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[88.114.211.119]) by smtp.gmail.com with ESMTPSA id m22sm4560201lji.75.2020.04.25.05.34.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 25 Apr 2020 05:34:03 -0700 (PDT) To: hughd@google.com, linux-mm@kvack.org From: Topi Miettinen Subject: Tmpfs size accounting misses memory allocations Message-ID: <63ab63bd-d6c6-a96a-9667-bbe8edb7cedb@gmail.com> Date: Sat, 25 Apr 2020 15:33:54 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi, It seems that tmpfs does not count memory which is allocated for short symlinks or xattrs towards size= limit. I guess the fix would be to change shmem_sb_info->{used_blocks,max_blocks} to use bytes as units (instead of blocks) and then add accounting and checks to shmem_symlink() and shmem_initxattrs(). Would a patch for that be acceptable? Another issue is that inodes aren't counted towards size= limit either, but perhaps that's intentional because there's nr_inodes= mount option for exactly that. If these are not bugs but intentional features, I think the manual page tmpfs(5) should be clearer in this respect. -Topi