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Subject[PATCH ] mm/backing-dev.c: remove a null kfree and fix a false kmemleak in backing-dev
Date
It seems kfree(new_congested) does nothing since new_congested has already
been set null pointer before kfree, so remove it.

Meanwhile kmemleak reports the following memory leakage:

unreferenced object 0xcadbb440 (size 64):
comm "kworker/0:4", pid 1399, jiffies 4294946504 (age 808.290s)
hex dump (first 32 bytes):
00 00 00 00 01 00 00 00 00 00 00 00 01 00 00 00 ................
01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<c028fb64>] kmem_cache_alloc_trace+0x2c4/0x3cc
[<c025fe70>] wb_congested_get_create+0x9c/0x140
[<c0260100>] wb_init+0x184/0x1f4
[<c02601fc>] bdi_init+0x8c/0xd4
[<c051f75c>] blk_alloc_queue_node+0x9c/0x2d8
[<c05227e8>] blk_init_queue_node+0x2c/0x64
[<c052283c>] blk_init_queue+0x1c/0x20
[<c06c7b30>] __scsi_alloc_queue+0x28/0x44
[<c06caf4c>] scsi_alloc_queue+0x24/0x80
[<c06cc0b8>] scsi_alloc_sdev+0x21c/0x34c
[<c06ccc00>] scsi_probe_and_add_lun+0x878/0xb04
[<c06cd114>] __scsi_scan_target+0x288/0x59c
[<c06cd4b0>] scsi_scan_channel+0x88/0x9c
[<c06cd9b8>] scsi_scan_host_selected+0x118/0x130
[<c06cda70>] do_scsi_scan_host+0xa0/0xa4
[<c06cdbe4>] scsi_scan_host+0x170/0x1b4

wb_congested allocates memory for congested when wb_congested_get_create,
and release it when exit or failure by wb_congested_put.

Signed-off-by: Zumeng Chen <zumeng.chen@gmail.com>
---
mm/backing-dev.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index e19606b..d816b2a 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -457,6 +457,7 @@ wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)

/* allocate storage for new one and retry */
new_congested = kzalloc(sizeof(*new_congested), gfp);
+ kmemleak_ignore(new_congested);
if (!new_congested)
return NULL;

@@ -468,7 +469,6 @@ wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
found:
atomic_inc(&congested->refcnt);
spin_unlock_irqrestore(&cgwb_lock, flags);
- kfree(new_congested);
return congested;
}

--
2.7.4
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