On Wed, Feb 19 2025, Miklos Szeredi wrote:
> On Wed, 19 Feb 2025 at 12:23, Luis Henriques <luis@xxxxxxxxxx> wrote:
>
>> +static int fuse_notify_update_epoch(struct fuse_conn *fc)
>> +{
>> + struct fuse_mount *fm;
>> + struct inode *inode;
>> +
>> + inode = fuse_ilookup(fc, FUSE_ROOT_ID, &fm);
>> + if (!inode) || !fm)
>> + return -ENOENT;
>> +
>> + iput(inode);
>> + atomic_inc(&fc->epoch);
>> + shrink_dcache_sb(fm->sb);
>
> This is just an optimization and could be racy, kicking out valid
> cache (harmlessly of course). I'd leave it out of the first version.
OK, will do.
> There could be more than one fuse_mount instance. Wondering if epoch
> should be per-fm not per-fc...
Good question. Because the cache is shared among the several fuse_mount
instances the epoch may eventually affect all of them even if it's a
per-fm attribute. But on the other hand, different mounts could focus on
a different set of filesystem subtrees so... yeah, I'll probably leave it
in fc for now while thinking about it some more.
>> @@ -204,6 +204,12 @@ static int fuse_dentry_revalidate(struct inode *dir, const struct qstr *name,
>> int ret;
>>
>> inode = d_inode_rcu(entry);
>> + if (inode) {
>> + fm = get_fuse_mount(inode);
>> + if (entry->d_time < atomic_read(&fm->fc->epoch))
>> + goto invalid;
>> + }
>
> Negative dentries need to be invalidated too.
Ack.
>> @@ -446,6 +452,12 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
>> goto out_err;
>>
>> entry = newent ? newent : entry;
>> + if (inode) {
>> + struct fuse_mount *fm = get_fuse_mount(inode);
>> + entry->d_time = atomic_read(&fm->fc->epoch);
>> + } else {
>> + entry->d_time = 0;
>> + }
>
> Again, should do the same for positive and negative dentries.
>
> Need to read out fc->epoch before sending the request to the server,
> otherwise might get a stale dentry with an updated epoch.
Ah, good point.
> This also needs to be done in fuse_create_open(), create_new_entry()
> and fuse_direntplus_link().
Yeah I suspected there were a few other places where this would be
required. I'll look closer into that.
Thanks a lot for your feedback, Miklos. I'll work on this new approach,
so that I can send a real patch soon.
Cheers,
--
Luís
