• Sergey SENOZHATSKY's avatar
    zram: keep the exact overcommited value in mem_used_max · 12372755
    Sergey SENOZHATSKY authored
    `mem_used_max' is designed to store the max amount of memory zram consumed
    to store the data.  However, it does not represent the actual
    'overcommited' (max) value.  The existing code goes to -ENOMEM
    overcommited case before it updates `->stats.max_used_pages', which hides
    the reason we went to -ENOMEM in the first place -- we actually used more
    memory than `->limit_pages':
    
            alloced_pages = zs_get_total_pages(meta->mem_pool);
            if (zram->limit_pages && alloced_pages > zram->limit_pages) {
                    zs_free(meta->mem_pool, handle);
                    ret = -ENOMEM;
                    goto out;
            }
    
            update_used_max(zram, alloced_pages);
    
    Which is misleading.  User will see -ENOMEM, check `->limit_pages', check
    `->stats.max_used_pages', which will keep the value BEFORE zram passed
    `->limit_pages', and see:
    	`->stats.max_used_pages' < `->limit_pages'
    
    Move update_used_max() before we do `->limit_pages' check, so that
    user will see:
    	`->stats.max_used_pages' > `->limit_pages'
    should the overcommit and -ENOMEM happen.
    Signed-off-by: default avatarSergey Senozhatsky <sergey.senozhatsky@gmail.com>
    Acked-by: default avatarMinchan Kim <minchan@kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    12372755
zram_drv.c 33.9 KB