[CIFS] reopen file via newer posix open protocol operation if available

If the network connection crashes, and we have to reopen files, preferentially
use the newer cifs posix open protocol operation if the server supports it.
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/cifsproto.h

@@ -92,6 +92,9 @@ extern u64 cifs_UnixTimeToNT(struct timespec);
 extern __le64 cnvrtDosCifsTm(__u16 date, __u16 time);
 extern struct timespec cnvrtDosUnixTm(__u16 date, __u16 time);
 
+extern int cifs_posix_open(char *full_path, struct inode **pinode,
+			   struct super_block *sb, int mode, int oflags,
+			   int *poplock, __u16 *pnetfid, int xid);
 extern void posix_fill_in_inode(struct inode *tmp_inode,
 				FILE_UNIX_BASIC_INFO *pData, int isNewInode);
 extern struct inode *cifs_new_inode(struct super_block *sb, __u64 *inum);

fs/cifs/dir.c

@@ -129,7 +129,7 @@ build_path_from_dentry(struct dentry *direntry)
 	return full_path;
 }
 
-static int cifs_posix_open(char *full_path, struct inode **pinode,
+int cifs_posix_open(char *full_path, struct inode **pinode,
 		    struct super_block *sb, int mode, int oflags,
 		    int *poplock, __u16 *pnetfid, int xid)
 {
@@ -187,7 +187,9 @@ static int cifs_posix_open(char *full_path, struct inode **pinode,
 	if (!pinode)
 		goto posix_open_ret; /* caller does not need info */
 
+	if (*pinode == NULL)
 		*pinode = cifs_new_inode(sb, &presp_data->UniqueId);
+	/* else an inode was passed in. Update its info, don't create one */
 
 	/* We do not need to close the file if new_inode fails since
 	   the caller will retry qpathinfo as long as inode is null */

fs/cifs/file.c

@@ -78,8 +78,36 @@ static inline int cifs_convert_flags(unsigned int flags)
 	return (READ_CONTROL | FILE_WRITE_ATTRIBUTES | FILE_READ_ATTRIBUTES |
 		FILE_WRITE_EA | FILE_APPEND_DATA | FILE_WRITE_DATA |
 		FILE_READ_DATA);
+}
 
+static inline fmode_t cifs_posix_convert_flags(unsigned int flags)
+{
+	fmode_t posix_flags = 0;
 
+	if ((flags & O_ACCMODE) == O_RDONLY)
+		posix_flags = FMODE_READ;
+	else if ((flags & O_ACCMODE) == O_WRONLY)
+		posix_flags = FMODE_WRITE;
+	else if ((flags & O_ACCMODE) == O_RDWR) {
+		/* GENERIC_ALL is too much permission to request
+		   can cause unnecessary access denied on create */
+		/* return GENERIC_ALL; */
+		posix_flags = FMODE_READ | FMODE_WRITE;
+	}
+	/* can not map O_CREAT or O_EXCL or O_TRUNC flags when
+	   reopening a file.  They had their effect on the original open */
+	if (flags & O_APPEND)
+		posix_flags |= (fmode_t)O_APPEND;
+	if (flags & O_SYNC)
+		posix_flags |= (fmode_t)O_SYNC;
+	if (flags & O_DIRECTORY)
+		posix_flags |= (fmode_t)O_DIRECTORY;
+	if (flags & O_NOFOLLOW)
+		posix_flags |= (fmode_t)O_NOFOLLOW;
+	if (flags & O_DIRECT)
+		posix_flags |= (fmode_t)O_DIRECT;
+
+	return posix_flags;
 }
 
 static inline int cifs_get_disposition(unsigned int flags)
@@ -349,7 +377,7 @@ static int cifs_reopen_file(struct file *file, bool can_flush)
 	int rc = -EACCES;
 	int xid, oplock;
 	struct cifs_sb_info *cifs_sb;
-	struct cifsTconInfo *pTcon;
+	struct cifsTconInfo *tcon;
 	struct cifsFileInfo *pCifsFile;
 	struct cifsInodeInfo *pCifsInode;
 	struct inode *inode;
@@ -387,7 +415,7 @@ static int cifs_reopen_file(struct file *file, bool can_flush)
 	}
 
 	cifs_sb = CIFS_SB(inode->i_sb);
-	pTcon = cifs_sb->tcon;
+	tcon = cifs_sb->tcon;
 
 /* can not grab rename sem here because various ops, including
    those that already have the rename sem can end up causing writepage
@@ -404,20 +432,37 @@ static int cifs_reopen_file(struct file *file, bool can_flush)
 
 	cFYI(1, ("inode = 0x%p file flags 0x%x for %s",
 		 inode, file->f_flags, full_path));
-	desiredAccess = cifs_convert_flags(file->f_flags);
 
 	if (oplockEnabled)
 		oplock = REQ_OPLOCK;
 	else
 		oplock = 0;
 
+	if (tcon->unix_ext && (tcon->ses->capabilities & CAP_UNIX) &&
+	    (CIFS_UNIX_POSIX_PATH_OPS_CAP &
+			le64_to_cpu(tcon->fsUnixInfo.Capability))) {
+		int oflags = (int) cifs_posix_convert_flags(file->f_flags);
+		/* can not refresh inode info since size could be stale */
+		rc = cifs_posix_open(full_path, NULL, inode->i_sb,
+				     cifs_sb->mnt_file_mode /* ignored */,
+				     oflags, &oplock, &netfid, xid);
+		if (rc == 0) {
+			cFYI(1, ("posix reopen succeeded"));
+			goto reopen_success;
+		}
+		/* fallthrough to retry open the old way on errors, especially
+		   in the reconnect path it is important to retry hard */
+	}
+
+	desiredAccess = cifs_convert_flags(file->f_flags);
+
 	/* Can not refresh inode by passing in file_info buf to be returned
 	   by SMBOpen and then calling get_inode_info with returned buf
 	   since file might have write behind data that needs to be flushed
 	   and server version of file size can be stale. If we knew for sure
 	   that inode was not dirty locally we could do this */
 
-	rc = CIFSSMBOpen(xid, pTcon, full_path, disposition, desiredAccess,
+	rc = CIFSSMBOpen(xid, tcon, full_path, disposition, desiredAccess,
 			 CREATE_NOT_DIR, &netfid, &oplock, NULL,
 			 cifs_sb->local_nls, cifs_sb->mnt_cifs_flags &
 				CIFS_MOUNT_MAP_SPECIAL_CHR);
@@ -426,6 +471,7 @@ static int cifs_reopen_file(struct file *file, bool can_flush)
 		cFYI(1, ("cifs_open returned 0x%x", rc));
 		cFYI(1, ("oplock: %d", oplock));
 	} else {
+reopen_success:
 		pCifsFile->netfid = netfid;
 		pCifsFile->invalidHandle = false;
 		up(&pCifsFile->fh_sem);
@@ -439,7 +485,7 @@ static int cifs_reopen_file(struct file *file, bool can_flush)
 			   go to server to get inode info */
 				pCifsInode->clientCanCacheAll = false;
 				pCifsInode->clientCanCacheRead = false;
-				if (pTcon->unix_ext)
+				if (tcon->unix_ext)
 					rc = cifs_get_inode_info_unix(&inode,
 						full_path, inode->i_sb, xid);
 				else
@@ -467,7 +513,6 @@ static int cifs_reopen_file(struct file *file, bool can_flush)
 			cifs_relock_file(pCifsFile);
 		}
 	}
-
 	kfree(full_path);
 	FreeXid(xid);
 	return rc;