[PATCH 4/7] cifs: define variable sized buffer for querydir responses

[nspmangalore@gmail.com]

From: Shyam Prasad N <sprasad@microsoft.com>

QueryDirectory responses today are stored in one of two fixed
sized buffers: smallbuf (448 bytes) or bigbuf (16KB). These are
borrowed from server struct and are not sufficient for large-sized
query dir operations.

With this change we will now define a new buffer type specifically
for cifs_search_info to hold variable sized responses. These will
be allocated by kmalloc and freed by kfree.

Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
---
 fs/smb/client/cifsglob.h |  2 ++
 fs/smb/client/file.c     |  2 ++
 fs/smb/client/readdir.c  |  2 ++
 fs/smb/client/smb2pdu.c  | 14 +++++++++++---
 4 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index 709e96e077916..8d089ba08e3e5 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -1394,6 +1394,7 @@ struct cifs_search_info {
 	bool emptyDir:1;
 	bool unicode:1;
 	bool smallBuf:1; /* so we know which buf_release function to call */
+	bool is_dynamic_buf:1; /* dynamically allocated buffer - can be variable size */
 };
 
 #define ACL_NO_MODE	((umode_t)(-1))
@@ -1907,6 +1908,7 @@ enum cifs_find_flags {
 #define   CIFS_NO_BUFFER        0    /* Response buffer not returned */
 #define   CIFS_SMALL_BUFFER     1
 #define   CIFS_LARGE_BUFFER     2
+#define   CIFS_DYNAMIC_BUFFER   3    /* Dynamically allocated buffer */
 #define   CIFS_IOVEC            4    /* array of response buffers */
 
 /* Type of Request to SendReceive2 */
diff --git a/fs/smb/client/file.c b/fs/smb/client/file.c
index a69e05f86d7e2..6a1419d59ed5a 100644
--- a/fs/smb/client/file.c
+++ b/fs/smb/client/file.c
@@ -1546,6 +1546,8 @@ int cifs_closedir(struct inode *inode, struct file *file)
 		cfile->srch_inf.ntwrk_buf_start = NULL;
 		if (cfile->srch_inf.smallBuf)
 			cifs_small_buf_release(buf);
+		else if (cfile->srch_inf.is_dynamic_buf)
+			kfree(buf);
 		else
 			cifs_buf_release(buf);
 	}
diff --git a/fs/smb/client/readdir.c b/fs/smb/client/readdir.c
index be22bbc4a65a0..b50efd9b9e1d2 100644
--- a/fs/smb/client/readdir.c
+++ b/fs/smb/client/readdir.c
@@ -732,6 +732,8 @@ find_cifs_entry(const unsigned int xid, struct cifs_tcon *tcon, loff_t pos,
 			if (cfile->srch_inf.smallBuf)
 				cifs_small_buf_release(cfile->srch_inf.
 						ntwrk_buf_start);
+			else if (cfile->srch_inf.is_dynamic_buf)
+				kfree(cfile->srch_inf.ntwrk_buf_start);
 			else
 				cifs_buf_release(cfile->srch_inf.
 						ntwrk_buf_start);
diff --git a/fs/smb/client/smb2pdu.c b/fs/smb/client/smb2pdu.c
index 5188218c25be4..49dca84b169e6 100644
--- a/fs/smb/client/smb2pdu.c
+++ b/fs/smb/client/smb2pdu.c
@@ -5625,6 +5625,8 @@ smb2_parse_query_directory(struct cifs_tcon *tcon,
 	if (srch_inf->ntwrk_buf_start) {
 		if (srch_inf->smallBuf)
 			cifs_small_buf_release(srch_inf->ntwrk_buf_start);
+		else if (srch_inf->is_dynamic_buf)
+			kfree(srch_inf->ntwrk_buf_start);
 		else
 			cifs_buf_release(srch_inf->ntwrk_buf_start);
 	}
@@ -5644,12 +5646,18 @@ smb2_parse_query_directory(struct cifs_tcon *tcon,
 	cifs_dbg(FYI, "num entries %d last_index %lld srch start %p srch end %p\n",
 		 srch_inf->entries_in_buffer, srch_inf->index_of_last_entry,
 		 srch_inf->srch_entries_start, srch_inf->last_entry);
-	if (resp_buftype == CIFS_LARGE_BUFFER)
+	if (resp_buftype == CIFS_LARGE_BUFFER) {
 		srch_inf->smallBuf = false;
-	else if (resp_buftype == CIFS_SMALL_BUFFER)
+		srch_inf->is_dynamic_buf = false;
+	} else if (resp_buftype == CIFS_SMALL_BUFFER) {
 		srch_inf->smallBuf = true;
-	else
+		srch_inf->is_dynamic_buf = false;
+	} else if (resp_buftype == CIFS_DYNAMIC_BUFFER) {
+		srch_inf->smallBuf = false;
+		srch_inf->is_dynamic_buf = true;
+	} else {
 		cifs_tcon_dbg(VFS, "Invalid search buffer type\n");
+	}
 
 	return 0;
 }
-- 
2.43.0