iolog, dataplacement: fix coverity scan defect

[parkvibes]

iolog: fix Error handling issues (NEGATIVE_RETURNS)

CID 494151: Error handling issues (NEGATIVE_RETURNS) @ io_u.c:1877 in get_io_u()
This patch removes negative returns from dp_init() to ensure
its value can be properly consumed by td_verror()

Signed-off-by: Hyunwoo Park [email protected]

iolog: fix Null pointer dereferences (FORWARD_NULL)

CID 494150: Null pointer dereferences (FORWARD_NULL) @ iolog.c:148 in ipo_special()
This patch removes the possibility of null pointer dereferencing(io_u->file)
throughout the call stack of get_io_u() → read_iolog_get() → dp_fill_dspec_data()

Signed-off-by: Hyunwoo Park [email protected]

[vincentkfu]

Please change the first lines of the commit messages to describe the actual issue instead of just writing that the issue was identified by coverity.

[vincentkfu]

For the negative errno issue I would much rather see code that does something like what zbd.c:zbd_init_zone_info() does:

        ret = zbd_create_zone_info(td, file);
        if (ret < 0)
                td_verror(td, -ret, "zbd_create_zone_info() failed");

Just negate the value sent to td_verror(). This involves fewer code changes than your patch.

I do not know the full history of returning negative errno values but this is a common pattern: https://stackoverflow.com/questions/36845866/history-of-using-negative-errno-values-in-gnu

[parkvibes]

As dp_init() can return a positive value, I made dp_init_ret an absolute value using abs(dp_init_ret) instead of -dp_init_ret