Re: [PATCH] ceph: improve error handling and short/overflow-read logic in __ceph_sync_read()

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On Sun, 2024-12-08 at 17:32 +0000, Alex Markuze wrote:
> This patch refines the read logic in __ceph_sync_read() to ensure
> more
> predictable and efficient behavior in various edge cases.
> 
> - Return early if the requested read length is zero or if the file
> size
>   (`i_size`) is zero.
> - Initialize the index variable (`idx`) where needed and reorder some
>   code to ensure it is always set before use.
> - Improve error handling by checking for negative return values
> earlier.
> - Remove redundant encrypted file checks after failures. Only attempt
>   filesystem-level decryption if the read succeeded.
> - Simplify leftover calculations to correctly handle cases where the
> read
>   extends beyond the end of the file or stops short.
> - This resolves multiple issues caused by integer overflow
>   -
> https://tracker.ceph.com/issues/67524 
>  
>   -
> https://tracker.ceph.com/issues/68981 
>  
>   -
> https://tracker.ceph.com/issues/68980 
>  
> 
> Signed-off-by: Alex Markuze <amarkuze@xxxxxxxxxx>
> ---
>  fs/ceph/file.c | 29 ++++++++++++++---------------
>  1 file changed, 14 insertions(+), 15 deletions(-)
> 
> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> index ce342a5d4b8b..8e0400d461a2 100644
> --- a/fs/ceph/file.c
> +++ b/fs/ceph/file.c
> @@ -1066,7 +1066,7 @@ ssize_t __ceph_sync_read(struct inode *inode,
> loff_t *ki_pos,
>          if (ceph_inode_is_shutdown(inode))
>                  return -EIO;
>  
> -       if (!len)
> +       if (!len || !i_size)
>                  return 0;
>          /*
>           * flush any page cache pages in this range.  this
> @@ -1086,7 +1086,7 @@ ssize_t __ceph_sync_read(struct inode *inode,
> loff_t *ki_pos,
>                  int num_pages;
>                  size_t page_off;
>                  bool more;
> -               int idx;
> +               int idx = 0;
>                  size_t left;
>                  struct ceph_osd_req_op *op;
>                  u64 read_off = off;
> @@ -1160,7 +1160,14 @@ ssize_t __ceph_sync_read(struct inode *inode,
> loff_t *ki_pos,
>                  else if (ret == -ENOENT)
>                          ret = 0;
>  
> -               if (ret > 0 && IS_ENCRYPTED(inode)) {
> +               if (ret < 0) {

If I understood correctly, you simply added the check for error in the
execution flow (ret < 0) before processing IS_ENCRYPTED(inode)
condition. Am I correct here?

Thanks,
Slava.

> +                       ceph_osdc_put_request(req);
> +                       if (ret == -EBLOCKLISTED)
> +                               fsc->blocklisted = true;
> +                       break;
> +               }
> +
> +               if (IS_ENCRYPTED(inode)) {
>                          int fret;
>  
>                          fret = ceph_fscrypt_decrypt_extents(inode,
> pages,
> @@ -1187,7 +1194,7 @@ ssize_t __ceph_sync_read(struct inode *inode,
> loff_t *ki_pos,
>                  }
>  
>                  /* Short read but not EOF? Zero out the remainder.
> */
> -               if (ret >= 0 && ret < len && (off + ret < i_size)) {
> +               if (ret < len && (off + ret < i_size)) {
>                          int zlen = min(len - ret, i_size - off -
> ret);
>                          int zoff = page_off + ret;
>  
> @@ -1197,13 +1204,11 @@ ssize_t __ceph_sync_read(struct inode *inode,
> loff_t *ki_pos,
>                          ret += zlen;
>                  }
>  
> -               idx = 0;
> -               if (ret <= 0)
> -                       left = 0;
> -               else if (off + ret > i_size)
> -                       left = i_size - off;
> +               if (off + ret > i_size)
> +                       left = (i_size > off) ? i_size - off : 0;
>                  else
>                          left = ret;
> +
>                  while (left > 0) {
>                          size_t plen, copied;
>  
> @@ -1222,12 +1227,6 @@ ssize_t __ceph_sync_read(struct inode *inode,
> loff_t *ki_pos,
>  
>                  ceph_osdc_put_request(req);
>  
> -               if (ret < 0) {
> -                       if (ret == -EBLOCKLISTED)
> -                               fsc->blocklisted = true;
> -                       break;
> -               }
> -
>                  if (off >= i_size || !more)
>                          break;
>          }
> --
> 2.34.1






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