[PATCH 0/2] btrfs: zoned: fix zone management on degraded filesystems

[PATCH 0/2] btrfs: zoned: fix zone management on degraded filesystems

[Johannes Thumshirn]

Two fixes around ZONE FINISH and ZONE ACTIVATE for multi device filesystems in
degraded mode.

Both times we're dereferencing the btrfs_device::zone_info pointer without
prior checking if the device is present.

Johannes Thumshirn (2):
  btrfs: zoned: fix zone activation with missing devices
  btrfs: zoned: fix zone finishing with missing devices

 fs/btrfs/zoned.c | 6 ++++++
 1 file changed, 6 insertions(+)

-- 
2.43.0

[PATCH 1/2] btrfs: zoned: fix zone activation with missing devices

[Johannes Thumshirn]

From: Johannes Thumshirn <johannes.thumshirn@wdc.com>

If btrfs_zone_activate() is called with a filesystem that has missing
devices (e.g. a RAID file system mounted in degraded mode) it is accessing
the btrfs_device::zone_info pointer, which will not be set if the device in
question is missing.

Check if the device is present (by checking if it has a valid block
device pointer associated) and if not, skip zone activation for it.

Fixes: f9a912a3c45f ("btrfs: zoned: make zone activation multi stripe capable")
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
---
 fs/btrfs/zoned.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index c21a97b32f9a..8924f58919e8 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -2110,6 +2110,9 @@ bool btrfs_zone_activate(struct btrfs_block_group *block_group)
 		physical = map->stripes[i].physical;
 		zinfo = device->zone_info;
 
+		if (!device->bdev)
+			continue;
+
 		if (zinfo->max_active_zones == 0)
 			continue;
 
-- 
2.43.0

[PATCH 2/2] btrfs: zoned: fix zone finishing with missing devices

[Johannes Thumshirn]

From: Johannes Thumshirn <johannes.thumshirn@wdc.com>

If do_zone_finish() is called with a filesystem that has missing devices
(e.g. a RAID file system mounted in degraded mode) it is accessing the
btrfs_device::zone_info pointer, which will not be set if the device
in question is missing.

Check if the device is present (by checking if it has a valid block device
pointer associated) and if not, skip zone finishing for it.

Fixes: 4dcbb8ab31c1 ("btrfs: zoned: make zone finishing multi stripe capable")
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
---
 fs/btrfs/zoned.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index 8924f58919e8..7c502192cd6b 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -2274,6 +2274,9 @@ static int do_zone_finish(struct btrfs_block_group *block_group, bool fully_writ
 		struct btrfs_zoned_device_info *zinfo = device->zone_info;
 		unsigned int nofs_flags;
 
+		if (!device->bdev)
+			continue;
+
 		if (zinfo->max_active_zones == 0)
 			continue;
 
-- 
2.43.0

Re: [PATCH 0/2] btrfs: zoned: fix zone management on degraded filesystems

[Naohiro Aota]

On Mon Mar 17, 2025 at 8:24 PM JST, Johannes Thumshirn wrote:
> Two fixes around ZONE FINISH and ZONE ACTIVATE for multi device filesystems in
> degraded mode.
>
> Both times we're dereferencing the btrfs_device::zone_info pointer without
> prior checking if the device is present.

At first, I thought, we should not write into a block group containing a
missing device. But, yeah, in the degraded mode, we are allowed to make
un-synced writing.

So, for the series

Reviewed-by: Naohiro Aota <naohiro.aota@wdc.com>

>
> Johannes Thumshirn (2):
>   btrfs: zoned: fix zone activation with missing devices
>   btrfs: zoned: fix zone finishing with missing devices
>
>  fs/btrfs/zoned.c | 6 ++++++
>  1 file changed, 6 insertions(+)

Re: [PATCH 0/2] btrfs: zoned: fix zone management on degraded filesystems

[Anand Jain]

On 17/3/25 19:24, Johannes Thumshirn wrote:
> Two fixes around ZONE FINISH and ZONE ACTIVATE for multi device filesystems in
> degraded mode.
> 
> Both times we're dereferencing the btrfs_device::zone_info pointer without
> prior checking if the device is present.
> 
> Johannes Thumshirn (2):
>    btrfs: zoned: fix zone activation with missing devices
>    btrfs: zoned: fix zone finishing with missing devices
> 
>   fs/btrfs/zoned.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 

Looks good for now.

Reviewed-by: Anand Jain <anand.jain@oracle.com>


PS:
We have been using either of these methods to identify the
missing device.

   test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state)

or

   device->bdev == NULL

IMO, it's a good idea to consolidate to the BTRFS_DEV_STATE_MISSING
flag. I have some incomplete patches for that. Also, I think we
should discuss how to handle reappearing devices;

Thanks, Anand