Re: [PATCH] erofs-utils: add I/O control for tarerofs stream via `erofs_vfile`

[Gao Xiang]

Hi,

On 2024/6/11 15:54, Hongzhen Luo wrote:

This adds I/O control for tarerofs stream.

Signed-off-by: Hongzhen Luo <hongz...@linux.alibaba.com>
---
  include/erofs/io.h  |  1 +
  include/erofs/tar.h |  2 +-
  lib/tar.c           | 16 ++++++++++------
  3 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/include/erofs/io.h b/include/erofs/io.h
index c82dfdf..a501685 100644
--- a/include/erofs/io.h
+++ b/include/erofs/io.h
@@ -26,6 +26,7 @@ struct erofs_vfile;

struct erofs_vfops {

        int (*pread)(struct erofs_vfile *vf, void *buf, u64 offset, size_t len);
+       int (*read)(struct erofs_vfile *vf, void *buf, size_t len);

I think you need to add both read and lseek.

        int (*pwrite)(struct erofs_vfile *vf, const void *buf, u64 offset, 
size_t len);
        int (*fsync)(struct erofs_vfile *vf);
        int (*fallocate)(struct erofs_vfile *vf, u64 offset, size_t len, bool 
pad);
diff --git a/include/erofs/tar.h b/include/erofs/tar.h
index b5c966b..e1de0df 100644
--- a/include/erofs/tar.h
+++ b/include/erofs/tar.h
@@ -39,7 +39,7 @@ struct erofs_iostream_liblzma {

struct erofs_iostream {

        union {
-               int fd;                 /* original fd */
+               struct erofs_vfile vf;
                void *handler;
  #ifdef HAVE_LIBLZMA
                struct erofs_iostream_liblzma *lzma;
diff --git a/lib/tar.c b/lib/tar.c
index 3514381..77e09ae 100644
--- a/lib/tar.c
+++ b/lib/tar.c
@@ -79,7 +79,7 @@ void erofs_iostream_close(struct erofs_iostream *ios)
  #endif
                return;
        }
-       close(ios->fd);
+       close(ios->vf.fd);
  }

int erofs_iostream_open(struct erofs_iostream *ios, int fd, int decoder)

@@ -119,7 +119,7 @@ int erofs_iostream_open(struct erofs_iostream *ios, int fd, 
int decoder)
                return -EOPNOTSUPP;
  #endif
        } else {
-               ios->fd = fd;
+               ios->vf.fd = fd;
                fsz = lseek(fd, 0, SEEK_END);
                if (fsz <= 0) {
                        ios->feof = !fsz;
@@ -218,8 +218,12 @@ int erofs_iostream_read(struct erofs_iostream *ios, void 
**buf, u64 bytes)
                        return -EOPNOTSUPP;
  #endif
                } else {
-                       ret = erofs_read_from_fd(ios->fd, ios->buffer + rabytes,
-                                                ios->bufsize - rabytes);
+                       if (ios->vf.ops)
+                               ret = ios->vf.ops->read(&ios->vf, ios->buffer + 
rabytes,
+                                                        ios->bufsize - 
rabytes);
+                       else
+                               ret = erofs_read_from_fd(ios->vf.fd, 
ios->buffer + rabytes,
+                                                        ios->bufsize - 
rabytes);

I guess this could be moved into lib/io.c? and call erofs_io_read() here.

                        if (ret < 0)
                                return ret;
                        ios->tail += ret;
@@ -270,8 +274,8 @@ int erofs_iostream_lskip(struct erofs_iostream *ios, u64 sz)
        if (ios->feof)
                return sz;

- if (ios->sz && likely(ios->dumpfd < 0)) {

-               s64 cur = lseek(ios->fd, sz, SEEK_CUR);
+       if (ios->sz && likely(ios->dumpfd < 0) && !ios->vf.ops) {
+               s64 cur = lseek(ios->vf.fd, sz, SEEK_CUR);

Same here, erofs_io_lseek is needed.

Thanks,
Gao Xiang