This is to support using open_by_handle_at(2) via io_uring. It is useful
for io_uring to request that opening a file via handle be completed
using only cached data, or fail with -EAGAIN if that is not possible.

The signature of xfs_nfs_get_inode() is extended with a new flags
argument that allows callers to specify XFS_IGET_INCORE.

That flag is set when the VFS passes the FILEID_CACHED flag via the
fileid_type argument.

Signed-off-by: Thomas Bertschinger <tahbertschinger@gmail.com>
Acked-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/xfs/xfs_export.c | 34 ++++++++++++++++++++++++++--------
 fs/xfs/xfs_export.h |  3 ++-
 fs/xfs/xfs_handle.c |  2 +-
 3 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/fs/xfs/xfs_export.c b/fs/xfs/xfs_export.c
index 201489d3de08..6a57ed8fd9b7 100644
--- a/fs/xfs/xfs_export.c
+++ b/fs/xfs/xfs_export.c
@@ -106,7 +106,8 @@ struct inode *
 xfs_nfs_get_inode(
 	struct super_block	*sb,
 	u64			ino,
-	u32			generation)
+	u32			generation,
+	uint			flags)
 {
  	xfs_mount_t		*mp = XFS_M(sb);
 	xfs_inode_t		*ip;
@@ -123,7 +124,9 @@ xfs_nfs_get_inode(
 	 * fine and not an indication of a corrupted filesystem as clients can
 	 * send invalid file handles and we have to handle it gracefully..
 	 */
-	error = xfs_iget(mp, NULL, ino, XFS_IGET_UNTRUSTED, 0, &ip);
+	flags |= XFS_IGET_UNTRUSTED;
+
+	error = xfs_iget(mp, NULL, ino, flags, 0, &ip);
 	if (error) {
 
 		/*
@@ -140,6 +143,10 @@ xfs_nfs_get_inode(
 		case -EFSCORRUPTED:
 			error = -ESTALE;
 			break;
+		case -ENODATA:
+			if (flags & XFS_IGET_INCORE)
+				error = -EAGAIN;
+			break;
 		default:
 			break;
 		}
@@ -170,10 +177,15 @@ xfs_nfs_get_inode(
 
 STATIC struct dentry *
 xfs_fs_fh_to_dentry(struct super_block *sb, struct fid *fid,
-		 int fh_len, int fileid_type)
+		 int fh_len, int fileid_type_flags)
 {
+	int			fileid_type = FILEID_TYPE(fileid_type_flags);
 	struct xfs_fid64	*fid64 = (struct xfs_fid64 *)fid;
 	struct inode		*inode = NULL;
+	uint			flags = 0;
+
+	if (fileid_type_flags & FILEID_CACHED)
+		flags = XFS_IGET_INCORE;
 
 	if (fh_len < xfs_fileid_length(fileid_type))
 		return NULL;
@@ -181,11 +193,11 @@ xfs_fs_fh_to_dentry(struct super_block *sb, struct fid *fid,
 	switch (fileid_type) {
 	case FILEID_INO32_GEN_PARENT:
 	case FILEID_INO32_GEN:
-		inode = xfs_nfs_get_inode(sb, fid->i32.ino, fid->i32.gen);
+		inode = xfs_nfs_get_inode(sb, fid->i32.ino, fid->i32.gen, flags);
 		break;
 	case FILEID_INO32_GEN_PARENT | XFS_FILEID_TYPE_64FLAG:
 	case FILEID_INO32_GEN | XFS_FILEID_TYPE_64FLAG:
-		inode = xfs_nfs_get_inode(sb, fid64->ino, fid64->gen);
+		inode = xfs_nfs_get_inode(sb, fid64->ino, fid64->gen, flags);
 		break;
 	}
 
@@ -194,10 +206,15 @@ xfs_fs_fh_to_dentry(struct super_block *sb, struct fid *fid,
 
 STATIC struct dentry *
 xfs_fs_fh_to_parent(struct super_block *sb, struct fid *fid,
-		 int fh_len, int fileid_type)
+		 int fh_len, int fileid_type_flags)
 {
+	int			fileid_type = FILEID_TYPE(fileid_type_flags);
 	struct xfs_fid64	*fid64 = (struct xfs_fid64 *)fid;
 	struct inode		*inode = NULL;
+	uint			flags = 0;
+
+	if (fileid_type_flags & FILEID_CACHED)
+		flags = XFS_IGET_INCORE;
 
 	if (fh_len < xfs_fileid_length(fileid_type))
 		return NULL;
@@ -205,11 +222,11 @@ xfs_fs_fh_to_parent(struct super_block *sb, struct fid *fid,
 	switch (fileid_type) {
 	case FILEID_INO32_GEN_PARENT:
 		inode = xfs_nfs_get_inode(sb, fid->i32.parent_ino,
-					      fid->i32.parent_gen);
+					      fid->i32.parent_gen, flags);
 		break;
 	case FILEID_INO32_GEN_PARENT | XFS_FILEID_TYPE_64FLAG:
 		inode = xfs_nfs_get_inode(sb, fid64->parent_ino,
-					      fid64->parent_gen);
+					      fid64->parent_gen, flags);
 		break;
 	}
 
@@ -248,4 +265,5 @@ const struct export_operations xfs_export_operations = {
 	.map_blocks		= xfs_fs_map_blocks,
 	.commit_blocks		= xfs_fs_commit_blocks,
 #endif
+	.flags			= EXPORT_OP_NONBLOCK,
 };
diff --git a/fs/xfs/xfs_export.h b/fs/xfs/xfs_export.h
index 3cd85e8901a5..9addfcd5b1e1 100644
--- a/fs/xfs/xfs_export.h
+++ b/fs/xfs/xfs_export.h
@@ -57,6 +57,7 @@ struct xfs_fid64 {
 /* This flag goes on the wire.  Don't play with it. */
 #define XFS_FILEID_TYPE_64FLAG	0x80	/* NFS fileid has 64bit inodes */
 
-struct inode *xfs_nfs_get_inode(struct super_block *sb, u64 ino, u32 gen);
+struct inode *xfs_nfs_get_inode(struct super_block *sb, u64 ino, u32 gen,
+				uint flags);
 
 #endif	/* __XFS_EXPORT_H__ */
diff --git a/fs/xfs/xfs_handle.c b/fs/xfs/xfs_handle.c
index f19fce557354..7d877ff504d6 100644
--- a/fs/xfs/xfs_handle.c
+++ b/fs/xfs/xfs_handle.c
@@ -193,7 +193,7 @@ xfs_khandle_to_inode(
 		return ERR_PTR(-EINVAL);
 
 	inode = xfs_nfs_get_inode(mp->m_super, handle->ha_fid.fid_ino,
-			handle->ha_fid.fid_gen);
+			handle->ha_fid.fid_gen, 0);
 	if (IS_ERR(inode))
 		return ERR_CAST(inode);
 
-- 
2.51.0