copy_file_range: truncate write if it would exceed RLIMIT_FSIZE

[asomers]

Summary

copy_file_range: truncate write if it would exceed RLIMIT_FSIZE

PR: 266611
MFC after: 2 weeks

Test Plan

test case added for fusefs. Manual testing for UFS, ZFS, tmpfs, msdosfs, and nfs.

[kib]

Use of vn_rlimit_fsizex() requires finishing VOP with vn_rlimit_fsizex_res().
It is strange for nfs to obey new behavior for vop copy_range, but not for write (I did not converted nfs).

[asomers]

In D36706#833361, @kib wrote:

Use of vn_rlimit_fsizex() requires finishing VOP with vn_rlimit_fsizex_res().

That's only so the caller will see the correct value of uio_resid, right? For VOP_COPY_FILE_RANGE, the caller does not provide a struct uio. Instead, it's only necessary to return the number of bytes copied in *ap->a_lenp , AFAICT.

It is strange for nfs to obey new behavior for vop copy_range, but not for write (I did not converted nfs).

I could try to fix that one too.

[kib]

In D36706#833365, @asomers wrote:

In D36706#833361, @kib wrote:

Use of vn_rlimit_fsizex() requires finishing VOP with vn_rlimit_fsizex_res().

That's only so the caller will see the correct value of uio_resid, right? For VOP_COPY_FILE_RANGE, the caller does not provide a struct uio. Instead, it's only necessary to return the number of bytes copied in *ap->a_lenp , AFAICT.

Right now yes, but I considered it the current implementation detail. At least please add a comment explaining why _res() is not called, but I consider it fragile.

[asomers]

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