On Mon, Nov 14, 2022 at 11:04 AM Benjamin Maynard <benmayn...@google.com> wrote: > > Hi Dave, > > I've added responses to your questions inline below. > > I also tried adding the noatime option to the mount on the source > filer as Jeff suggested, but this has not made any difference and the > issue is still persisting for me. > > I created the following diagram that explains my setup, and the exact > tests I am performing: > https://drive.google.com/file/d/12Xf-9yHCKM4eMr2YGqdSAVfGcximW4OG/view?usp=sharing. > > Hopefully this is clearer than my explanations below (let me know if > you'd prefer me to share an alternative way). > Yes, that's very helpful. Let me think about this one as I'm not sure. As Jeff says we may need tracepoints to track it down if I cannot repro it and/or nothing comes to mind.
> In order to remove the re-exporting layer of complexity, I also > performed the tests without the re-export server (architecture: > https://drive.google.com/file/d/1DQKhqo_UnQ8ul-z5Iram5LpisDmkKziQ/view?usp=share_link): > > Source NFS Server <-- Client (with FS-Cache) > > The same is happening, I cannot get FS-Cache to serve from cache. > Heavy writes, but no reads, even when the same file is copied many > times. > I'm pretty sure the above you're hitting the drop_caches / "fscache read optimisation" issue #1 I mentioned. I see dhowells just posted a v2 version of his previous patch: https://lore.kernel.org/linux-mm/166844174069.1124521.10890506360974169994.st...@warthog.procyon.org.uk/ I started with 6.1-rc5, added the above dhowells latest patch for that issue, and then my 5 patches on top. Then I added a small patch to utilize dhowells patch to ensure the read optimisation is removed. I ran my unit test that has been failing all along and as expected it passes with these patches. I pushed the series to github: https://github.com/DaveWysochanskiRH/kernel/commits/nfs-fscache-netfs https://github.com/DaveWysochanskiRH/kernel/commit/42f58f3d36d83839022dc2617bb6c2d1b09db65f I will also email you the series of patches on top of 6.1-rc5 so you can just apply from your mailbox if you want. > Hopefully something I am doing wrong on my end, but I can't figure out what. > > Kind Regards > Benjamin Maynard > > > On Mon, 14 Nov 2022 at 13:47, David Wysochanski <dwyso...@redhat.com> wrote: > > > > I apologize I did not read carefully enough and I missed some details > > in your original post. > > More below. > > > > On Sat, Nov 12, 2022 at 7:47 AM Benjamin Maynard <benmayn...@google.com> > > wrote: > > > > > > Hi all, > > > > > > I've been doing some more testing with these patches, I applied all of > > > the patches (v10 from > > > https://patchwork.kernel.org/project/linux-nfs/list/?series=691729) > > > apart from Patch 6 (the RFC patch) to version 6.0.8 of the kernel. > > > > > > I have the following setup: > > > > > > Source NFS Server <-- Re-Export Server (with FS-Cache) <-- NFS Client. > > > > > > I have a 500Gb file on the Source NFS Server, which I am then copying > > > to the NFS Client via the Re-Export Server. > > > > > > On the first copy, I see heavy writes to /var/cache/fscache on the > > > re-export server, and once the file copy completes I see that > > > /var/cache/fscache is approximately 500Gb in size. All good so far. > > > > > > I then deleted that file from the NFS Client, and dropped the caches > > > just to be safe (echo 3 > /proc/sys/vm/drop_caches on the NFS Client). > > > > > If you delete the file from the NFS client, how does that not delete the > > file from the original NFS server? > > Sorry - to be clear, I never deleted the file from the NFS mount > (which I know would in turn delete it from the re-export server and > the source filer). > > In order to perform the performance test, I copied the file from the > NFS mount on the NFS Client, to a local directory (cp > /mnt/nfs/500gb.img /tmp). > > When I said "I then deleted that file from the NFS Client", I meant I > deleted the local copy of that file. Not the file on the mount (rm > /tmp/500gb.img). > > Just to also stress, I have never dropped the caches on the Re-Export > Server (the one with FS-Cache) at any point in any of these tests, so > I don't think this is the problem. I have only ever dropped the caches > on the NFS client that is mounting the Re-Export Server. > > > > I