iomap: stash iomap read ctx in the private field of iomap_iter

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 <lihongbo22@huawei.com>
Link: https://patch.msgid.link/20260109102856.598531-2-lihongbo22@huawei.com
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 01bc894e9c2baee49a9b8ddb7ab036244e574b37..f5d8887c19229d784c7eca01179df50ca2a09cff 100644 (file)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -979,7 +979,7 @@ 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;
 }
@@ -1081,7 +1081,7 @@ 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 e5c1ca440d93bd7468eb2fbf37760295672622e9..5f7dcbabbda363079a1195a72b281d8840948337 100644 (file)
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -555,13 +555,14 @@ 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_submitted = 0;
        int ret;
@@ -620,13 +621,14 @@ 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_submitted;
 

diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 520e967cb501d335fd8fc9361cbbeba0042a9a4e..441d614e9fdfd2e1efe8dfa5f38ade8dbc25a3f2 100644 (file)
--- 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);
@@ -595,7 +595,7 @@ 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,
@@ -606,7 +606,7 @@ static inline void iomap_bio_readahead(struct readahead_control *rac,
                .rac            = rac,
        };
 
-       iomap_readahead(ops, &ctx);
+       iomap_readahead(ops, &ctx, NULL);
 }
 #endif /* CONFIG_BLOCK */