[lustre-devel] [PATCH 15/28] lustre: llite: fix for stat under kthread and X86_X32

[James Simmons]

From: Frank Zago <fzago at cray.com>

Under the following conditions, ll_getattr will flatten the inode
number when it shouldn't:

 - the X86_X32 architecture is defined CONFIG_X86_X32, and not even
   used,
 - ll_getattr is called from a kernel thread (though vfs_getattr for
   instance.)

This has the result that inode numbers are different whether the same
file is stat'ed from a kernel thread, or from a syscall. For instance,
4198401 vs. 144115205272502273.

ll_getattr calls ll_need_32bit_api to determine whether the task is 32
bits. When the combination is kthread+X86_X32, that function returns
that the task is 32 bits, which is incorrect, as the kernel is 64
bits.

The solution is to check whether the call is from a kernel thread
(which is 64 bits) and act consequently.

Signed-off-by: Frank Zago <fzago at cray.com>
WC-bug-id: https://jira.whamcloud.com/browse/LU-9468
Reviewed-on: https://review.whamcloud.com/26992
Reviewed-by: Andreas Dilger <adilger at whamcloud.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin at intel.com>
Signed-off-by: James Simmons <jsimmons at infradead.org>
---
 drivers/staging/lustre/lustre/llite/dir.c          |  6 +++---
 drivers/staging/lustre/lustre/llite/lcommon_cl.c   |  2 +-
 .../staging/lustre/lustre/llite/llite_internal.h   | 22 +++++++++++++++++-----
 3 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/drivers/staging/lustre/lustre/llite/dir.c b/drivers/staging/lustre/lustre/llite/dir.c
index 231b351..19c5e9c 100644
--- a/drivers/staging/lustre/lustre/llite/dir.c
+++ b/drivers/staging/lustre/lustre/llite/dir.c
@@ -202,7 +202,7 @@ int ll_dir_read(struct inode *inode, __u64 *ppos, struct md_op_data *op_data,
 {
 	struct ll_sb_info    *sbi	= ll_i2sbi(inode);
 	__u64		   pos		= *ppos;
-	int		   is_api32 = ll_need_32bit_api(sbi);
+	bool is_api32 = ll_need_32bit_api(sbi);
 	int		   is_hash64 = sbi->ll_flags & LL_SBI_64BIT_HASH;
 	struct page	  *page;
 	bool		   done = false;
@@ -296,7 +296,7 @@ static int ll_readdir(struct file *filp, struct dir_context *ctx)
 	struct ll_sb_info	*sbi	= ll_i2sbi(inode);
 	__u64 pos = lfd ? lfd->lfd_pos : 0;
 	int			hash64	= sbi->ll_flags & LL_SBI_64BIT_HASH;
-	int			api32	= ll_need_32bit_api(sbi);
+	bool api32 = ll_need_32bit_api(sbi);
 	struct md_op_data *op_data;
 	int			rc;
 
@@ -1674,7 +1674,7 @@ static loff_t ll_dir_seek(struct file *file, loff_t offset, int origin)
 	struct inode *inode = file->f_mapping->host;
 	struct ll_file_data *fd = LUSTRE_FPRIVATE(file);
 	struct ll_sb_info *sbi = ll_i2sbi(inode);
-	int api32 = ll_need_32bit_api(sbi);
+	bool api32 = ll_need_32bit_api(sbi);
 	loff_t ret = -EINVAL;
 
 	switch (origin) {
diff --git a/drivers/staging/lustre/lustre/llite/lcommon_cl.c b/drivers/staging/lustre/lustre/llite/lcommon_cl.c
index 30f17ea..20a3c74 100644
--- a/drivers/staging/lustre/lustre/llite/lcommon_cl.c
+++ b/drivers/staging/lustre/lustre/llite/lcommon_cl.c
@@ -267,7 +267,7 @@ void cl_inode_fini(struct inode *inode)
 /**
  * build inode number from passed @fid
  */
-__u64 cl_fid_build_ino(const struct lu_fid *fid, int api32)
+u64 cl_fid_build_ino(const struct lu_fid *fid, bool api32)
 {
 	if (BITS_PER_LONG == 32 || api32)
 		return fid_flatten32(fid);
diff --git a/drivers/staging/lustre/lustre/llite/llite_internal.h b/drivers/staging/lustre/lustre/llite/llite_internal.h
index dcb2fed..796a8ae 100644
--- a/drivers/staging/lustre/lustre/llite/llite_internal.h
+++ b/drivers/staging/lustre/lustre/llite/llite_internal.h
@@ -651,13 +651,25 @@ static inline struct inode *ll_info2i(struct ll_inode_info *lli)
 __u32 ll_i2suppgid(struct inode *i);
 void ll_i2gids(__u32 *suppgids, struct inode *i1, struct inode *i2);
 
-static inline int ll_need_32bit_api(struct ll_sb_info *sbi)
+static inline bool ll_need_32bit_api(struct ll_sb_info *sbi)
 {
 #if BITS_PER_LONG == 32
-	return 1;
+	return true;
 #elif defined(CONFIG_COMPAT)
-	return unlikely(in_compat_syscall() ||
-			(sbi->ll_flags & LL_SBI_32BIT_API));
+	if (unlikely(sbi->ll_flags & LL_SBI_32BIT_API))
+		return true;
+
+#ifdef CONFIG_X86_X32
+	/* in_compat_syscall() returns true when called from a kthread
+	 * and CONFIG_X86_X32 is enabled, which is wrong. So check
+	 * whether the caller comes from a syscall (ie. not a kthread)
+	 * before calling in_compat_syscall().
+	 */
+	if (current->flags & PF_KTHREAD)
+		return false;
+#endif
+
+	return unlikely(in_compat_syscall());
 #else
 	return unlikely(sbi->ll_flags & LL_SBI_32BIT_API);
 #endif
@@ -1353,7 +1365,7 @@ int cl_setattr_ost(struct cl_object *obj, const struct iattr *attr,
 int cl_file_inode_init(struct inode *inode, struct lustre_md *md);
 void cl_inode_fini(struct inode *inode);
 
-__u64 cl_fid_build_ino(const struct lu_fid *fid, int api32);
+u64 cl_fid_build_ino(const struct lu_fid *fid, bool api32);
 __u32 cl_fid_build_gen(const struct lu_fid *fid);
 
 #endif /* LLITE_INTERNAL_H */
-- 
1.8.3.1