On Thu, Jan 25, 2018 at 11:30 PM, Darrick J. Wong
<darrick.wong@xxxxxxxxxx> wrote:
> On Thu, Jan 25, 2018 at 11:21:38PM +0200, Amir Goldstein wrote:
>> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
>> ---
>>
>> Darrick,
>>
>> This patch fixes a problem I am hitting consistenty with xfstest
>> overlay/017 with certain overlay mount options (index=on,nfs_export=off).
>>
>> I see that overlayfs looks up in underlying xfs and gets a chardev
>> or blockdev inode with non initialized i_rdev (these are not whiteout
>> inodes).
>>
>> It takes a certain timing which happens in this test that does lookup
>> immediately after drop caches. The test causes a permanent error in
>> inode cache of xfs that is only fixed after another drop caches or
>> cycle mount.
>>
>> So I am certain there is a problem and that this patch fixes the
>> problem, I'm just not sure this is the right fix and if it is, which
>> is the commit that it "Fixes".
>
> We're basically reinitializing a VFS inode that was on its way to being
> reclaimed, which means that we don't xfs_iread. We still have to
> reinitialize the vfs inode state (because we'd already torn that down),
> so we have to preserve all the vfs inode state that the xfs inode stores
> in the vfs inode.
>
> Oh, right, hch moved if_rdev to i_rdev in 66f364649d870 ("xfs: remove
> if_rdev") but forgot the xfs_reinit_inode usage. so that would be the
> commit that this fixes. Doh.
>
Then this is a v4.15 regression fix and worth a last minute pull request IMO.
Devices may become unavailable under memory pressure... weird things can happen.
>
>>
>> Thanks,
>> Amir.
>>
>> fs/xfs/xfs_icache.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
>> index 3861d61fb265..3ce946063ffe 100644
>> --- a/fs/xfs/xfs_icache.c
>> +++ b/fs/xfs/xfs_icache.c
>> @@ -295,6 +295,7 @@ xfs_reinit_inode(
>> uint32_t generation = inode->i_generation;
>> uint64_t version = inode->i_version;
>> umode_t mode = inode->i_mode;
>> + dev_t dev = inode->i_rdev;
>>
>> error = inode_init_always(mp->m_super, inode);
>>
>> @@ -302,6 +303,7 @@ xfs_reinit_inode(
>> inode->i_generation = generation;
>> inode->i_version = version;
>> inode->i_mode = mode;
>> + inode->i_rdev = dev;
>> return error;
>> }
>>
>> --
>> 2.7.4
>>
>> --
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