then performed another copy of the 500Gb file on the NFS Client, > > > again via the Re-Export Server. What I expected would happen is that I > > > would see heavy reads from the /var/cache/fscache volume as the file > > > should be served from FS-Cache. > > > > > I don't understand this. When you say you "performed another copy" > > of what file? Wasn't the file deleted in the above step? > > As above, only the local copy was deleted. > > > > However what I actually saw was no reads whatsoever, FS-Cache seems to > > > be ignored and the file is pulled from the Source NFS Filer again. I > > > also see heavy writes to /var/cache/fscache, so it appears that > > > FS-Cache is overwriting its existing cache, and never using it. > > > > That would happen if the file was changed or re-created. > > > > > I only have 104Gb of memory on the Re-Export Server (with FS-Cache) so > > > it is not possible that the file is being served from the page cache. > > > > > > We saw this behaviour before on an older set of the patches when our > > > mount between the Re-Export Server and the Source NFS Filer was using > > > the "sync" option, but we are now using the "async" option and the > > > same is happening. > > > > > > Mount options: > > > > > > Source NFS Server <-- Re-Export Server (with FS-Cache): > > > > > > 10.0.0.49:/files /srv/nfs/files nfs > > > rw,noatime,vers=3,rsize=1048576,wsize=1048576,namlen=255,acregmin=600,acregmax=600,acdirmin=600,acdirmax=600,hard,nocto,proto=tcp,nconnect=16,timeo=600,retrans=2,sec=sys,mountaddr=10.0.0.49,mountvers=3,mountport=37485,mountproto=tcp,fsc,local_lock=none,addr=10.0.0.49 > > > > > > Re-Export Server (with FS-Cache) <-- NFS Client: > > > > > > 10.0.0.3:/files /mnt/nfs nfs > > > rw,relatime,vers=3,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=10.0.0.3,mountvers=3,mountport=20048,mountproto=tcp,local_lock=none,addr=10.0.0.3 > > > > > > It is also worth noting this behaviour is not unique to the re-export > > > use case. I see FS-Cache not being used with the following setup: > > > > > > Source NFS Server <-- Client (with FS-Cache). > > > > > > > This points at something more fundamental like something missed > > in the test or maybe a mount option. Can you explain what test > > you're doing here when you say "this behavior is not unique"? > > I've created the following diagram which explains the test I am > performing. I think it is a little easier to follow than explaining in > text. This should be viewable without any authentication: > https://drive.google.com/file/d/12Xf-9yHCKM4eMr2YGqdSAVfGcximW4OG/view?usp=sharing. > > By "this behaviour is not unique to the re-export use case" I mean > that the same happens if I remove the re-export server completely, and > just have the following setup: > > Source NFS Server <-- Client (with FS-Cache). > > > Can you show the mount options for both: > > - fscache filesystem on the re-export server (/var/cache/fscache) > > root@reexport:~$ mount | grep /var/cache/fscache > /dev/md127 on /var/cache/fscache type ext4 > (rw,relatime,discard,nobarrier,stripe=1024) > > > - exported filesystem on the NFS server (filesystem in /etc/exports) > > I have tried both: > > root@source:~$ mount | grep files > /dev/sdb1 on /files type ext4 (rw) > > root@source:~$ cat /etc/exports > /files > 10.0.0.0/8(rw,sync,wdelay,no_root_squash,no_all_squash,no_subtree_check,sec=sys,secure,nohide) > > and (at Jeff's suggestion): > > root@source:~$ mount | grep files > /dev/sdb1 on /files type ext4 (rw,noatime) > > root@source:~$ cat /etc/exports > /files > 10.0.0.0/8(rw,sync,wdelay,no_root_squash,no_all_squash,no_subtree_check,sec=sys,secure,nohide) > > > > Unfortunately the problem with drop_caches makes it more difficult > > to know when fscache is truly working. But some other unit test > > I have shows fscache does work with this patchset so I'm puzzled why > > you're not seeing it work at all. > > > > I pinged dhowells on the drop_caches issue so maybe we can get > > that one sorted out soon but I'm not sure since it's part of a series > > and proposes changes in mm. > > Just to be clear, I have never used drop_caches on the re-export > server in any of these tests. I have only ever done this on the NFS > Client. > > > > > > Thanks, > > > Ben > > > > > > > > > Kind Regards > > > > > > Benjamin Maynard > > > > > > Customer Engineer > > > > > > benmayn...