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This reverts commit290434474c. That commit broke cache=mmap, a mode that doesn't cache metadata, but still has writeback cache. In commit290434474c("fs/9p: Refresh metadata in d_revalidate for uncached mode too") we considered metadata cache to be enough to not look at the server, but in writeback cache too looking at the server size would make the vfs consider the file has been truncated before the data has been flushed out, making the following repro fail (nothing is ever read back, the resulting file ends up with no data written) ``` #include <fcntl.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> char buf[4096]; int main(int argc, char *argv[]) { int ret, i; int fdw, fdr; if (argc < 2) return 1; fdw = openat(AT_FDCWD, argv[1], O_RDWR|O_CREAT|O_EXCL|O_CLOEXEC, 0600); if (fdw < 0) { fprintf(stderr, "cannot open fdw\n"); return 1; } write(fdw, buf, sizeof(buf)); fdr = openat(AT_FDCWD, argv[1], O_RDONLY|O_CLOEXEC); if (fdr < 0) { fprintf(stderr, "cannot open fdr\n"); close(fdw); return 1; } for (i = 0; i < 10; i++) { ret = read(fdr, buf, sizeof(buf)); fprintf(stderr, "i: %d, read returns %d\n", i, ret); } close(fdr); close(fdw); return 0; } ``` There is a fix for this particular reproducer but it looks like there are other problems around metadata refresh (e.g. around file rename), so revert this to avoid d_revalidate in uncached mode for now. Reported-by: Song Liu <song@kernel.org> Link: https://lkml.kernel.org/r/CAHzjS_u_SYdt5=2gYO_dxzMKXzGMt-TfdE_ueowg-Hq5tRCAiw@mail.gmail.com Reported-by: Andrii Nakryiko <andrii.nakryiko@gmail.com> Link: https://lore.kernel.org/bpf/CAEf4BzZbCE4tLoDZyUf_aASpgAGFj75QMfSXX4a4dLYixnOiLg@mail.gmail.com/ Fixes:290434474c("fs/9p: Refresh metadata in d_revalidate for uncached mode too") Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>