From f84adf4921ae3115502f44ff467b04bf2f88cf04 Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Wed, 13 Feb 2013 13:01:55 -0500 Subject: 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: [] 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 # .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 # .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 --- drivers/block/xen-blkfront.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) (limited to 'drivers/block/xen-blkfront.c') diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index 11043c1..c3dae2e 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); __free_page(pfn_to_page(persistent_gnt->pfn)); - 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; } -- cgit v1.1