On 2019/11/22 3:53, Hugh Dickins wrote: > On Thu, 21 Nov 2019, zhengbin (A) wrote: >> On 2019/11/21 12:52, Hugh Dickins wrote: >>> Just a rushed FYI without looking at your patch or comments. >>> >>> Internally (in Google) we do rely on good tmpfs inode numbers more >>> than on those of other get_next_ino() filesystems, and carry a patch >>> to mm/shmem.c for it to use 64-bit inode numbers (and separate inode >>> number space for each superblock) - essentially, >>> >>> ino = sbinfo->next_ino++; >>> /* Avoid 0 in the low 32 bits: might appear deleted */ >>> if (unlikely((unsigned int)ino == 0)) >>> ino = sbinfo->next_ino++; >>> >>> Which I think would be faster, and need less memory, than IDA. >>> But whether that is of general interest, or of interest to you, >>> depends upon how prevalent 32-bit executables built without >>> __FILE_OFFSET_BITS=64 still are these days. >> So how google think about this? inode number > 32-bit, but 32-bit executables >> cat not handle this? > Google is free to limit what executables are run on its machines, > and how they are built, so little problem here. > > A general-purpose 32-bit Linux distribution does not have that freedom, > does not want to limit what the user runs. But I thought that by now > they (and all serious users of 32-bit systems) were building their own > executables with _FILE_OFFSET_BITS=64 (I was too generous with the > underscores yesterday); and I thought that defined __USE_FILE_OFFSET64, > and that typedef'd ino_t to be __ino64_t. And the 32-bit kernel would > have __ARCH_WANT_STAT64, which delivers st_ino as unsigned long long. > > So I thought that a modern, professional 32-bit executable would be > dealing in 64-bit inode numbers anyway. But I am not a system builder, > so perhaps I'm being naive. And of course some users may have to support > some old userspace, or apps that assign inode numbers to "int" or "long" > or whatever. I have no insight into the extent of that problem. So how to solve this problem? 1. tmpfs use ida or other data structure 2. tmpfs use 64-bit, each superblock a inode number space 3. do not do anything, If somebody hits this bug, let them solve for themselves 4. (last_ino change to 64-bit)get_next_ino -->other filesystems will be ok, but it was rejected before > > Hugh > > . >
