From: Johannes Thumshirn <johannes.thumshirn@xxxxxxx> We have two reports of failed memory allocation in btrfs' code which is calling into report zones. Both of these reports have the following signature coming from __vmalloc_area_node(): kworker/u17:5: vmalloc error: size 0, failed to allocate pages, mode:0x10dc2(GFP_KERNEL|__GFP_HIGHMEM|__GFP_NORETRY|__GFP_ZERO), nodemask=(null),cpuset=/,mems_allowed=0 Further debugging showed these where allocations of one sector (512 bytes) and at least one of the reporter's systems where low on memory, so going through the overhead of allocating a vm area failed. Switching the allocation from __vmalloc() to kvzalloc() avoids the overhead of vmalloc() on small allocations and succeeds. Note: the buffer is already freed using kvfree() so there's no need to adjust the free path. Cc: Qu Wenru <wqu@xxxxxxxx> Cc: Naohiro Aota <naohiro.aota@xxxxxxx> Link: https://github.com/kdave/btrfs-progs/issues/779 Link: https://github.com/kdave/btrfs-progs/issues/915 Fixes: Fixes: 23a50861adda ("scsi: sd_zbc: Cleanup sd_zbc_alloc_report_buffer()") Signed-off-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx> --- Note2: one of the reporters tested the patch with kvmalloc(... , ... | __GFP_ZERO) instead of kvzalloc(). This is an "optimization" I did after the successful testing. Note3: calling report zones every time we create a block group in btrfs is suboptimal as well and we're going to change this code path as well ASAP. --- drivers/scsi/sd_zbc.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/scsi/sd_zbc.c b/drivers/scsi/sd_zbc.c index ee2b74238758..6ab27f4f4878 100644 --- a/drivers/scsi/sd_zbc.c +++ b/drivers/scsi/sd_zbc.c @@ -188,8 +188,7 @@ static void *sd_zbc_alloc_report_buffer(struct scsi_disk *sdkp, bufsize = min_t(size_t, bufsize, queue_max_segments(q) << PAGE_SHIFT); while (bufsize >= SECTOR_SIZE) { - buf = __vmalloc(bufsize, - GFP_KERNEL | __GFP_ZERO | __GFP_NORETRY); + buf = kvzalloc(bufsize, GFP_KERNEL | __GFP_NORETRY); if (buf) { *buflen = bufsize; return buf; -- 2.43.0
