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By traversing /proc/*/fd and /proc/*/map_files, processes with CAP_ADMIN can get a lot of fine-grained data about how shmem buffers are shared among processes. stat(2) on each entry gives the caller a unique ID (st_ino), the buffer's size (st_size), and even the number of pages currently charged to the buffer (st_blocks / 512). In contrast, all dma-bufs share the same anonymous inode. So while we can count how many dma-buf fds or mappings a process has, we can't get the size of the backing buffers or tell if two entries point to the same dma-buf. On systems with debugfs, we can get a per-buffer breakdown of size and reference count, but can't tell which processes are actually holding the references to each buffer. Replace the singleton inode with full-fledged inodes allocated by alloc_anon_inode(). This involves creating and mounting a mini-pseudo-filesystem for dma-buf, following the example in fs/aio.c. Signed-off-by: Greg Hackmann <ghackmann@google.com> Signed-off-by: Chenbo Feng <fengc@google.com> Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org> Link: https://patchwork.freedesktop.org/patch/msgid/20190613223408.139221-2-fengc@google.com |
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