Could I get any comments?
Unfortunately I do not have enough experience with dlm and cannot verify the
patch locally
Usually you can observe following related problems:
- read after lseek beyond end of file, described by NeilBrown in
commit 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code and
interface")
"dd if=<AFFECTED_FILE> bs=1000 skip=1" will incorrectly generate whole last
line
- read after lseek on into middle of last line will output expected rest of
last line but then repeat whole last line once again.
- If .show() function generates multi-line output following bash script will
never finish.
$ q=;while read -r r;do echo "$((++q)) $r";done < AFFECTED_FILE
Thank you,
Vasily Averin
On 1/24/20 9:03 AM, Vasily Averin wrote:
> if seq_file .next fuction does not change position index,
> read after some lseek can generate unexpected output.
>
> https://bugzilla.kernel.org/show_bug.cgi?id=206283
> Signed-off-by: Vasily Averin <[email protected]>
> ---
> fs/dlm/debug_fs.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/dlm/debug_fs.c b/fs/dlm/debug_fs.c
> index d6bbccb..c1eda93 100644
> --- a/fs/dlm/debug_fs.c
> +++ b/fs/dlm/debug_fs.c
> @@ -523,7 +523,7 @@ static void *table_seq_next(struct seq_file *seq, void
> *iter_ptr, loff_t *pos)
> ri->rsb = r;
> spin_unlock(&ls->ls_rsbtbl[bucket].lock);
> dlm_put_rsb(rp);
> - ++*pos;
> + ++(*pos);
> return ri;
> }
> spin_unlock(&ls->ls_rsbtbl[bucket].lock);
> @@ -542,6 +542,7 @@ static void *table_seq_next(struct seq_file *seq, void
> *iter_ptr, loff_t *pos)
>
> if (bucket >= ls->ls_rsbtbl_size) {
> kfree(ri);
> + ++(*pos);
> return NULL;
> }
> tree = toss ? &ls->ls_rsbtbl[bucket].toss :
> &ls->ls_rsbtbl[bucket].keep;
>