@google.com > > > > > > Google, Inc. > > > > > > > > > > > > > > > On Mon, 31 Oct 2022 at 22:22, Trond Myklebust <tron...@hammerspace.com> > > > wrote: > > > > > > > > > > > > > > > > > On Oct 30, 2022, at 19:25, David Wysochanski <dwyso...@redhat.com> > > > > > wrote: > > > > > > > > > > On Sat, Oct 29, 2022 at 12:46 PM David Wysochanski > > > > > <dwyso...@redhat.com> wrote: > > > > >> > > > > >> On Fri, Oct 28, 2022 at 12:59 PM Trond Myklebust > > > > >> <tron...@kernel.org> wrote: > > > > >>> > > > > >>> On Fri, 2022-10-28 at 07:50 -0400, David Wysochanski wrote: > > > > >>>> On Thu, Oct 27, 2022 at 3:16 PM Trond Myklebust > > > > >>>> <tron...@kernel.org> > > > > >>>> wrote: > > > > >>>>> > > > > >>>>> On Mon, 2022-10-17 at 06:52 -0400, Dave Wysochanski wrote: > > > > >>>>>> Convert the NFS buffered read code paths to corresponding netfs > > > > >>>>>> APIs, > > > > >>>>>> but only when fscache is configured and enabled. > > > > >>>>>> > > > > >>>>>> The netfs API defines struct netfs_request_ops which must be > > > > >>>>>> filled > > > > >>>>>> in by the network filesystem. For NFS, we only need to define 5 > > > > >>>>>> of > > > > >>>>>> the functions, the main one being the issue_read() function. > > > > >>>>>> The issue_read() function is called by the netfs layer when a > > > > >>>>>> read > > > > >>>>>> cannot be fulfilled locally, and must be sent to the server > > > > >>>>>> (either > > > > >>>>>> the cache is not active, or it is active but the data is not > > > > >>>>>> available). > > > > >>>>>> Once the read from the server is complete, netfs requires a call > > > > >>>>>> to > > > > >>>>>> netfs_subreq_terminated() which conveys either how many bytes > > > > >>>>>> were > > > > >>>>>> read > > > > >>>>>> successfully, or an error. Note that issue_read() is called with > > > > >>>>>> a > > > > >>>>>> structure, netfs_io_subrequest, which defines the IO requested, > > > > >>>>>> and > > > > >>>>>> contains a start and a length (both in bytes), and assumes the > > > > >>>>>> underlying > > > > >>>>>> netfs will return a either an error on the whole region, or the > > > > >>>>>> number > > > > >>>>>> of bytes successfully read. > > > > >>>>>> > > > > >>>>>> The NFS IO path is page based and the main APIs are the pgio APIs > > > > >>>>>> defined > > > > >>>>>> in pagelist.c. For the pgio APIs, there is no way for the caller > > > > >>>>>> to > > > > >>>>>> know how many RPCs will be sent and how the pages will be broken > > > > >>>>>> up > > > > >>>>>> into underlying RPCs, each of which will have their own > > > > >>>>>> completion > > > > >>>>>> and > > > > >>>>>> return code. In contrast, netfs is subrequest based, a single > > > > >>>>>> subrequest may contain multiple pages, and a single subrequest is > > > > >>>>>> initiated with issue_read() and terminated with > > > > >>>>>> netfs_subreq_terminated(). > > > > >>>>>> Thus, to utilze the netfs APIs, NFS needs some way to accommodate > > > > >>>>>> the netfs API requirement on the single response to the whole > > > > >>>>>> subrequest, while also minimizing disruptive changes to the NFS > > > > >>>>>> pgio layer. > > > > >>>>>> > > > > >>>>>> The approach taken with this patch is to allocate a small > > > > >>>>>> structure > > > > >>>>>> for each nfs_netfs_issue_read() call, store the final error and > > > > >>>>>> number > > > > >>>>>> of bytes successfully transferred in the structure, and update > > > > >>>>>> these > > > > >>>>>> values > > > > >>>>>> as each RPC completes. The refcount on the structure is used as > > > > >>>>>> a > > > > >>>>>> marker > > > > >>>>>> for the last RPC completion, is incremented in > > > > >>>>>> nfs_netfs_read_initiate(), > > > > >>>>>> and decremented inside nfs_netfs_read_completion(), when a > > > > >>>>>> nfs_pgio_header > > > > >>>>>> contains a valid pointer to the data. On the final put (which > > > > >>>>>> signals > > > > >>>>>> the final outstanding RPC is complete) in > > > > >>>>>> nfs_netfs_read_completion(), > > > > >>>>>> call netfs_subreq_terminated() with either the final error value > > > > >>>>>> (if > > > > >>>>>> one or more READs complete with an error) or the number of bytes > > > > >>>>>> successfully transferred (if all RPCs complete successfully). > > > > >>>>>> Note > > > > >>>>>> that when all RPCs complete successfully, the number of bytes > > > > >>>>>> transferred > > > > >>>>>> is capped to the length of the subrequest. Capping the > > > > >>>>>> transferred > > > > >>>>>> length > > > > >>>>>> to the subrequest length prevents "Subreq overread" warnings from > > > > >>>>>> netfs. > > > > >>>>>> This is due to the "aligned_len" in nfs_pageio_add_page(), and > > > > >>>>>> the > > > > >>>>>> corner case where NFS requests a full page at the end of the > > > > >>>>>> file, > > > > >>>>>> even when i_size reflects only a partial page (NFS overread). > > > > >>>>>> > > > > >>>>>> Signed-off-by: Dave Wysochanski <dwyso...@redhat.com> > > > > >>>>>> Reviewed-by: Jeff Layton <jlay...@kernel.org> > > > > >>>>> > > > > >>>>> > > > > >>>>> This is not doing what I asked for, which was to separate out the > > > > >>>>> fscache functionality, so that we can call that if and when it is > > > > >>>>> available. > > > > >>>>> > > > > >>>> I must have misunderstood then. > > > > >>>> > > > > >>>> The last feedback I have from you was that you wanted it to be > > > > >>>> an opt-in feature, and it was a comment on a previous patch > > > > >>>> to Kconfig. I was proceeding the best I knew how, but > > > > >>>> let me try to get back on track. > > > > >>>> > > > > >>>>> Instead, it is just wrapping the NFS requests inside netfs > > > > >>>>> requests. As > > > > >>>>> it stands, that means it is just duplicating information, and > > > > >>>>> adding > > > > >>>>> unnecessary overhead to the standard I/O path (extra allocations, > > > > >>>>> extra > > > > >>>>> indirect calls, and extra bloat to the inode). > > > > >>>>> > > > > >>>> I think I understand what you're saying but I'm not sure. Let me > > > > >>>> ask some clarifying questions. > > > > >>>> > > > > >>>> Are you objecting to the code when CONFIG_NFS_FSCACHE is > > > > >>>> configured? Or when it is not? Or both? I think you're objecting > > > > >>>> when it's configured, but not enabled (we mount without 'fsc'). > > > > >>>> Am I right? > > > > >>>> > > > > >>>> Also, are you objecting to the design that to use fcache we now > > > > >>>> have to use netfs, specifically: > > > > >>>> - call into netfs via either netfs_read_folio or netfs_readahead > > > > >>>> - if fscache is enabled, then the IO can be satisfied from fscache > > > > >>>> - if fscache is not enabled, or some of the IO cannot be satisfied > > > > >>>> from the cache, then NFS is called back via netfs_issue_read > > > > >>>> and we use the normal NFS read pageio interface. This requires > > > > >>>> we call netfs_subreq_terminated() when all the RPCs complete, > > > > >>>> which is the reason for the small changes to pagelist.c > > > > >>> > > > > >>> I'm objecting to any middle layer "solution" that adds overhead to > > > > >>> the > > > > >>> NFS I/O paths. > > > > >>> > > > > >> Got it. > > > > >> > > > > >>> I'm willing to consider solutions that are specific only to the > > > > >>> fscache > > > > >>> use case (i.e. when the 'fsc' mount option is specified). However > > > > >>> when > > > > >>> I perform a normal NFS mount, and do I/O, then I don't want to see > > > > >>> extra memory allocations, extra indirect calls and larger inode > > > > >>> footprints. > > > > >>> > > > > >>> IOW: I want the code to optimise for the case of standard NFS, not > > > > >>> for > > > > >>> the case of 'NFS with cachefs additions'. > > > > >>> > > > > >> I agree completely. Are you seeing extra memory allocations > > > > >> happen on mounts without 'fsc' or is it more a concern or how > > > > >> some of the patches look? We should not be calling any netfs or > > > > >> fscache code if 'fsc' is not on the mount and I don't see any in my > > > > >> testing. So either there's a misunderstanding here, or there's a > > > > >> bug I'm missing. > > > > >> > > > > >> If fscache is not configured, then nfs_netfs_read_folio() and > > > > >> nfs_netfs_readahead() is a wrapper that returns -ENOBUFS. > > > > >> If it's configured but not enabled, then the checks for > > > > >> netfs_inode(inode)->cache should skip over any netfs code. > > > > >> But maybe there's a non-obvious bug you're seeing and > > > > >> somehow netfs is still getting called? Because I cannot > > > > >> see netfs getting called if 'fsc' is