When provisioning containerized applications, multiple very small tmpfs are used, for which one cannot always predict the proper file system size ahead of time. We want to be able to reliably monitor filesystems for ENOSPC errors, without depending on the application being executed reporting the ENOSPC after a failure. It is also not enough to watch statfs since that information might be ephemeral (say the application recovers by deleting data, the issue can get lost). For this use case, it is also interesting to differentiate IO errors caused by lack of virtual memory from lack of FS space. This patch exposes two counters on sysfs that log the two conditions that are interesting to observe for container provisioning. They are recorded per tmpfs superblock, and can be polled by a monitoring application. I proposed a more general approach [1] using fsnotify, but considering the specificity of this use-case, people agreed it seems that a simpler solution in sysfs is more than enough. [1] https://lore.kernel.org/linux-mm/20211116220742.584975-3-krisman@xxxxxxxxxxxxx/T/#mee338d25b0e1e07cbe0861f9a5ca8cc439b3edb8 Gabriel Krisman Bertazi (3): shmem: Keep track of out-of-memory and out-of-space errors shmem: Introduce /sys/fs/tmpfs support shmem: Expose space and accounting error count Documentation/ABI/testing/sysfs-fs-tmpfs | 13 +++ include/linux/shmem_fs.h | 7 ++ mm/shmem.c | 103 ++++++++++++++++++++++- 3 files changed, 121 insertions(+), 2 deletions(-) create mode 100644 Documentation/ABI/testing/sysfs-fs-tmpfs -- 2.35.1
