CVS commit: src/external/cddl/osnet/dist/uts/common/fs/zfs

["YAMAMOTO Takashi" <yamt%netbsd.org@localhost>]

Module Name:    src
Committed By:   yamt
Date:           Mon Mar 23 10:41:15 UTC 2026

Modified Files:
        src/external/cddl/osnet/dist/uts/common/fs/zfs: zfs_vnops.c

Log Message:
zfs: flush mmap pages on fsync

it seems the logic to flush page cache in fsync has been removed
during the initial port to netbsd. at that point it was probably ok
because we simply didn't support mmap. since then, mmap support has
been added. but the fsync logic has not been restored. it means that
mmap-modified pages are left dirty basically forever, unless the
application explicitly performs msync on them or page daemon tries
to reclaim them on system memory shortage. it's bad especially for
a file system like zfs because writing data to zfs involves complex
locking and memory allocations, and thus not safe in the context of
the page daemon.

this commit fixes (well, at least improves the situation a bit) by
putting back the page flushing logic.

ideally netbsd needs to have some throttling mechanism on
page-dirtying activities. i suppose such a mechanism can be
implemented in a mostly filesystem-independent manner.
(it was one of my motivations of yamt-pagecache branch.)


To generate a diff of this commit:
cvs rdiff -u -r1.92 -r1.93 \
    src/external/cddl/osnet/dist/uts/common/fs/zfs/zfs_vnops.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.