Re: [PATCH] erofs: update ctx->pos for every emitted dirent

[Chao Yu]

On 2022/5/27 15:25, Hongnan Li wrote:

erofs_readdir update ctx->pos after filling a batch of dentries
and it may cause dir/files duplication for NFS readdirplus which
depends on ctx->pos to fill dir correctly. So update ctx->pos for
every emitted dirent in erofs_fill_dentries to fix it.

Fixes: 3e917cc305c6 ("erofs: make filesystem exportable")
Signed-off-by: Hongnan Li <hongnan...@linux.alibaba.com>
---
  fs/erofs/dir.c | 13 ++++++-------
  1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/fs/erofs/dir.c b/fs/erofs/dir.c
index 18e59821c597..3015974fe2ff 100644
--- a/fs/erofs/dir.c
+++ b/fs/erofs/dir.c
@@ -22,11 +22,12 @@ static void debug_one_dentry(unsigned char d_type, const 
char *de_name,
  }

static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,

-                              void *dentry_blk, unsigned int *ofs,
+                              void *dentry_blk, void *dentry_begin,
                               unsigned int nameoff, unsigned int maxsize)
  {
-       struct erofs_dirent *de = dentry_blk + *ofs;
+       struct erofs_dirent *de = dentry_begin;
        const struct erofs_dirent *end = dentry_blk + nameoff;
+       loff_t begin_pos = ctx->pos;

while (de < end) {

                const char *de_name;
@@ -59,9 +60,9 @@ static int erofs_fill_dentries(struct inode *dir, struct 
dir_context *ctx,
                        /* stopped by some reason */
                        return 1;
                ++de;
-               *ofs += sizeof(struct erofs_dirent);
+               ctx->pos += sizeof(struct erofs_dirent);
        }
-       *ofs = maxsize;
+       ctx->pos = begin_pos + maxsize;
        return 0;
  }

@@ -110,11 +111,9 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)

                                goto skip_this;
                }

- err = erofs_fill_dentries(dir, ctx, de, &ofs,

+               err = erofs_fill_dentries(dir, ctx, de, de + ofs,
                                          nameoff, maxsize);
  skip_this:

I guess there are two paths may be affected in erofs_readdir():
- for EFSCORRUPTED case, how about avoiding "goto skip_this" since we
can just break there.
- for initial case, do we need to update ctx->pos as well?

Thanks,

-               ctx->pos = blknr_to_addr(i) + ofs;
-
                if (err)
                        break;
                ++i;