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[2001:1c00:570d:ee00:69e4:e864:578d:bdb1]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b842a22ff58sm732503866b.6.2026.01.07.23.45.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 Jan 2026 23:45:24 -0800 (PST) From: Amir Goldstein To: Christian Brauner Cc: Miklos Szeredi , Al Viro , linux-fsdevel@vger.kernel.org, linux-unionfs@vger.kernel.org, Chunsheng Luo Subject: [PATCH v2] readdir: require opt-in for d_type flags Date: Thu, 8 Jan 2026 08:45:22 +0100 Message-ID: <20260108074522.3400998-1-amir73il@gmail.com> X-Mailer: git-send-email 2.52.0 Precedence: bulk X-Mailing-List: linux-unionfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Commit c31f91c6af96 ("fuse: don't allow signals to interrupt getdents copying") introduced the use of high bits in d_type as flags. However, overlayfs was not adapted to handle this change. In ovl_cache_entry_new(), the code checks if d_type == DT_CHR to determine if an entry might be a whiteout. When fuse is used as the lower layer and sets high bits in d_type, this comparison fails, causing whiteout files to not be recognized properly and resulting in incorrect overlayfs behavior. Fix this by requiring callers of iterate_dir() to opt-in for getting flag bits in d_type outside of S_DT_MASK. Fixes: c31f91c6af96 ("fuse: don't allow signals to interrupt getdents copying") Link: https://lore.kernel.org/all/20260107034551.439-1-luochunsheng@ustc.edu/ Link: https://github.com/containerd/stargz-snapshotter/issues/2214 Reported-by: Chunsheng Luo Reviewed-by: Chunsheng Luo Tested-by: Chunsheng Luo Signed-off-by: Amir Goldstein --- Christian, "Not pretty, but fine." [0] This is what you had to say on the Fixes commit ;) Maybe this will be finer... I was considering whether or not a mention in porting.rst is due. My conclusion was that the regressing commit might have needed to mention a change of vfs API, but this fix brings the vfs API back to conform to pre v6.16 semantics, so no porting instructions apply. Thanks, Amir. Chages sinse v1: - Rename s/dt_flag_mask/dt_flags_mask/ - Add Test/Reviewd-by [0] https://lore.kernel.org/linux-fsdevel/20250515-antlitz-aufzwingen-cdba155ce864@brauner/ fs/readdir.c | 3 +++ include/linux/fs.h | 6 +++++- 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/fs/readdir.c b/fs/readdir.c index 7764b86389788..73707b6816e9a 100644 --- a/fs/readdir.c +++ b/fs/readdir.c @@ -316,6 +316,7 @@ SYSCALL_DEFINE3(getdents, unsigned int, fd, struct getdents_callback buf = { .ctx.actor = filldir, .ctx.count = count, + .ctx.dt_flags_mask = FILLDIR_FLAG_NOINTR, .current_dir = dirent }; int error; @@ -400,6 +401,7 @@ SYSCALL_DEFINE3(getdents64, unsigned int, fd, struct getdents_callback64 buf = { .ctx.actor = filldir64, .ctx.count = count, + .ctx.dt_flags_mask = FILLDIR_FLAG_NOINTR, .current_dir = dirent }; int error; @@ -569,6 +571,7 @@ COMPAT_SYSCALL_DEFINE3(getdents, unsigned int, fd, struct compat_getdents_callback buf = { .ctx.actor = compat_filldir, .ctx.count = count, + .ctx.dt_flags_mask = FILLDIR_FLAG_NOINTR, .current_dir = dirent, }; int error; diff --git a/include/linux/fs.h b/include/linux/fs.h index f5c9cf28c4dcf..a01621fa636a6 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1855,6 +1855,8 @@ struct dir_context { * INT_MAX unlimited */ int count; + /* @actor supports these flags in d_type high bits */ + unsigned int dt_flags_mask; }; /* If OR-ed with d_type, pending signals are not checked */ @@ -3524,7 +3526,9 @@ static inline bool dir_emit(struct dir_context *ctx, const char *name, int namelen, u64 ino, unsigned type) { - return ctx->actor(ctx, name, namelen, ctx->pos, ino, type); + unsigned int dt_mask = S_DT_MASK | ctx->dt_flags_mask; + + return ctx->actor(ctx, name, namelen, ctx->pos, ino, type & dt_mask); } static inline bool dir_emit_dot(struct file *file, struct dir_context *ctx) { -- 2.52.0