scalloc doesn't clear the buffer

[vincentkfu]

smalloc.c:scalloc() is defined in this way:

void *scalloc(size_t nmemb, size_t size)
{
        return smalloc(nmemb * size);
}

void *smalloc(size_t size)
{
        unsigned int i, end_pool;

        if (size != (unsigned int) size)
                return NULL;

        i = last_pool;
        end_pool = nr_pools;

        do {
                for (; i < end_pool; i++) {
                        void *ptr = smalloc_pool(&mp[i], size);

                        if (ptr) {
                                last_pool = i;
                                return ptr;
                        }
                }
                if (last_pool) {
                        end_pool = last_pool;
                        last_pool = i = 0;
                        continue;
                }

                break;
        } while (1);

        log_err("smalloc: OOM. Consider using --alloc-size to increase the "
                "shared memory available.\n");
        smalloc_debug(size);
        return NULL;
}

scalloc() does not actually clear the buffer returned to the caller. I know of no reports of this actually causing problems but we should fix this.

[axboe]

IIRC, smalloc() used to always clear the allocated region, which is why scalloc() didn't do anything outside of that. Either my memory is wrong, or it just got lost down the line.

I think it was this:

commit 9c3e13e3314da394698ca32f21cc46d46b7cfe47
Author: Jens Axboe <axboe@fb.com>
Date:   Sat Nov 7 17:33:38 2015 -0700

    smalloc: only clear the bitmap, not the whole pool

[axboe]

Just add the memset() to calloc on successful alloc?

Edit: heh, I think you can just do:

$ git revert a640ed36829f3be6d9dd8c7974dba41b9b59e6a5

and be done with it.

[vincentkfu]

Reverted. Thanks for the history!

[vincentkfu]

This turned out not to be a bug:

https://git.kernel.dk/cgit/fio/commit/?id=f956fed4d181d41a5b1c49bba9dce46d8197d428

[axboe]

Should probably have a comment in there, since we've now done it, reverted it, and reverted the revert.

[vincentkfu]

Done: https://git.kernel.dk/cgit/fio/commit/?id=bd7492a47a5bb0ec66a05ae0cff0c9065afb0f88