Hello, here's a set of patches that implement user space notification of file system run-rim errors through sysfs/uevents. The first approach was discussed here: http://marc.info/?t=124404183600003&r=1&w=2 Reasons behind the feature are summarized here: http://marc.info/?l=linux-kernel&m=124409549418926&w=2 Hand-held device with large (large => lengthy/expensive fsck process) FAT volumes on MMC that are error prone, especially in the scenario when these volumes are exported through g_file_storage as USB mass storage to be used externally; instead of just remounting read-only on 'run-rime' error, notify user space and expect it to do something about fixing the FS. Implementation summary: - add sysfs support for FAT fs: per-mounted-volume kobject and sysfs hierarchy under /sys/fs/fat. Same approach as used by ext4 and fuse. (PATCH 1) - introduce kobject attribute 'fs_fault' (/sys/fs/fat/<volume>/fs_fault); the attribute is '0' on (re)mount and set to '1' upon an error. (PATCH 3) FAT error reporting facilities had to be re-factored (PATCH 2) in order to simplify sending error notifications. (PATCH 2) - provide mechanism to optionally notify userspace of FAT fs volume kobject's attribute changes with uevents. An uevent to be sent is of tyme KOBJ_CHANGE, with environment variable 'NAME=value', where NAME is capitalized name of the attribute. (PATCH 4) - add mount option 'notify', which will eneble sending uevents on a FAT kobjects attributes; use it for 'fs_faults' attribute. (PATCH 5) There were several objections to uevent usage, mostly with argument that uevents are meant to be used within a device context. One might argue that uevents are tied to kobjects that are not only used to represent devices, but also for other things (/sys/modules, /sys/fs, /sys/firmware). What is wrong with using uevents otherwise? What would be another way to asyncronousely notify userspace of things happening in kernel, other than though pseudo filesystem files (procfs, sysfs)? Denis -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