not on the mount in my > > > > >> tests. > > > > >> > > > > >> int nfs_netfs_read_folio(struct file *file, struct folio *folio) > > > > >> { > > > > >> if (!netfs_inode(folio_inode(folio))->cache) > > > > >> return -ENOBUFS; > > > > >> > > > > >> return netfs_read_folio(file, folio); > > > > >> } > > > > >> > > > > >> int nfs_netfs_readahead(struct readahead_control *ractl) > > > > >> { > > > > >> struct inode *inode = ractl->mapping->host; > > > > >> > > > > >> if (!netfs_inode(inode)->cache) > > > > >> return -ENOBUFS; > > > > >> > > > > >> netfs_readahead(ractl); > > > > >> return 0; > > > > >> } > > > > >> > > > > >> > > > > >>>> > > > > >>>> Can you be more specific as to the portions of the patch you don't > > > > >>>> like > > > > >>>> so I can move it in the right direction? > > > > >>>> > > > > >>>> This is from patch #2 which you didn't comment on. I'm not sure > > > > >>>> you're > > > > >>>> ok with it though, since you mention "extra bloat to the inode". > > > > >>>> Do you object to this even though it's wrapped in an > > > > >>>> #ifdef CONFIG_NFS_FSCACHE? If so, do you require no > > > > >>>> extra size be added to nfs_inode? > > > > >>>> > > > > >>>> @@ -204,9 +208,11 @@ struct nfs_inode { > > > > >>>> __u64 write_io; > > > > >>>> __u64 read_io; > > > > >>>> #ifdef CONFIG_NFS_FSCACHE > > > > >>>> - struct fscache_cookie *fscache; > > > > >>>> -#endif > > > > >>>> + struct netfs_inode netfs; /* netfs context and VFS > > > > >>>> inode > > > > >>>> */ > > > > >>>> +#else > > > > >>>> struct inode vfs_inode; > > > > >>>> +#endif > > > > >>>> + > > > > >>> > > > > >>> Ideally, I'd prefer no extra size. I can live with it up to a > > > > >>> certain > > > > >>> point, however for now NFS is not unconditionally opting into the > > > > >>> netfs > > > > >>> project. If we're to ever do that, then I want to see streamlined > > > > >>> code > > > > >>> for the standard I/O case. > > > > >>> > > > > >> Ok and understood about standard I/O case. > > > > >> > > > > >> I was thinking how we might not increase the size, but I don't think > > > > >> I can make it work. > > > > >> > > > > >> I thought we could change to something like the below, without an > > > > >> embedded struct inode: > > > > >> > > > > >> @@ -204,9 +208,11 @@ struct nfs_inode { > > > > >> __u64 write_io; > > > > >> __u64 read_io; > > > > >> #ifdef CONFIG_NFS_FSCACHE > > > > >> - struct fscache_cookie *fscache; > > > > >> -#endif > > > > >> + struct netfs_inode *netfs; /* netfs context and VFS > > > > >> inode */ > > > > >> +#else > > > > >> struct inode vfs_inode; > > > > >> +#endif > > > > >> + > > > > >> > > > > >> Then I would need to alloc/free a netfs_inode at the time of > > > > >> nfs_inode initiation. Unfortunately this has the issue that the > > > > >> NFS_I() > > > > >> macro cannot work, because it requires an embedded "struct inode" > > > > >> due to "container_of" use: > > > > >> > > > > >> +#ifdef CONFIG_NFS_FSCACHE > > > > >> +static inline struct inode *VFS_I(struct nfs_inode *nfsi) > > > > >> +{ > > > > >> + return &nfsi->netfs.inode; > > > > >> +} > > > > >> +static inline struct nfs_inode *NFS_I(const struct inode *inode) > > > > >> +{ > > > > >> + return container_of(inode, struct nfs_inode, netfs.inode); > > > > >> +} > > > > >> +#else > > > > >> +static inline struct inode *VFS_I(struct nfs_inode *nfsi) > > > > >> +{ > > > > >> + return &nfsi->vfs_inode; > > > > >> +} > > > > >> static inline struct nfs_inode *NFS_I(const struct inode *inode) > > > > >> { > > > > >> return container_of(inode, struct nfs_inode, vfs_inode); > > > > >> } > > > > >> +#endif > > > > >> > > > > >> > > > > > > > > > > Actually Trond maybe we can achieve a "0 length increase" of > > > > > nfs_inode if dhowells would take a patch to modify the definition > > > > > of struct netfs_inode and netfs_inode_init(), something like the WIP > > > > > patch below. What do you think? > > > > > > > > That works for me. > > > > > > > > > > > > > > I think maybe this could be a follow-on patch and if you/dhowells > > > > > think it's an ok idea I can try to work out what is needed across > > > > > the tree. I thought about it more and I kinda agree that in the > > > > > case for NFS where fscache is "configured but not enabled", > > > > > then even though we're only adding 24 bytes to the nfs_inode > > > > > each time, it will add up so it is worth at least a discussion. > > > > > > > > > > diff --git a/include/linux/netfs.h b/include/linux/netfs.h > > > > > index f2402ddeafbf..195714f1c355 100644 > > > > > --- a/include/linux/netfs.h > > > > > +++ b/include/linux/netfs.h > > > > > @@ -118,11 +118,7 @@ enum netfs_io_source { > > > > > typedef void (*netfs_io_terminated_t)(void *priv, ssize_t > > > > > transferred_or_error, > > > > > bool was_async); > > > > > > > > > > -/* > > > > > - * Per-inode context. This wraps the VFS inode. > > > > > - */ > > > > > -struct netfs_inode { > > > > > - struct inode inode; /* The VFS inode */ > > > > > +struct netfs_info { > > > > > const struct netfs_request_ops *ops; > > > > > #if IS_ENABLED(CONFIG_FSCACHE) > > > > > struct fscache_cookie *cache; > > > > > @@ -130,6 +126,14 @@ struct netfs_inode { > > > > > loff_t remote_i_size; /* Size of the remote > > > > > file */ > > > > > }; > > > > > > > > > > +/* > > > > > + * Per-inode context. This wraps the VFS inode. > > > > > + */ > > > > > +struct netfs_inode { > > > > > + struct inode inode; /* The VFS inode */ > > > > > + struct netfs_info *netfs; /* Rest of netfs data > > > > > */ > > > > > +}; > > > > > + > > > > > /* > > > > > * Resources required to do operations on a cache. > > > > > */ > > > > > @@ -312,10 +316,12 @@ static inline struct netfs_inode > > > > > *netfs_inode(struct inode *inode) > > > > > static inline void netfs_inode_init(struct netfs_inode *ctx, > > > > > const struct netfs_request_ops *ops) > > > > > { > > > > > - ctx->ops = ops; > > > > > - ctx->remote_i_size = i_size_read(&ctx->inode); > > > > > + ctx->netfs = kzalloc(sizeof(struct netfs_info)), GFP_KERNEL); > > > > > + /* FIXME: Check for NULL */ > > > > > + ctx->netfs->ops = ops; > > > > > + ctx->netfs->remote_i_size = i_size_read(&ctx->inode); > > > > > #if IS_ENABLED(CONFIG_FSCACHE) > > > > > - ctx->cache = NULL; > > > > > + ctx->netfs->cache = NULL; > > > > > #endif > > > > > } > > > > > > > > > > > > > > > > > > > >> > > > > >>>> > > > > >>>> > > > > >>>> Are you ok with the stub functions which are placed in fscache.h, > > > > >>>> and > > > > >>>> when CONFIG_NFS_FSCACHE is not set, become either a no-op > > > > >>>> or a 1-liner (nfs_netfs_readpage_release)? > > > > >>>> > > > > >>>> #else /* CONFIG_NFS_FSCACHE */ > > > > >>>> +static inline void nfs_netfs_inode_init(struct nfs_inode *nfsi) {} > > > > >>>> +static inline void nfs_netfs_initiate_read(struct nfs_pgio_header > > > > >>>> *hdr) {} > > > > >>>> +static inline void nfs_netfs_read_completion(struct > > > > >>>> nfs_pgio_header > > > > >>>> *hdr) {} > > > > >>>> +static inline void nfs_netfs_readpage_release(struct nfs_page > > > > >>>> *req) > > > > >>>> +{ > > > > >>>> + unlock_page(req->wb_page); > > > > >>>> +} > > > > >>>> static inline void nfs_fscache_release_super_cookie(struct > > > > >>>> super_block *sb) {} > > > > >>>> static inline void nfs_fscache_init_inode(struct inode *inode) {} > > > > >>>> > > > > >>>> > > > > >>>> Do you object to the below? If so, then do you want > > > > >>>> #ifdef CONFIG_NFS_FSCACHE here? > > > > >>>> > > > > >>>> -- a/fs/nfs/inode.c > > > > >>>> +++ b/fs/nfs/inode.c > > > > >>>> @@ -2249,6 +2249,8 @@ struct inode *nfs_alloc_inode(struct > > > > >>>> super_block *sb) > > > > >>>> #ifdef CONFIG_NFS_V4_2 > > > > >>>> nfsi->xattr_cache = NULL; > > > > >>>> #endif > > > > >>>> + nfs_netfs_inode_init(nfsi); > > > > >>>> + > > > > >>>> return VFS_I(nfsi); > > > > >>>> } > > > > >>>> EXPORT_SYMBOL_GPL(nfs_alloc_i > > > > >>>> node); > > > > >>>> > > > > >>>> > > > > >>>> Do you object to the changes in fs/nfs/read.c? Specifically, > > > > >>>> how about the below calls to netfs from nfs_read_folio and > > > > >>>> nfs_readahead into equivalent netfs calls? So when > > > > >>>> NFS_CONFIG_FSCACHE is set, but fscache is not enabled > > > > >>>> ('fsc' not on mount), these netfs functions do immediately call > > > > >>>> netfs_alloc_request(). But I wonder if we could simply add a > > > > >>>> check to see if fscache is enabled on the mount, and skip > > > > >>>> over to satisfy what you want. Am I understanding what you > > > > >>>> want? > > > > >>> > > > > >>> Quite frankly, I'd prefer that we just split out the functionality > > > > >>> that > > > > >>> is needed from the