ccing fs list
On 9/17/20 4:45 PM, Adrian Huang wrote:
From: Adrian Huang <ahuang12@xxxxxxxxxx>
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.JavaMail.zimbra@xxxxxxxxxx/
[2] https://lore.kernel.org/linux-nvdimm/alpine.LRH.2.02.2009141131220.30651@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
[3] https://lore.kernel.org/linux-nvdimm/CA+RJvhxBHriCuJhm-D8NvJRe3h2MLM+ZMFgjeJjrRPerMRLvdg@xxxxxxxxxxxxxx/
[4] https://lore.kernel.org/linux-nvdimm/20200903160608.GU878166@xxxxxxxxxxxxxxxxxxxxxxxxx/
Fixes: 6180bb446ab6 ("dax: fix detection of dax support for non-persistent memory block devices")
Reported-by: Yi Zhang <yi.zhang@xxxxxxxxxx>
Reported-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Signed-off-by: Adrian Huang <ahuang12@xxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: Coly Li <colyli@xxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: John Pittman <jpittman@xxxxxxxxxx>
Although I see that this is fix is already applied but ccing fsdevel and
ext4 since I ended up debugging and coming to the same conclusion as
this patch is fixing the recursion loop.
If not already applied then feel free to add:
Tested-by: Ritesh Harjani <riteshh@xxxxxxxxxxxxx>
---
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);
