smb3: add mount option to allow RW caching of share accessed by only 1 client

If a share is known to be only to be accessed by one client, we
can aggressively cache writes not just reads to it.

Add "cache=" option (cache=singleclient) for mounting read write shares
(that will not be read or written to from other clients while we have
it mounted) in order to improve performance.

Signed-off-by: Steve French <stfrench@microsoft.com>

4 files changed, 25 insertions, 3 deletions

diff --git a/fs/cifs/cifs_fs_sb.h b/fs/cifs/cifs_fs_sb.h
index 286a104c4761..6e7c4427369d 100644
--- a/fs/cifs/cifs_fs_sb.h
+++ b/fs/cifs/cifs_fs_sb.h
@@ -54,6 +54,7 @@
 #define CIFS_MOUNT_NO_DFS 0x8000000 /* disable DFS resolving */
 #define CIFS_MOUNT_MODE_FROM_SID 0x10000000 /* retrieve mode from special ACE */
 #define CIFS_MOUNT_RO_CACHE     0x20000000  /* assumes share will not change */
+#define CIFS_MOUNT_RW_CACHE     0x40000000  /* assumes only client accessing */
 
 struct cifs_sb_info {
         struct rb_root tlink_tree;
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 970251bc0661..de90e665ef11 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -400,6 +400,8 @@ cifs_show_cache_flavor(struct seq_file *s, struct cifs_sb_info *cifs_sb)
                 seq_puts(s, "strict");
         else if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_DIRECT_IO)
                 seq_puts(s, "none");
+        else if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_RW_CACHE)
+                seq_puts(s, "singleclient"); /* assume only one client access */
         else if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_RO_CACHE)
                 seq_puts(s, "ro"); /* read only caching assumed */
         else
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 3f12da7f2f7f..fa5abe3a8514 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -560,6 +560,7 @@ struct smb_vol {
         bool direct_io:1;
         bool strict_io:1; /* strict cache behavior */
         bool cache_ro:1;
+        bool cache_rw:1;
         bool remap:1;      /* set to remap seven reserved chars in filenames */
         bool sfu_remap:1;  /* remap seven reserved chars ala SFU */
         bool posix_paths:1; /* unset to not ask for posix pathnames. */
@@ -622,7 +623,7 @@ struct smb_vol {
                          CIFS_MOUNT_CIFS_BACKUPUID | CIFS_MOUNT_CIFS_BACKUPGID | \
                          CIFS_MOUNT_UID_FROM_ACL | CIFS_MOUNT_NO_HANDLE_CACHE | \
                          CIFS_MOUNT_NO_DFS | CIFS_MOUNT_MODE_FROM_SID | \
-                         CIFS_MOUNT_RO_CACHE)
+                         CIFS_MOUNT_RO_CACHE | CIFS_MOUNT_RW_CACHE)
 
 /**
  * Generic VFS superblock mount flags (s_flags) to consider when
@@ -1370,7 +1371,7 @@ void cifsFileInfo_put(struct cifsFileInfo *cifs_file);
 
 #define CIFS_CACHE_READ(cinode) ((cinode->oplock & CIFS_CACHE_READ_FLG) || (CIFS_SB(cinode->vfs_inode.i_sb)->mnt_cifs_flags & CIFS_MOUNT_RO_CACHE))
 #define CIFS_CACHE_HANDLE(cinode) (cinode->oplock & CIFS_CACHE_HANDLE_FLG)
-#define CIFS_CACHE_WRITE(cinode) (cinode->oplock & CIFS_CACHE_WRITE_FLG)
+#define CIFS_CACHE_WRITE(cinode) ((cinode->oplock & CIFS_CACHE_WRITE_FLG) || (CIFS_SB(cinode->vfs_inode.i_sb)->mnt_cifs_flags & CIFS_MOUNT_RW_CACHE))
 
 /*
  * One of these for each file inode
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 072c01f4e9c1..d9a995588c74 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -299,6 +299,7 @@ enum {
         Opt_cache_strict,
         Opt_cache_none,
         Opt_cache_ro,
+        Opt_cache_rw,
         Opt_cache_err
 };
 
@@ -307,6 +308,7 @@ static const match_table_t cifs_cacheflavor_tokens = {
         { Opt_cache_strict, "strict" },
         { Opt_cache_none, "none" },
         { Opt_cache_ro, "ro" },
+        { Opt_cache_rw, "singleclient" },
         { Opt_cache_err, NULL }
 };
 
@@ -1421,21 +1423,31 @@ cifs_parse_cache_flavor(char *value, struct smb_vol *vol)
                 vol->direct_io = false;
                 vol->strict_io = false;
                 vol->cache_ro = false;
+                vol->cache_rw = false;
                 break;
         case Opt_cache_strict:
                 vol->direct_io = false;
                 vol->strict_io = true;
                 vol->cache_ro = false;
+                vol->cache_rw = false;
                 break;
         case Opt_cache_none:
                 vol->direct_io = true;
                 vol->strict_io = false;
                 vol->cache_ro = false;
+                vol->cache_rw = false;
                 break;
         case Opt_cache_ro:
                 vol->direct_io = false;
                 vol->strict_io = false;
                 vol->cache_ro = true;
+                vol->cache_rw = false;
+                break;
+        case Opt_cache_rw:
+                vol->direct_io = false;
+                vol->strict_io = false;
+                vol->cache_ro = false;
+                vol->cache_rw = true;
                 break;
         default:
                 cifs_dbg(VFS, "bad cache= option: %s\n", value);
@@ -4054,6 +4066,10 @@ int cifs_setup_cifs_sb(struct smb_vol *pvolume_info,
         if (pvolume_info->cache_ro) {
                 cifs_dbg(VFS, "mounting share with read only caching. Ensure that the share will not be modified while in use.\n");
                 cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_RO_CACHE;
+        } else if (pvolume_info->cache_rw) {
+                cifs_dbg(VFS, "mounting share in single client RW caching mode. Ensure that no other systems will be accessing the share.\n");
+                cifs_sb->mnt_cifs_flags |= (CIFS_MOUNT_RO_CACHE |
+                                            CIFS_MOUNT_RW_CACHE);
         }
         if (pvolume_info->mfsymlinks) {
                 if (pvolume_info->sfu_emul) {
@@ -4203,8 +4219,10 @@ static int mount_get_conns(struct smb_vol *vol, struct cifs_sb_info *cifs_sb,
                         if (tcon->fsDevInfo.DeviceCharacteristics &
                             FILE_READ_ONLY_DEVICE)
                                 cifs_dbg(VFS, "mounted to read only share\n");
-                        else
+                        else if ((cifs_sb->mnt_cifs_flags &
+                                  CIFS_MOUNT_RW_CACHE) == 0)
                                 cifs_dbg(VFS, "read only mount of RW share\n");
+                        /* no need to log a RW mount of a typical RW share */
                 }
         }