Linux 4.11 compat: iops.getattr and friends

In torvalds/linux@a528d35, there are changes to the getattr family of functions,
struct kstat, and the interface of inode_operations .getattr.

The inode_operations .getattr and simple_getattr() interface changed to:

int (*getattr) (const struct path *, struct dentry *, struct kstat *,
    u32 request_mask, unsigned int query_flags)

The request_mask argument indicates which field(s) the caller intends to use.
Fields the caller has not specified via request_mask may be set in the returned
struct anyway, but their values may be approximate.

The query_flags argument indicates whether the filesystem must update
the attributes from the backing store.

Currently both fields are ignored.  It is possible that getattr-related
functions within zfs could be optimized based on the request_mask.

struct kstat includes new fields:
u32               result_mask;  /* What fields the user got */
u64               attributes;   /* See STATX_ATTR_* flags */
struct timespec   btime;        /* File creation time */

Fields attribute and btime are cleared; the result_mask reflects this.  These
appear to be optional based on simple_getattr() and vfs_getattr() within the
kernel, which take the same approach.

Reviewed-by: Chunwei Chen <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Olaf Faaland <[email protected]>
Closes #5875 

1 files changed, 43 insertions, 0 deletions

diff --git a/include/linux/vfs_compat.h b/include/linux/vfs_compat.h
index baa298018..cd22b522a 100644
--- a/include/linux/vfs_compat.h
+++ b/include/linux/vfs_compat.h
@@ -454,4 +454,47 @@ setattr_prepare(struct dentry *dentry, struct iattr *ia)
 }
 #endif
 
+/*
+ * 4.11 API change
+ * These macros are defined by kernel 4.11.  We define them so that the same
+ * code builds under kernels < 4.11 and >= 4.11.  The macros are set to 0 so
+ * that it will create obvious failures if they are accidentally used when built
+ * against a kernel >= 4.11.
+ */
+
+#ifndef STATX_BASIC_STATS
+#define	STATX_BASIC_STATS	0
+#endif
+
+#ifndef AT_STATX_SYNC_AS_STAT
+#define	AT_STATX_SYNC_AS_STAT	0
+#endif
+
+/*
+ * 4.11 API change
+ * 4.11 takes struct path *, < 4.11 takes vfsmount *
+ */
+
+#ifdef HAVE_VFSMOUNT_IOPS_GETATTR
+#define	ZPL_GETATTR_WRAPPER(func)					\
+static int								\
+func(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)	\
+{									\
+	struct path path = { .mnt = mnt, .dentry = dentry };		\
+	return func##_impl(&path, stat, STATX_BASIC_STATS,		\
+	    AT_STATX_SYNC_AS_STAT);					\
+}
+#elif defined(HAVE_PATH_IOPS_GETATTR)
+#define	ZPL_GETATTR_WRAPPER(func)					\
+static int								\
+func(const struct path *path, struct kstat *stat, u32 request_mask,	\
+    unsigned int query_flags)						\
+{									\
+	return (func##_impl(path, stat, request_mask, query_flags));	\
+}
+#else
+#error
+#endif
+
+
 #endif /* _ZFS_VFS_H */