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Sun, 16 Nov 2025 19:53:02 +0800 Message-ID: Date: Sun, 16 Nov 2025 19:53:01 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 1/9] iomap: stash iomap read ctx in the private field of iomap_iter To: Hongbo Li , chao@kernel.org, brauner@kernel.org, djwong@kernel.org, amir73il@gmail.com, joannelkoong@gmail.com Cc: linux-fsdevel@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-kernel@vger.kernel.org References: <20251114095516.207555-1-lihongbo22@huawei.com> <20251114095516.207555-2-lihongbo22@huawei.com> From: Gao Xiang In-Reply-To: <20251114095516.207555-2-lihongbo22@huawei.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2025/11/14 17:55, Hongbo Li wrote: > It's useful to get filesystem-specific information using the > existing private field in the @iomap_iter passed to iomap_{begin,end} > for advanced usage for iomap buffered reads, which is much like the > current iomap DIO. > > For example, EROFS needs it to: > > - implement an efficient page cache sharing feature, since iomap > needs to apply to anon inode page cache but we'd like to get the > backing inode/fs instead, so filesystem-specific private data is > needed to keep such information; > > - pass in both struct page * and void * for inline data to avoid > kmap_to_page() usage (which is bogus). > > Signed-off-by: Hongbo Li > --- > fs/fuse/file.c | 4 ++-- > fs/iomap/buffered-io.c | 6 ++++-- > include/linux/iomap.h | 8 ++++---- > 3 files changed, 10 insertions(+), 8 deletions(-) > > diff --git a/fs/fuse/file.c b/fs/fuse/file.c > index 8275b6681b9b..98dd20f0bb53 100644 > --- a/fs/fuse/file.c > +++ b/fs/fuse/file.c > @@ -973,7 +973,7 @@ static int fuse_read_folio(struct file *file, struct folio *folio) > return -EIO; > } > > - iomap_read_folio(&fuse_iomap_ops, &ctx); > + iomap_read_folio(&fuse_iomap_ops, &ctx, NULL); > fuse_invalidate_atime(inode); > return 0; > } > @@ -1075,7 +1075,7 @@ static void fuse_readahead(struct readahead_control *rac) > if (fuse_is_bad(inode)) > return; > > - iomap_readahead(&fuse_iomap_ops, &ctx); > + iomap_readahead(&fuse_iomap_ops, &ctx, NULL); > } > > static ssize_t fuse_cache_read_iter(struct kiocb *iocb, struct iov_iter *to) > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index 6ae031ac8058..8e79303c074e 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -496,13 +496,14 @@ static int iomap_read_folio_iter(struct iomap_iter *iter, > } > > void iomap_read_folio(const struct iomap_ops *ops, > - struct iomap_read_folio_ctx *ctx) > + struct iomap_read_folio_ctx *ctx, void *private) > { > struct folio *folio = ctx->cur_folio; > struct iomap_iter iter = { > .inode = folio->mapping->host, > .pos = folio_pos(folio), > .len = folio_size(folio), > + .private = private, > }; > size_t bytes_pending = 0; > int ret; > @@ -560,13 +561,14 @@ static int iomap_readahead_iter(struct iomap_iter *iter, > * the filesystem to be reentered. > */ > void iomap_readahead(const struct iomap_ops *ops, > - struct iomap_read_folio_ctx *ctx) > + struct iomap_read_folio_ctx *ctx, void *private) > { > struct readahead_control *rac = ctx->rac; > struct iomap_iter iter = { > .inode = rac->mapping->host, > .pos = readahead_pos(rac), > .len = readahead_length(rac), > + .private = private, > }; > size_t cur_bytes_pending; > > diff --git a/include/linux/iomap.h b/include/linux/iomap.h > index 8b1ac08c7474..c3ecbbdb14e8 100644 > --- a/include/linux/iomap.h > +++ b/include/linux/iomap.h > @@ -341,9 +341,9 @@ ssize_t iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *from, > const struct iomap_ops *ops, > const struct iomap_write_ops *write_ops, void *private); > void iomap_read_folio(const struct iomap_ops *ops, > - struct iomap_read_folio_ctx *ctx); > + struct iomap_read_folio_ctx *ctx, void *private); > void iomap_readahead(const struct iomap_ops *ops, > - struct iomap_read_folio_ctx *ctx); > + struct iomap_read_folio_ctx *ctx, void *private); > bool iomap_is_partially_uptodate(struct folio *, size_t from, size_t count); > struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos, size_t len); > bool iomap_release_folio(struct folio *folio, gfp_t gfp_flags); > @@ -594,7 +594,7 @@ static inline void iomap_bio_read_folio(struct folio *folio, > .cur_folio = folio, > }; > > - iomap_read_folio(ops, &ctx); > + iomap_read_folio(ops, &ctx, NULL); > } > > static inline void iomap_bio_readahead(struct readahead_control *rac, > @@ -605,7 +605,7 @@ static inline void iomap_bio_readahead(struct readahead_control *rac, > .rac = rac, > }; > > - iomap_readahead(ops, &ctx); > + iomap_readahead(ops, &ctx, NULL); > } > #endif /* CONFIG_BLOCK */ >