Re: [PATCH] ntfs: exclude DOS aliases from VFS link count
From: liubaolin
Date: Thu Sep 24 2026 - 04:44:02 EST
在 2026/9/24 12:17, Michael Woolweaver 写道:
NTFS counts each $FILE_NAME attribute in the MFT record link_count.
A file with separate Win32 and DOS 8.3 names therefore has a link_count
of two even though the DOS name is an alias and does not represent a
separate VFS hard link.
ntfs_read_locked_inode() copies the MFT link_count directly to i_nlink,
causing stat() to report an extra hard link for files with a separate
DOS alias.
The same distinction is needed when unlinking. ntfs_delete() removes
both the DOS and Win32 $FILE_NAME attributes, decrementing the on-disk
link_count for each, but it must decrement the VFS link count only for
the Win32 name. Otherwise a real hard link can reach i_nlink zero while
another VFS-visible name still exists.
Count non-DOS $FILE_NAME attributes when initializing i_nlink, while
still verifying that the MFT link_count matches the total number of
name attributes. Do not drop i_nlink when ntfs_delete() removes a DOS
alias.
This was reproduced with a file containing separate Win32 and DOS
names. Its MFT link_count was 2 while stat() incorrectly reported 2
links. With the fix, stat() reports 1.
After adding a real POSIX hard link, the MFT contained three
$FILE_NAME attributes while the VFS correctly reported two links.
Removing the Win32/DOS pair left the POSIX hard link with both the MFT
link_count and VFS i_nlink equal to 1.
The fix was runtime-tested with fs/ntfs on a disposable NTFS image and
compile-tested on ntfs-next with W=1. checkpatch.pl reports no issues.
Fixes: 1e9ea7e04472 ("Revert "fs: Remove NTFS classic"")
Assisted-by: LLM
Signed-off-by: Michael Woolweaver <michael@xxxxxxxxxxxxxx>
---
fs/ntfs/inode.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++++
fs/ntfs/namei.c | 5 +++-
2 files changed, 81 insertions(+), 1 deletion(-)
diff --git a/fs/ntfs/inode.c b/fs/ntfs/inode.c
index 9583b2c6c7a2..74a0d9d1e82b 100644
--- a/fs/ntfs/inode.c
+++ b/fs/ntfs/inode.c
@@ -621,6 +621,67 @@ static int ntfs_is_extended_system_file(struct ntfs_attr_search_ctx *ctx)
return 0; /* NO, it is not an extended system file. */
}
+/*
+ * ntfs_count_vfs_links - count VFS-visible hard links
+ * @ctx: initialized attribute search context
+ *
+ * The MFT link count counts all $FILE_NAME attributes. A separate DOS 8.3
+ * name therefore contributes to the on-disk count even though it is an alias
+ * for its Win32 name and does not represent another VFS hard link.
+ *
+ * Return the number of VFS-visible links or -errno on error.
+ */
+static int ntfs_count_vfs_links(struct ntfs_attr_search_ctx *ctx)
+{
+ unsigned int expected, names = 0, links = 0;
+ int err;
+
+ expected = le16_to_cpu(ctx->mrec->link_count);
+ ntfs_attr_reinit_search_ctx(ctx);
Hi Michael,
Could we reinitialize the search context before reading link_count?
ntfs_attr_reinit_search_ctx(ctx);
expected = le16_to_cpu(ctx->mrec->link_count);
This ensures the count is read from the base MFT record even if the incoming context points to an extent record.
Thanks,
Baolin.
