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). 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. 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. 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). Thanks, Ben Kind Regards Benjamin Maynard Customer Engineer benmaynard@xxxxxxxxxx Google, Inc. On Mon, 31 Oct 2022 at 22:22, Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> wrote: > > > > > On Oct 30, 2022, at 19:25, David Wysochanski <dwysocha@xxxxxxxxxx> wrote: > > > > On Sat, Oct 29, 2022 at 12:46 PM David Wysochanski <dwysocha@xxxxxxxxxx> wrote: > >> > >> On Fri, Oct 28, 2022 at 12:59 PM Trond Myklebust <trondmy@xxxxxxxxxx> wrote: > >>> > >>> On Fri, 2022-10-28 at 07:50 -0400, David Wysochanski wrote: > >>>> On Thu, Oct 27, 2022 at 3:16 PM Trond Myklebust <trondmy@xxxxxxxxxx> > >>>> 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 <dwysocha@xxxxxxxxxx> > >>>>>> Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx> > >>>>> > >>>>> > >>>>> 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.myklebust@xxxxxxxxxxxxxxx > > > > Trond Myklebust > CTO, Hammerspace Inc > 1900 S Norfolk St, Suite 350 - #45 > San Mateo, CA 94403 > > www.hammer.space > >
