Add support for original fallocate

In many cases the simple fallocate call is
a no op (since the file is already not sparse) or
can simply be converted from a sparse to a non-sparse
file if we are fallocating the whole file and keeping
the size.

Signed-off-by: Steven French <smfrench@gmail.com>

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index c5f521b..568f323 100644 (file)
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -1102,6 +1102,64 @@ static long smb3_punch_hole(struct file *file, struct cifs_tcon *tcon,
        return rc;
 }
 
+static long smb3_simple_falloc(struct file *file, struct cifs_tcon *tcon,
+                           loff_t off, loff_t len, bool keep_size)
+{
+       struct inode *inode;
+       struct cifsInodeInfo *cifsi;
+       struct cifsFileInfo *cfile = file->private_data;
+       long rc = -EOPNOTSUPP;
+       unsigned int xid;
+
+       xid = get_xid();
+
+       inode = cfile->dentry->d_inode;
+       cifsi = CIFS_I(inode);
+
+       /* if file not oplocked can't be sure whether asking to extend size */
+       if (!CIFS_CACHE_READ(cifsi))
+               if (keep_size == false)
+                       return -EOPNOTSUPP;
+
+       /*
+        * Files are non-sparse by default so falloc may be a no-op
+        * Must check if file sparse. If not sparse, and not extending
+        * then no need to do anything since file already allocated
+        */
+       if ((cifsi->cifsAttrs & FILE_ATTRIBUTE_SPARSE_FILE) == 0) {
+               if (keep_size == true)
+                       return 0;
+               /* check if extending file */
+               else if (i_size_read(inode) >= off + len)
+                       /* not extending file and already not sparse */
+                       return 0;
+               /* BB: in future add else clause to extend file */
+               else
+                       return -EOPNOTSUPP;
+       }
+
+       if ((keep_size == true) || (i_size_read(inode) >= off + len)) {
+               /*
+                * Check if falloc starts within first few pages of file
+                * and ends within a few pages of the end of file to
+                * ensure that most of file is being forced to be
+                * fallocated now. If so then setting whole file sparse
+                * ie potentially making a few extra pages at the beginning
+                * or end of the file non-sparse via set_sparse is harmless.
+                */
+               if ((off > 8192) || (off + len + 8192 < i_size_read(inode)))
+                       return -EOPNOTSUPP;
+
+               rc = smb2_set_sparse(xid, tcon, cfile, inode, false);
+       }
+       /* BB: else ... in future add code to extend file and set sparse */
+
+
+       free_xid(xid);
+       return rc;
+}
+
+
 static long smb3_fallocate(struct file *file, struct cifs_tcon *tcon, int mode,
                           loff_t off, loff_t len)
 {
@@ -1112,7 +1170,10 @@ static long smb3_fallocate(struct file *file, struct cifs_tcon *tcon, int mode,
                if (mode & FALLOC_FL_KEEP_SIZE)
                        return smb3_zero_range(file, tcon, off, len, true);
                return smb3_zero_range(file, tcon, off, len, false);
-       }
+       } else if (mode == FALLOC_FL_KEEP_SIZE)
+               return smb3_simple_falloc(file, tcon, off, len, true);
+       else if (mode == 0)
+               return smb3_simple_falloc(file, tcon, off, len, false);
 
        return -EOPNOTSUPP;
 }