netfs code so that it can be optimised. However > > > > >>> I'm > > > > >>> not interested enough in the cachefs functionality to work on that > > > > >>> myself. ...and as I indicated above, I might be OK with opting into > > > > >>> the > > > > >>> netfs project, once the overhead can be made to disappear. > > > > >>> > > > > >> Understood. > > > > >> > > > > >> If you think it makes more sense, I can move some of the nfs_netfs_* > > > > >> functions into a netfs.c file as a starting point. Or that can maybe > > > > >> be done in a future patchset? > > > > >> > > > > >> For now I was equating netfs and fscache together so we can > > > > >> move on from the much older and single-page limiting fscache > > > > >> interface that is likely to go away soon. > > > > >> > > > > >>>> > > > > >>>> @@ -355,6 +343,10 @@ int nfs_read_folio(struct file *file, struct > > > > >>>> folio *folio) > > > > >>>> if (NFS_STALE(inode)) > > > > >>>> goto out_unlock; > > > > >>>> > > > > >>>> + ret = nfs_netfs_read_folio(file, folio); > > > > >>>> + if (!ret) > > > > >>>> + goto out; > > > > >>>> + > > > > >>>> > > > > >>>> @@ -405,6 +399,10 @@ void nfs_readahead(struct readahead_control > > > > >>>> *ractl) > > > > >>>> if (NFS_STALE(inode)) > > > > >>>> goto out; > > > > >>>> > > > > >>>> + ret = nfs_netfs_readahead(ractl); > > > > >>>> + if (!ret) > > > > >>>> + goto out; > > > > >>>> + > > > > >>>> > > > > >> The above wrappers should prevent any additional overhead when > > > > >> fscache > > > > >> is not enabled. As far as I know these work to avoid calling netfs > > > > >> when 'fsc' is not on the mount. > > > > >> > > > > >>>> > > > > >>>> And how about these calls from different points in the read > > > > >>>> path to the earlier mentioned stub functions? > > > > >>>> > > > > >>>> @@ -110,20 +110,13 @@ EXPORT_SYMBOL_GPL(nfs_pageio_reset_read_mds); > > > > >>>> > > > > >>>> static void nfs_readpage_release(struct nfs_page *req, int error) > > > > >>>> { > > > > >>>> - struct inode *inode = > > > > >>>> d_inode(nfs_req_openctx(req)->dentry); > > > > >>>> struct page *page = req->wb_page; > > > > >>>> > > > > >>>> - dprintk("NFS: read done (%s/%llu %d@%lld)\n", inode->i_sb- > > > > >>>>> s_id, > > > > >>>> - (unsigned long long)NFS_FILEID(inode), > > > > >>>> req->wb_bytes, > > > > >>>> - (long long)req_offset(req)); > > > > >>>> - > > > > >>>> if (nfs_error_is_fatal_on_server(error) && error != - > > > > >>>> ETIMEDOUT) > > > > >>>> SetPageError(page); > > > > >>>> - if (nfs_page_group_sync_on_bit(req, PG_UNLOCKPAGE)) { > > > > >>>> - if (PageUptodate(page)) > > > > >>>> - nfs_fscache_write_page(inode, page); > > > > >>>> - unlock_page(page); > > > > >>>> - } > > > > >>>> + if (nfs_page_group_sync_on_bit(req, PG_UNLOCKPAGE)) > > > > >>>> + nfs_netfs_readpage_release(req); > > > > >>>> + > > > > >>> > > > > >>> I'm not seeing the value of wrapping unlock_page(), no... That code > > > > >>> is > > > > >>> going to need to change when we move it to use folios natively > > > > >>> anyway. > > > > >>> > > > > >> Ok, how about I make it conditional on whether fscache is configured > > > > >> and enabled then, similar to the nfs_netfs_read_folio() and > > > > >> nfs_netfs_readahead()? Below is what that would look like. > > > > >> I could inline the code in nfs_netfs_readpage_release() if you > > > > >> think it would be clearer. > > > > >> > > > > >> static void nfs_readpage_release(struct nfs_page *req, int error) > > > > >> { > > > > >> struct page *page = req->wb_page; > > > > >> > > > > >> if (nfs_error_is_fatal_on_server(error) && error != -ETIMEDOUT) > > > > >> SetPageError(page); > > > > >> if (nfs_page_group_sync_on_bit(req, PG_UNLOCKPAGE)) > > > > >> #ifndef CONFIG_NFS_FSCACHE > > > > >> unlock_page(req->wb_page); > > > > >> #else > > > > >> nfs_netfs_readpage_release(req); > > > > >> #endif > > > > >> nfs_release_request(req); > > > > >> } > > > > >> > > > > >> > > > > >> void nfs_netfs_readpage_release(struct nfs_page *req) > > > > >> { > > > > >> struct inode *inode = d_inode(nfs_req_openctx(req)->dentry); > > > > >> > > > > >> /* > > > > >> * If fscache is enabled, netfs will unlock pages. > > > > >> */ > > > > >> if (netfs_inode(inode)->cache) > > > > >> return; > > > > >> > > > > >> unlock_page(req->wb_page); > > > > >> } > > > > >> > > > > >> > > > > >>>> nfs_release_request(req); > > > > >>>> } > > > > >>>> > > > > >>>> @@ -177,6 +170,8 @@ static void nfs_read_completion(struct > > > > >>>> nfs_pgio_header *hdr) > > > > >>>> nfs_list_remove_request(req); > > > > >>>> nfs_readpage_release(req, error); > > > > >>>> } > > > > >>>> + nfs_netfs_read_completion(hdr); > > > > >>>> + > > > > >>>> out: > > > > >>>> hdr->release(hdr); > > > > >>>> } > > > > >>>> @@ -187,6 +182,7 @@ static void nfs_initiate_read(struct > > > > >>>> nfs_pgio_header *hdr, > > > > >>>> struct rpc_task_setup *task_setup_data, > > > > >>>> int how) > > > > >>>> { > > > > >>>> rpc_ops->read_setup(hdr, msg); > > > > >>>> + nfs_netfs_initiate_read(hdr); > > > > >>>> trace_nfs_initiate_read(hdr); > > > > >>>> } > > > > >>>> > > > > >>>> > > > > >>>> Are you ok with these additions? Something like this would > > > > >>>> be required in the case of fscache configured and enabled, > > > > >>>> because we could have some of the data in a read in > > > > >>>> fscache, and some not. That is the reason for the netfs > > > > >>>> design, and why we need to be able to call the normal > > > > >>>> NFS read IO path (netfs calls into issue_read, and we call > > > > >>>> back via netfs_subreq_terminated)? > > > > >>>> > > > > >>>> @@ -101,6 +101,9 @@ struct nfs_pageio_descriptor { > > > > >>>> struct pnfs_layout_segment *pg_lseg; > > > > >>>> struct nfs_io_completion *pg_io_completion; > > > > >>>> struct nfs_direct_req *pg_dreq; > > > > >>>> +#ifdef CONFIG_NFS_FSCACHE > > > > >>>> + void *pg_netfs; > > > > >>>> +#endif > > > > >>>> > > > > >>>> @@ -1619,6 +1619,9 @@ struct nfs_pgio_header { > > > > >>>> const struct nfs_rw_ops *rw_ops; > > > > >>>> struct nfs_io_completion *io_completion; > > > > >>>> struct nfs_direct_req *dreq; > > > > >>>> +#ifdef CONFIG_NFS_FSCACHE > > > > >>>> + void *netfs; > > > > >>>> +#endif > > > > >>>> > > > > >>>> > > > > >>>> And these additions to pagelist.c? > > > > >>>> > > > > >>>> @@ -68,6 +69,10 @@ void nfs_pgheader_init(struct > > > > >>>> nfs_pageio_descriptor *desc, > > > > >>>> hdr->good_bytes = mirror->pg_count; > > > > >>>> hdr->io_completion = desc->pg_io_completion; > > > > >>>> hdr->dreq = desc->pg_dreq; > > > > >>>> +#ifdef CONFIG_NFS_FSCACHE > > > > >>>> + if (desc->pg_netfs) > > > > >>>> + hdr->netfs = desc->pg_netfs; > > > > >>>> +#endif > > > > >>> > > > > >>> Why the conditional? > > > > >>> > > > > >> Not really needed and I was thinking of removing it, so I'll do that. > > > > >> > > > > >>>> > > > > >>>> > > > > >>>> @@ -846,6 +851,9 @@ void nfs_pageio_init(struct > > > > >>>> nfs_pageio_descriptor > > > > >>>> *desc, > > > > >>>> desc->pg_lseg = NULL; > > > > >>>> desc->pg_io_completion = NULL; > > > > >>>> desc->pg_dreq = NULL; > > > > >>>> +#ifdef CONFIG_NFS_FSCACHE > > > > >>>> + desc->pg_netfs = NULL; > > > > >>>> +#endif > > > > >>>> > > > > >>>> > > > > >>>> @@ -1360,6 +1369,9 @@ int nfs_pageio_resend(struct > > > > >>>> nfs_pageio_descriptor *desc, > > > > >>>> > > > > >>>> desc->pg_io_completion = hdr->io_completion; > > > > >>>> desc->pg_dreq = hdr->dreq; > > > > >>>> +#ifdef CONFIG_NFS_FSCACHE > > > > >>>> + desc->pg_netfs = hdr->netfs; > > > > >>>> +#endif > > > > >>> > > > > >>> Those all need wrapper functions instead of embedding #ifdefs. > > > > >>> > > > > >> Ok. > > > > >> > > > > >> > > > > >> > > > > >>>> > > > > >>>> > > > > >>>>> My expectation is that the standard I/O path should have minimal > > > > >>>>> overhead, and should certainly not increase the overhead that we > > > > >>>>> already have. Will this be addressed in future iterations of these > > > > >>>>> patches? > > > > >>>>> > > > > >>>> > > > > >>>> I will do what I can to satisfy what you want, either by fixing up > > > > >>>> this patch or follow-on patches. Hopefully the above questions > > > > >>>> will clarify the next steps. > > > > >>>> > > > > >>> > > > > >>> -- > > > > >>> Trond Myklebust > > > > >>> Linux NFS client maintainer, Hammerspace > > > > >>> trond.mykleb...@hammerspace.com > > > > > > > > > > > > > > > > Trond Myklebust > > > > CTO, Hammerspace Inc > > > > 1900 S Norfolk St, Suite 350 - #45 > > > > San Mateo, CA 94403 > > > > > > > > www.hammer.space > > > > > > > > > > > > > > -- Linux-cachefs mailing list Linux-cachefs@redhat.com https://listman.redhat.com/mailman/listinfo/linux-cachefs
