From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 20BB83E462; Thu, 14 Dec 2023 14:07:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="IuU+Ti7I" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CAFCDC433C7; Thu, 14 Dec 2023 14:07:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1702562851; bh=9BLM+8qwcvl/5vM2uEaRxfm58T5UnEeUHi1BK0de4ak=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=IuU+Ti7Ig9BEHGWxIBw1DJbtactT68k/HlsJToI2vUeWq9EJ1U2mT0k1T5D2xujoM B1rYB5j5idW2FL5RHh8SVSgwbWkEua6byHbIh5zCcVmxRmMP51w2PBl2derU/6yO0z ssQwz8+KBEPWwMTGOW4dPXut1/X1lToKBU5F8OXTR9SELjzy/VkeavIZv8OnJNh4o8 0rK+lP6rYfi+n5z+t0sJRKcdQ43Ia0R/QlaHc3UTt1U6oOH4rkiZpMFkoxHO7yHVXo /rR4D5gZfcBIl3UiwfXtNkJX80NncEVj3Np/wvQqP70YyjSMV2p9IQgN/h4TangZEz Shx7/M6nv64Qg== Message-ID: <8b9413cc37a231a97059c7d028d404ab35363764.camel@kernel.org> Subject: Re: [PATCH v4 37/39] netfs: Optimise away reads above the point at which there can be no data From: Jeff Layton To: David Howells , Steve French Cc: Matthew Wilcox , Marc Dionne , Paulo Alcantara , Shyam Prasad N , Tom Talpey , Dominique Martinet , Eric Van Hensbergen , Ilya Dryomov , Christian Brauner , linux-cachefs@redhat.com, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 14 Dec 2023 09:07:28 -0500 In-Reply-To: <20231213152350.431591-38-dhowells@redhat.com> References: <20231213152350.431591-1-dhowells@redhat.com> <20231213152350.431591-38-dhowells@redhat.com> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; 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 kZWuOsJdJQdmwlWC5L5ln9xgfr/4mOY38B0U= Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.2 (3.50.2-1.fc39) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2023-12-13 at 15:23 +0000, David Howells wrote: > Track the file position above which the server is not expected to have an= y > data (the "zero point") and preemptively assume that we can satisfy > requests by filling them with zeroes locally rather than attempting to > download them if they're over that line - even if we've written data back > to the server. Assume that any data that was written back above that > position is held in the local cache. Note that we have to split requests > that straddle the line. >=20 > Make use of this to optimise away some reads from the server. We need to > set the zero point in the following circumstances: >=20 > (1) When we see an extant remote inode and have no cache for it, we set > the zero_point to i_size. >=20 > (2) On local inode creation, we set zero_point to 0. >=20 > (3) On local truncation down, we reduce zero_point to the new i_size if > the new i_size is lower. >=20 > (4) On local truncation up, we don't change zero_point. >=20 The above seems odd, but I guess the assumption is that if there are any writes by a 3rd party above the old zero point, that that would cause an invalidation? > (5) On local modification, we don't change zero_point. >=20 > (6) On remote invalidation, we set zero_point to the new i_size. >=20 > (7) If stored data is discarded from the pagecache or culled from fscach= e, > we must set zero_point above that if the data also got written to th= e > server. >=20 > (8) If dirty data is written back to the server, but not fscache, we mus= t > set zero_point above that. >=20 > (9) If a direct I/O write is made, set zero_point above that. >=20 > Assuming the above, any read from the server at or above the zero_point > position will return all zeroes. >=20 > The zero_point value can be stored in the cache, provided the above rules > are applied to it by any code that culls part of the local cache. >=20 > Signed-off-by: David Howells > cc: Jeff Layton > cc: linux-cachefs@redhat.com > cc: linux-fsdevel@vger.kernel.org > cc: linux-mm@kvack.org > --- > fs/afs/inode.c | 22 +++++++++++++--------- > fs/netfs/buffered_write.c | 2 +- > fs/netfs/direct_write.c | 4 ++++ > fs/netfs/io.c | 10 ++++++++++ > fs/netfs/misc.c | 5 +++++ > fs/smb/client/cifsfs.c | 4 ++-- > include/linux/netfs.h | 14 ++++++++++++-- > 7 files changed, 47 insertions(+), 14 deletions(-) >=20 > diff --git a/fs/afs/inode.c b/fs/afs/inode.c > index c43112dcbbbb..dfd940a64e0f 100644 > --- a/fs/afs/inode.c > +++ b/fs/afs/inode.c > @@ -166,6 +166,7 @@ static void afs_apply_status(struct afs_operation *op= , > struct inode *inode =3D &vnode->netfs.inode; > struct timespec64 t; > umode_t mode; > + bool unexpected_jump =3D false; > bool data_changed =3D false; > bool change_size =3D vp->set_size; > =20 > @@ -230,6 +231,7 @@ static void afs_apply_status(struct afs_operation *op= , > } > change_size =3D true; > data_changed =3D true; > + unexpected_jump =3D true; > } else if (vnode->status.type =3D=3D AFS_FTYPE_DIR) { > /* Expected directory change is handled elsewhere so > * that we can locally edit the directory and save on a > @@ -251,6 +253,8 @@ static void afs_apply_status(struct afs_operation *op= , > vnode->netfs.remote_i_size =3D status->size; > if (change_size || status->size > i_size_read(inode)) { > afs_set_i_size(vnode, status->size); > + if (unexpected_jump) > + vnode->netfs.zero_point =3D status->size; > inode_set_ctime_to_ts(inode, t); > inode_set_atime_to_ts(inode, t); > } > @@ -689,17 +693,17 @@ static void afs_setattr_success(struct afs_operatio= n *op) > static void afs_setattr_edit_file(struct afs_operation *op) > { > struct afs_vnode_param *vp =3D &op->file[0]; > - struct inode *inode =3D &vp->vnode->netfs.inode; > + struct afs_vnode *vnode =3D vp->vnode; > =20 > if (op->setattr.attr->ia_valid & ATTR_SIZE) { > loff_t size =3D op->setattr.attr->ia_size; > loff_t i_size =3D op->setattr.old_i_size; > =20 > - if (size < i_size) > - truncate_pagecache(inode, size); > - if (size !=3D i_size) > - fscache_resize_cookie(afs_vnode_cache(vp->vnode), > - vp->scb.status.size); > + if (size !=3D i_size) { > + truncate_setsize(&vnode->netfs.inode, size); > + netfs_resize_file(&vnode->netfs, size, true); > + fscache_resize_cookie(afs_vnode_cache(vnode), size); > + } > } > } > =20 > @@ -767,11 +771,11 @@ int afs_setattr(struct mnt_idmap *idmap, struct den= try *dentry, > */ > if (!(attr->ia_valid & (supported & ~ATTR_SIZE & ~ATTR_MTIME)) && > attr->ia_size < i_size && > - attr->ia_size > vnode->status.size) { > - truncate_pagecache(inode, attr->ia_size); > + attr->ia_size > vnode->netfs.remote_i_size) { > + truncate_setsize(inode, attr->ia_size); > + netfs_resize_file(&vnode->netfs, size, false); > fscache_resize_cookie(afs_vnode_cache(vnode), > attr->ia_size); > - i_size_write(inode, attr->ia_size); > ret =3D 0; > goto out_unlock; > } > diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c > index dce6995fb644..d7ce424b9188 100644 > --- a/fs/netfs/buffered_write.c > +++ b/fs/netfs/buffered_write.c > @@ -73,7 +73,7 @@ static enum netfs_how_to_modify netfs_how_to_modify(str= uct netfs_inode *ctx, > if (folio_test_uptodate(folio)) > return NETFS_FOLIO_IS_UPTODATE; > =20 > - if (pos >=3D ctx->remote_i_size) > + if (pos >=3D ctx->zero_point) > return NETFS_MODIFY_AND_CLEAR; > =20 > if (!maybe_trouble && offset =3D=3D 0 && len >=3D flen) > diff --git a/fs/netfs/direct_write.c b/fs/netfs/direct_write.c > index bb0c2718f57b..aad05f2349a4 100644 > --- a/fs/netfs/direct_write.c > +++ b/fs/netfs/direct_write.c > @@ -134,6 +134,7 @@ ssize_t netfs_unbuffered_write_iter(struct kiocb *ioc= b, struct iov_iter *from) > struct file *file =3D iocb->ki_filp; > struct inode *inode =3D file->f_mapping->host; > struct netfs_inode *ictx =3D netfs_inode(inode); > + unsigned long long end; > ssize_t ret; > =20 > _enter("%llx,%zx,%llx", iocb->ki_pos, iov_iter_count(from), i_size_read= (inode)); > @@ -155,6 +156,9 @@ ssize_t netfs_unbuffered_write_iter(struct kiocb *ioc= b, struct iov_iter *from) > ret =3D kiocb_invalidate_pages(iocb, iov_iter_count(from)); > if (ret < 0) > goto out; > + end =3D iocb->ki_pos + iov_iter_count(from); > + if (end > ictx->zero_point) > + ictx->zero_point =3D end; > =20 > fscache_invalidate(netfs_i_cookie(ictx), NULL, i_size_read(inode), > FSCACHE_INVAL_DIO_WRITE); > diff --git a/fs/netfs/io.c b/fs/netfs/io.c > index 5d9098db815a..41a6113aa7fa 100644 > --- a/fs/netfs/io.c > +++ b/fs/netfs/io.c > @@ -569,6 +569,7 @@ netfs_rreq_prepare_read(struct netfs_io_request *rreq= , > struct iov_iter *io_iter) > { > enum netfs_io_source source =3D NETFS_DOWNLOAD_FROM_SERVER; > + struct netfs_inode *ictx =3D netfs_inode(rreq->inode); > size_t lsize; > =20 > _enter("%llx-%llx,%llx", subreq->start, subreq->start + subreq->len, rr= eq->i_size); > @@ -586,6 +587,14 @@ netfs_rreq_prepare_read(struct netfs_io_request *rre= q, > * to make serial calls, it can indicate a short read and then > * we will call it again. > */ > + if (rreq->origin !