+
+ while (!(err = ntfs_attr_lookup(AT_FILE_NAME, NULL, 0, 0, 0, NULL, 0,
+ ctx))) {
+ struct attr_record *attr = ctx->attr;
+ struct file_name_attr *fn;
+ u32 attr_len, value_len;
+ u16 value_off;
+
+ if (unlikely(attr->non_resident))
+ goto corrupt;
+
+ attr_len = le32_to_cpu(attr->length);
+ value_len = le32_to_cpu(attr->data.resident.value_length);
+ value_off = le16_to_cpu(attr->data.resident.value_offset);
+
+ if (unlikely(value_off > attr_len ||
+ value_len > attr_len - value_off ||
+ value_len < offsetof(struct file_name_attr, file_name)))
+ goto corrupt;
+
+ fn = (struct file_name_attr *)((u8 *)attr + value_off);
+ names++;
+ if (fn->file_name_type != FILE_NAME_DOS)
+ links++;
+ }
+
+ if (unlikely(err != -ENOENT))
+ return err;
+
+ if (unlikely(names != expected || !links)) {
+ ntfs_error(ctx->ntfs_ino->vol->sb,
+ "Inode link count doesn't match file name attributes. You should run chkdsk.");
+ return -EIO;
+ }
+
+ ntfs_attr_reinit_search_ctx(ctx);
+ return links;
+
+corrupt:
+ ntfs_error(ctx->ntfs_ino->vol->sb,
+ "Corrupt file name attribute. You should run chkdsk.");
+ return -EIO;
+}
+
static struct lock_class_key ntfs_dir_inval_lock_key;
void ntfs_set_vfs_operations(struct inode *inode, mode_t mode, dev_t dev)
@@ -872,6 +933,22 @@ static int ntfs_read_locked_inode(struct inode *vi)
}
}
skip_attr_list_load:
+ /*
+ * The MFT link count includes separate DOS 8.3 aliases. Once the
+ * attribute list is available, derive the VFS link count from the
+ * $FILE_NAME namespaces instead.
+ */
+ if (!(m->flags & MFT_RECORD_IS_DIRECTORY) && vi->i_ino != FILE_MFT) {
+ int nr_links;
+
+ nr_links = ntfs_count_vfs_links(ctx);
+ if (unlikely(nr_links < 0)) {
+ err = nr_links;
+ goto unm_err_out;
+ }
+ set_nlink(vi, nr_links);
+ }
+
err = ntfs_attr_lookup(AT_EA_INFORMATION, NULL, 0, 0, 0, NULL, 0, ctx);
if (!err) {
NInoSetHasEA(ni);
diff --git a/fs/ntfs/namei.c b/fs/ntfs/namei.c
index 75e201096525..891ee697c0d2 100644
--- a/fs/ntfs/namei.c
+++ b/fs/ntfs/namei.c
@@ -829,6 +829,7 @@ static int ntfs_delete(struct ntfs_inode *ni, struct ntfs_inode *dir_ni,
struct file_name_attr *fn = NULL;
bool looking_for_dos_name = false, looking_for_win32_name = false;
bool case_sensitive_match = true;
+ bool is_dos_name;
int err = 0;
struct mft_record *ni_mrec;
struct super_block *sb;
@@ -932,6 +933,8 @@ static int ntfs_delete(struct ntfs_inode *ni, struct ntfs_inode *dir_ni,
if (err)
goto err_out;
+ is_dos_name = fn->file_name_type == FILE_NAME_DOS;
+
err = ntfs_index_remove(dir_ni, fn, le32_to_cpu(actx->attr->data.resident.value_length));
if (err)
goto err_out;
@@ -942,7 +945,7 @@ static int ntfs_delete(struct ntfs_inode *ni, struct ntfs_inode *dir_ni,
ni_mrec = actx->base_mrec ? actx->base_mrec : actx->mrec;
ni_mrec->link_count = cpu_to_le16(le16_to_cpu(ni_mrec->link_count) - 1);
- if (!S_ISDIR(VFS_I(ni)->i_mode))
+ if (!S_ISDIR(VFS_I(ni)->i_mode) && !is_dos_name)
drop_nlink(VFS_I(ni));
mark_mft_record_dirty(ni);
base-commit: 401898d748fcc8e19ceea1a37ed0de9075fe9ff2