[PATCH 12/12] Avoid dereferencing bd_disk during swap_entry_free for network storage
From: Mel Gorman <mgorman@suse.de>
Date: 2012-06-22 14:33:10
Also in:
linux-mm, linux-nfs, lkml
Subsystem:
memory management, memory management - swap, the rest · Maintainers:
Andrew Morton, Chris Li, Kairui Song, Linus Torvalds
Commit [b3a27d: swap: Add swap slot free callback to block_device_operations] dereferences p->bdev->bd_disk but this is a NULL dereference if using swap-over-NFS. This patch checks SWP_BLKDEV on the swap_info_struct before dereferencing. With reference to this callback, Christoph Hellwig stated "Please just remove the callback entirely. It has no user outside the staging tree and was added clearly against the rules for that staging tree". This would also be my preference but there was not an obvious way of keeping zram in staging/ happy. Signed-off-by: Xiaotian Feng <redacted> Signed-off-by: Mel Gorman <mgorman@suse.de> Acked-by: Rik van Riel <redacted> --- mm/swapfile.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 1d77b13..f4c802d 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c@@ -549,7 +549,6 @@ static unsigned char swap_entry_free(struct swap_info_struct *p, /* free if no reference */ if (!usage) { - struct gendisk *disk = p->bdev->bd_disk; if (offset < p->lowest_bit) p->lowest_bit = offset; if (offset > p->highest_bit)
@@ -560,9 +559,11 @@ static unsigned char swap_entry_free(struct swap_info_struct *p, nr_swap_pages++; p->inuse_pages--; frontswap_invalidate_page(p->type, offset); - if ((p->flags & SWP_BLKDEV) && - disk->fops->swap_slot_free_notify) - disk->fops->swap_slot_free_notify(p->bdev, offset); + if (p->flags & SWP_BLKDEV) { + struct gendisk *disk = p->bdev->bd_disk; + if (disk->fops->swap_slot_free_notify) + disk->fops->swap_slot_free_notify(p->bdev, offset); + } } return usage;
--
1.7.9.2
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