=3D NETFS_DIO_READ) { > + if (subreq->start >=3D ictx->zero_point) { > + source =3D NETFS_FILL_WITH_ZEROES; > + goto set; > + } > + if (subreq->len > ictx->zero_point - subreq->start) > + subreq->len =3D ictx->zero_point - subreq->start; > + } > if (subreq->len > rreq->i_size - subreq->start) > subreq->len =3D rreq->i_size - subreq->start; > if (rreq->rsize && subreq->len > rreq->rsize) > @@ -607,6 +616,7 @@ netfs_rreq_prepare_read(struct netfs_io_request *rreq= , > } > } > =20 > +set: > if (subreq->len > rreq->len) > pr_warn("R=3D%08x[%u] SREQ>RREQ %zx > %zx\n", > rreq->debug_id, subreq->debug_index, > diff --git a/fs/netfs/misc.c b/fs/netfs/misc.c > index 40421ced4cd3..31e45dfad5b0 100644 > --- a/fs/netfs/misc.c > +++ b/fs/netfs/misc.c > @@ -240,6 +240,11 @@ EXPORT_SYMBOL(netfs_invalidate_folio); > bool netfs_release_folio(struct folio *folio, gfp_t gfp) > { > struct netfs_inode *ctx =3D netfs_inode(folio_inode(folio)); > + unsigned long long end; > + > + end =3D folio_pos(folio) + folio_size(folio); > + if (end > ctx->zero_point) > + ctx->zero_point =3D end; > =20 > if (folio_test_private(folio)) > return false; > diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c > index 96a65cf9b5ec..07cd88897c33 100644 > --- a/fs/smb/client/cifsfs.c > +++ b/fs/smb/client/cifsfs.c > @@ -1220,7 +1220,7 @@ static int cifs_precopy_set_eof(struct inode *src_i= node, struct cifsInodeInfo *s > if (rc < 0) > goto set_failed; > =20 > - netfs_resize_file(&src_cifsi->netfs, src_end); > + netfs_resize_file(&src_cifsi->netfs, src_end, true); > fscache_resize_cookie(cifs_inode_cookie(src_inode), src_end); > return 0; > =20 > @@ -1351,7 +1351,7 @@ static loff_t cifs_remap_file_range(struct file *sr= c_file, loff_t off, > smb_file_src, smb_file_target, off, len, destoff); > if (rc =3D=3D 0 && new_size > i_size_read(target_inode)) { > truncate_setsize(target_inode, new_size); > - netfs_resize_file(&target_cifsi->netfs, new_size); > + netfs_resize_file(&target_cifsi->netfs, new_size, true); > fscache_resize_cookie(cifs_inode_cookie(target_inode), > new_size); > } > diff --git a/include/linux/netfs.h b/include/linux/netfs.h > index fc77f7be220a..2005ad3b0e25 100644 > --- a/include/linux/netfs.h > +++ b/include/linux/netfs.h > @@ -136,6 +136,8 @@ struct netfs_inode { > struct fscache_cookie *cache; > #endif > loff_t remote_i_size; /* Size of the remote file */ > + loff_t zero_point; /* Size after which we assume there's no data > + * on the server */ > unsigned long flags; > #define NETFS_ICTX_ODIRECT 0 /* The file has DIO in progress */ > #define NETFS_ICTX_UNBUFFERED 1 /* I/O should not use the pagecache */ > @@ -465,22 +467,30 @@ static inline void netfs_inode_init(struct netfs_in= ode *ctx, > { > ctx->ops =3D ops; > ctx->remote_i_size =3D i_size_read(&ctx->inode); > + ctx->zero_point =3D ctx->remote_i_size; > ctx->flags =3D 0; > #if IS_ENABLED(CONFIG_FSCACHE) > ctx->cache =3D NULL; > #endif > + /* ->releasepage() drives zero_point */ > + mapping_set_release_always(ctx->inode.i_mapping); > } > =20 > /** > * netfs_resize_file - Note that a file got resized > * @ctx: The netfs inode being resized > * @new_i_size: The new file size > + * @changed_on_server: The change was applied to the server > * > * Inform the netfs lib that a file got resized so that it can adjust it= s state. > */ > -static inline void netfs_resize_file(struct netfs_inode *ctx, loff_t new= _i_size) > +static inline void netfs_resize_file(struct netfs_inode *ctx, loff_t new= _i_size, > + bool changed_on_server) > { > - ctx->remote_i_size =3D new_i_size; > + if (changed_on_server) > + ctx->remote_i_size =3D new_i_size; > + if (new_i_size < ctx->zero_point) > + ctx->zero_point =3D new_i_size; > } > =20 > /** >=20 --=20 Jeff Layton