* mount: implement fallocate instead of reporting it unsupported
Fallocate answered ENOSYS, so the kernel marked the mount as having no
fallocate and returned EOPNOTSUPP. glibc then fell back to its emulation,
which preads a byte from every block already inside the file to see if it
is allocated; on a write-only descriptor that pread is EBADF, and
posix_fallocate returned it.
Volume space is assigned when a write is flushed, so nothing can be
reserved up front: a range inside the file is answered OK untouched, and
one past the end grows the file the way a truncate would. A mode we
cannot honor is refused with ENOTSUP, not ENOSYS, so the kernel keeps
sending the ones we do.
Claude-Session: https://claude.ai/code/session_01XG6sAAdkqTwWffqK5h4rH9
* mount: let a fallocate that allocates nothing past the quota and worm guards
A range already inside the file, and any FALLOC_FL_KEEP_SIZE request,
reserve no space and rewrite no entry, but the preflight refused them
with ENOSPC on a full mount and EPERM on a worm-enforced file. Decide
the no-op first and guard only the growth.
Claude-Session: https://claude.ai/code/session_01XG6sAAdkqTwWffqK5h4rH9
* mount: charge a fallocate growth to the uncommitted byte counter
Write charges the counter by how much the file grew, so the writes that
fill a range fallocate already extended charge nothing and the real-time
quota check never sees that data — only the periodic filer refresh does.
Count the growth where it happens.
Claude-Session: https://claude.ai/code/session_01XG6sAAdkqTwWffqK5h4rH9
* mount: charge a truncate-up growth to the uncommitted byte counter
Same gap Fallocate had: Write charges the counter by how much the file
grew, so the writes that fill a range ftruncate already extended charge
nothing and the real-time quota check never sees that data. Count the
growth where it happens; a shrink still leaves the counter alone, since
it is only ever raised and then reset by the periodic filer refresh.
Claude-Session: https://claude.ai/code/session_01XG6sAAdkqTwWffqK5h4rH9
Chris LuandGitHub
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