L29: cmpq $-16, %r12 #, persistent_gnt check je .L30 #, out of the loop .L25: ... code in the loop testq %r13, %r13 # n je .L29 #, back to the top of the loop cmpq $-16, %r12 #, persistent_gnt check movq 16(%r12), %r13 # <variable>.node.next, n jne .L25 #, back to the top of the loop .L30: While on GCC 4.1, it is: L78: ... code in the loop testq %r13, %r13 # n je .L78 #, back to the top of the loop movq 16(%rbx), %r13 # <variable>.node.next, n jmp .L78 #, back to the top of the loop Which basically means that the exit loop condition instead of being: &(pos)->member != NULL; is: ; which makes the loop unbound. Since xen-blkfront is the only user of the llist_for_each_entry_safe macro remove it from llist.h. Orabug: 16263164 CC: stable@vger.kernel.org Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'drivers/block/xen-blkfront.c')
1 files changed, 10 insertions, 3 deletions
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 11043c18ac5..c3dae2e0f29 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -791,7 +791,7 @@ static void blkif_restart_queue(struct work_struct *work)
static void blkif_free(struct blkfront_info *info, int suspend)
struct llist_node *all_gnts;
- struct grant *persistent_gnt;
+ struct grant *persistent_gnt, *tmp;
struct llist_node *n;
/* Prevent new requests being issued until we fix things up. */
@@ -805,10 +805,17 @@ static void blkif_free(struct blkfront_info *info, int suspend)
/* Remove all persistent grants */
if (info->persistent_gnts_c) {
all_gnts = llist_del_all(&info->persistent_gnts);
- llist_for_each_entry_safe(persistent_gnt, n, all_gnts, node) {
+ persistent_gnt = llist_entry(all_gnts, typeof(*(persistent_gnt)), node);
+ while (persistent_gnt) {
gnttab_end_foreign_access(persistent_gnt->gref, 0, 0UL);
- kfree(persistent_gnt);
+ tmp = persistent_gnt;
+ n = persistent_gnt->node.next;
+ if (n)
+ persistent_gnt = llist_entry(n, typeof(*(persistent_gnt)), node);
+ else
+ persistent_gnt = NULL;
+ kfree(tmp);
info->persistent_gnts_c = 0;