The various mount options, tunables, proc files, etc in ext4 are largely undocumented.
Could you re-evaluate this bug? There are some documentation update in latest kernel 2.6.26, please check Documentation/filesystems/ext4.txt and Documentation/filesystems/proc.txt to see if there is something we should add. I think we are okay now... Thanks.
Well, let's see. For the proc files, technically they are documented in proc.txt (though I'd probably rather move them to filesystems/ext4.txt?) But, they could use some work; for example these are not very clear: order2_req: Multiblock allocator use 2^N search using buddies only for requests greater than or equal to order2_req. The request size is specfied in file system blocks. A value of 2 indicate only if the requests are greater than or equal to 4 blocks. stream_req: Files smaller than stream_req are served by the stream allocator, whose purpose is to pack requests as close each to other as possible to produce smooth I/O traffic. Avalue of 16 indicate that file smaller than 16 filesystem block size will use group based preallocation. I can see if I can do some editing either for clarity or grammar/spelling ... from fs/ext4/super.c, we're now up to 57 mount options: abort delalloc journal_dev=%u nogrpid resize acl errors=continue journal=%u noload resuid=%u barrier=%u errors=panic journal=update nomballoc sb=%u bh errors=remount-ro jqfmt=vfsold noquota stripe=%u bsddf extents jqfmt=vfsv0 noreservation sysvgroups bsdgroups grpid mballoc nouid32 user_xattr check=none grpjquota= minixdf nouser_xattr usrjquota= commit=%u grpjquota=%s noacl oldalloc usrjquota=%s data=journal grpquota nobh orlov usrquota data=ordered i_version nocheck quota data=writeback journal_async_commit nodelalloc reservation debug journal_checksum noextents resgid=%u ... most of these actually are documented, but not these: nouid32 not found abort not found usrjquota not found usrjquota not found grpjquota not found grpjquota not found jqfmt not found jqfmt not found i_version not found resize not found for ioctls, I suppose EXT4_IOC_MIGRATE is the only new one, but I'm not certain if any of them are documented anywhere? -Eric
Patch added to ext4 patch queue to fix/update documentation.