From: Dominique Martinet Date: Tue, 21 Oct 2025 21:33:42 +0000 (+0900) Subject: Revert "fs/9p: Refresh metadata in d_revalidate for uncached mode too" X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=43c36a56ccf6d9b07b4b3f4f614756e687dcdc01;p=users%2Fhch%2Fmisc.git Revert "fs/9p: Refresh metadata in d_revalidate for uncached mode too" This reverts commit 290434474c332a2ba9c8499fe699c7f2e1153280. That commit broke cache=mmap, a mode that doesn't cache metadata, but still has writeback cache. In commit 290434474c33 ("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 #include #include #include 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 Link: https://lkml.kernel.org/r/CAHzjS_u_SYdt5=2gYO_dxzMKXzGMt-TfdE_ueowg-Hq5tRCAiw@mail.gmail.com Reported-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/CAEf4BzZbCE4tLoDZyUf_aASpgAGFj75QMfSXX4a4dLYixnOiLg@mail.gmail.com/ Fixes: 290434474c33 ("fs/9p: Refresh metadata in d_revalidate for uncached mode too") Signed-off-by: Dominique Martinet --- diff --git a/fs/9p/vfs_dentry.c b/fs/9p/vfs_dentry.c index f3248a3e5402..c1acbc98465d 100644 --- a/fs/9p/vfs_dentry.c +++ b/fs/9p/vfs_dentry.c @@ -66,7 +66,6 @@ static int __v9fs_lookup_revalidate(struct dentry *dentry, unsigned int flags) struct p9_fid *fid; struct inode *inode; struct v9fs_inode *v9inode; - unsigned int cached; if (flags & LOOKUP_RCU) return -ECHILD; @@ -76,11 +75,7 @@ static int __v9fs_lookup_revalidate(struct dentry *dentry, unsigned int flags) goto out_valid; v9inode = V9FS_I(inode); - struct v9fs_session_info *v9ses = v9fs_inode2v9ses(inode); - - cached = v9ses->cache & (CACHE_META | CACHE_LOOSE); - - if (!cached || v9inode->cache_validity & V9FS_INO_INVALID_ATTR) { + if (v9inode->cache_validity & V9FS_INO_INVALID_ATTR) { int retval; struct v9fs_session_info *v9ses; @@ -114,6 +109,7 @@ static int __v9fs_lookup_revalidate(struct dentry *dentry, unsigned int flags) p9_debug(P9_DEBUG_VFS, "refresh inode: dentry = %pd (%p), got error %pe\n", dentry, dentry, ERR_PTR(retval)); + if (retval < 0) return retval; } } @@ -150,8 +146,6 @@ const struct dentry_operations v9fs_cached_dentry_operations = { }; const struct dentry_operations v9fs_dentry_operations = { - .d_revalidate = v9fs_lookup_revalidate, - .d_weak_revalidate = __v9fs_lookup_revalidate, .d_release = v9fs_dentry_release, .d_unalias_trylock = v9fs_dentry_unalias_trylock, .d_unalias_unlock = v9fs_dentry_unalias_unlock, diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c index 69f378a83775..d0c77ec31b1d 100644 --- a/fs/9p/vfs_inode.c +++ b/fs/9p/vfs_inode.c @@ -1339,14 +1339,8 @@ int v9fs_refresh_inode(struct p9_fid *fid, struct inode *inode) * Don't update inode if the file type is different */ umode = p9mode2unixmode(v9ses, st, &rdev); - if (inode_wrong_type(inode, umode)) { - /* - * Do this as a way of letting the caller know the inode should not - * be reused - */ - v9fs_invalidate_inode_attr(inode); + if (inode_wrong_type(inode, umode)) goto out; - } /* * We don't want to refresh inode->i_size, diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c index 0b404e8484d2..be297e335468 100644 --- a/fs/9p/vfs_inode_dotl.c +++ b/fs/9p/vfs_inode_dotl.c @@ -897,14 +897,8 @@ int v9fs_refresh_inode_dotl(struct p9_fid *fid, struct inode *inode) /* * Don't update inode if the file type is different */ - if (inode_wrong_type(inode, st->st_mode)) { - /* - * Do this as a way of letting the caller know the inode should not - * be reused - */ - v9fs_invalidate_inode_attr(inode); + if (inode_wrong_type(inode, st->st_mode)) goto out; - } /* * We don't want to refresh inode->i_size,