On 2/7/24 01:04, Amir Goldstein wrote: > On Wed, Feb 7, 2024 at 5:05 AM Antonio SJ Musumeci <trapexit@xxxxxxxxxx> wrote: >> >> On 2/6/24 00:53, Amir Goldstein wrote: > only for a specific inode object to which you have an open fd for. > Certainly not at the sb/mount level. > > Thanks, > Amir. Thanks again Amir. I've narrowed down the situation but I'm still struggling to pinpoint the specifics. And I'm unfortunately currently unable to replicate using any of the passthrough examples. Perhaps some feature I'm enabling (or not). My next steps are looking at exactly what differences there are in the INIT reply. I'm seeing a FUSE_LOOKUP request coming in for ".." of nodeid 1. I have my FUSE fs setup about as simply as I can. Single threaded. attr and entry/neg-entry caching off. direct-io on. EXPORT_SUPPORT is enabled. The mountpoint is exported via NFS. On the same host I mount NFS. I mount it on another host as well. On the local machine I loop reading a large file using dd (if=/mnt/nfs/file, of=/dev/null). After it finished I echo 3 > drop_caches. That alone will go forever. If on the second machine I start issuing `ls -lh /mnt/nfs` repeatedly after a moment it will trigger the issue. `ls` will successfully statx /mnt/nfs and the following openat and getdents also return successfully. As it iterates over the output of getdents statx's for directories fail with EIO and files succeed as normal. In my FUSE server for each EIO failure I'm seeing a lookup for ".." on nodeid 1. Afterwards all lookups fail on /mnt/nfs. The only request that seems to work is statfs. This was happening some time ago without me being able to reproduce it so I put a check to see if that was happening and return -ENOENT. However, looking over libfuse HLAPI it looks like fuse_lib_lookup doesn't handle this situation. Perhaps a segv waiting to happen? If I remove EXPORT_SUPPORT I'm no longer triggering the issue (which I guess makes sense.) Any ideas on how/why ".." for root node is coming in? Is that valid? It only happens when using NFS? I know there is talk of adding the ability of refusing export but what is the consequence of disabling EXPORT_SUPPORT? Is there a performance or capability difference? If it is a valid request what should I be returning? Thanks in advance.
