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

[NeilBrown <neilb@suse.com>]

On Sun, Nov 04 2018, James Simmons wrote:

>> On Thu, Oct 18 2018, NeilBrown wrote:
>> 
>> > On Sun, Oct 14 2018, James Simmons wrote:
>> >
>> >> From: Frank Zago <fzago@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@cray.com>
>> >> WC-bug-id: https://jira.whamcloud.com/browse/LU-9468
>> >> Reviewed-on: https://review.whamcloud.com/26992
>> >> Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
>> >> Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
>> >> Signed-off-by: James Simmons <jsimmons@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
>> >
>> > This is wrong.  We should fix in_compat_syscall(), not work around it
>> > here.
>> > (and then there is that fact that the patch changes 'int' to 'bool'
>> > without explaining that in the change description).
>> >
>> > I've sent a query to some relevant people (Cc:ed to James) to ask about
>> > fixing in_compat_syscall().
>> 
>> Upstream say in_compat_syscall() should only be called from a syscall,
>> so I have change the patch to the below.
>> 
>> We probably need to remove this in_compat_syscall() before going
>> mainline.
>
> Do you know the progress of this work?
>  

Below is the code that I currently have.
It avoids making a special case of X86_X32 - I should update
the comment to reflect that.

I've haven't given much thought yet to removing the need for
in_compat_syscall().  I need to make sure I understand exactly why
it is currently needed first.

NeilBrown


commit c69633550256d1a68306caf4f67a7d58ba8763e8
Author: Frank Zago <fzago@cray.com>
Date:   Sun Oct 14 14:58:05 2018 -0400

    lustre: llite: fix for stat under kthread and X86_X32
    
    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@cray.com>
    WC-bug-id: https://jira.whamcloud.com/browse/LU-9468
    Reviewed-on: https://review.whamcloud.com/26992
    Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
    Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
    Signed-off-by: James Simmons <jsimmons@infradead.org>
    Signed-off-by: NeilBrown <neilb@suse.com>

diff --git a/drivers/staging/lustre/lustre/llite/dir.c b/drivers/staging/lustre/lustre/llite/dir.c
index 231b351536bf..19c5e9cee3f9 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 30f17eaa6b2c..20a3c749f085 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 dcb2fed7a350..26c35f5d28a6 100644
--- a/drivers/staging/lustre/lustre/llite/llite_internal.h
+++ b/drivers/staging/lustre/lustre/llite/llite_internal.h
@@ -651,15 +651,27 @@ 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;
-#elif defined(CONFIG_COMPAT)
-	return unlikely(in_compat_syscall() ||
-			(sbi->ll_flags & LL_SBI_32BIT_API));
+	return true;
+#else
+	if (unlikely(sbi->ll_flags & LL_SBI_32BIT_API))
+		return true;
+
+#if defined(CONFIG_COMPAT)
+	/* in_compat_syscall() is only meaningful inside a syscall.
+	 * As this can be called from a kthread (e.g. nfsd), we
+	 * need to catch that case first.  kthreads never need the
+	 * 32bit api.
+	 */
+	if (current->flags & PF_KTHREAD)
+		return false;
+
+	return unlikely(in_compat_syscall());
 #else
-	return unlikely(sbi->ll_flags & LL_SBI_32BIT_API);
+	return false;
+#endif
 #endif
 }
 
@@ -1353,7 +1365,7 @@ extern u16 cl_inode_fini_refcheck;
 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 */
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 832 bytes
Desc: not available
URL: <http://lists.lustre.org/pipermail/lustre-devel-lustre.org/attachments/20181105/d9e78cd5/attachment-0001.sig>