From: Adrian Huang <ahuang12(a)lenovo.com&gt; When mounting fsdax pmem device, commit 6180bb446ab6 ("dax: fix detection of dax support for non-persistent memory block devices") introduces the stack overflow [1][2]. Here is the call path for mounting ext4 file system: ext4_fill_super bdev_dax_supported __bdev_dax_supported dax_supported generic_fsdax_supported __generic_fsdax_supported bdev_dax_supported The call path leads to the infinite calling loop, so we cannot call bdev_dax_supported() in __generic_fsdax_supported(). The sanity checking of the variable 'dax_dev' is moved prior to the two bdev_dax_pgoff() checks [3][4]. [1] https://lore.kernel.org/linux-nvdimm/1420999447.1004543.1600055488770.Jav... [2] https://lore.kernel.org/linux-nvdimm/alpine.LRH.2.02.2009141131220.30651@... [3] https://lore.kernel.org/linux-nvdimm/CA+RJvhxBHriCuJhm-D8NvJRe3h2MLM+ZMFg... [4] https://lore.kernel.org/linux-nvdimm/20200903160608.GU878166@iweiny-DESK2... Fixes: 6180bb446ab6 ("dax: fix detection of dax support for non-persistent memory block devices") Reported-by: Yi Zhang <yi.zhang(a)redhat.com&gt; Reported-by: Mikulas Patocka <mpatocka(a)redhat.com&gt; Signed-off-by: Adrian Huang <ahuang12(a)lenovo.com&gt; Reviewed-by: Jan Kara <jack(a)suse.cz&gt; Cc: Coly Li <colyli(a)suse.de&gt; Cc: Ira Weiny <ira.weiny(a)intel.com&gt; Cc: John Pittman <jpittman(a)redhat.com&gt; --- Changelog: v3: 1. Add Reviewed-by from Jan 2. Add Reported-by 3. Replace lists.01.org with lore.kernel v2: Remove the checking for the returned value '-EOPNOTSUPP' of dax_direct_access(). Jan has prepared a patch to address the issue in dm. --- drivers/dax/super.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/drivers/dax/super.c b/drivers/dax/super.c index e5767c83ea23..11d0541e6f8f 100644 --- a/drivers/dax/super.c +++ b/drivers/dax/super.c @@ -85,6 +85,12 @@ bool __generic_fsdax_supported(struct dax_device *dax_dev, return false; } + if (!dax_dev) { + pr_debug("%s: error: dax unsupported by block device\n", + bdevname(bdev, buf)); + return false; + } + err = bdev_dax_pgoff(bdev, start, PAGE_SIZE, &pgoff); if (err) { pr_info("%s: error: unaligned partition for dax\n", @@ -100,12 +106,6 @@ bool __generic_fsdax_supported(struct dax_device *dax_dev, return false; } - if (!dax_dev || !bdev_dax_supported(bdev, blocksize)) { - pr_debug("%s: error: dax unsupported by block device\n", - bdevname(bdev, buf)); - return false; - } - id = dax_read_lock(); len = dax_direct_access(dax_dev, pgoff, 1, &kaddr, &pfn); len2 = dax_direct_access(dax_dev, pgoff_end, 1, &end_kaddr, &end_pfn); -- 2.17.1