[SMB3] add mount option "nosparse"

[SMB3] add mount option "nosparse"

[Steve French]

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To reduce risk of applications breaking that mount to servers
with only partial sparse file support, add optional mount parm
 "nosparse" which disables setting files sparse (and thus
 will return EOPNOTSUPP on certain fallocate operations).


-- 
Thanks,

Steve

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From 8f0842bee7c70b1367486c79f495df38d2c8111c Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@microsoft.com>
Date: Mon, 23 May 2022 23:17:12 -0500
Subject: [PATCH] smb3: add mount parm nosparse

To reduce risk of applications breaking that mount to servers
with only partial sparse file support, add optional mount parm
"nosparse" which disables setting files sparse (and thus
will return EOPNOTSUPP on certain fallocate operations).

Signed-off-by: Steve French <stfrench@microsoft.com>
---
 fs/cifs/cifs_debug.c | 3 ++-
 fs/cifs/cifsfs.c     | 2 ++
 fs/cifs/connect.c    | 1 +
 fs/cifs/fs_context.c | 4 ++++
 fs/cifs/fs_context.h | 2 ++
 5 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/fs/cifs/cifs_debug.c b/fs/cifs/cifs_debug.c
index 9d334816eac0..0effc4c95077 100644
--- a/fs/cifs/cifs_debug.c
+++ b/fs/cifs/cifs_debug.c
@@ -116,7 +116,8 @@ static void cifs_debug_tcon(struct seq_file *m, struct cifs_tcon *tcon)
 		tcon->ses->server->ops->dump_share_caps(m, tcon);
 	if (tcon->use_witness)
 		seq_puts(m, " Witness");
-
+	if (tcon->broken_sparse_sup)
+		seq_puts(m, " nosparse");
 	if (tcon->need_reconnect)
 		seq_puts(m, "\tDISCONNECTED ");
 	seq_putc(m, '\n');
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 2b1a1c029c75..f539a39d47f5 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -582,6 +582,8 @@ cifs_show_options(struct seq_file *s, struct dentry *root)
 		seq_puts(s, ",nocase");
 	if (tcon->nodelete)
 		seq_puts(s, ",nodelete");
+	if (cifs_sb->ctx->no_sparse)
+		seq_puts(s, ",nosparse");
 	if (tcon->local_lease)
 		seq_puts(s, ",locallease");
 	if (tcon->retry)
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 0b08693d1af8..1fd8d6a97d7c 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -2509,6 +2509,7 @@ cifs_get_tcon(struct cifs_ses *ses, struct smb3_fs_context *ctx)
 	 */
 	tcon->retry = ctx->retry;
 	tcon->nocase = ctx->nocase;
+	tcon->broken_sparse_sup = ctx->no_sparse;
 	if (ses->server->capabilities & SMB2_GLOBAL_CAP_DIRECTORY_LEASING)
 		tcon->nohandlecache = ctx->nohandlecache;
 	else
diff --git a/fs/cifs/fs_context.c b/fs/cifs/fs_context.c
index a92e9eec521f..ca1d6957a099 100644
--- a/fs/cifs/fs_context.c
+++ b/fs/cifs/fs_context.c
@@ -119,6 +119,7 @@ const struct fs_parameter_spec smb3_fs_parameters[] = {
 	fsparam_flag_no("persistenthandles", Opt_persistent),
 	fsparam_flag_no("resilienthandles", Opt_resilient),
 	fsparam_flag_no("tcpnodelay", Opt_tcp_nodelay),
+	fsparam_flag("nosparse", Opt_nosparse),
 	fsparam_flag("domainauto", Opt_domainauto),
 	fsparam_flag("rdma", Opt_rdma),
 	fsparam_flag("modesid", Opt_modesid),
@@ -943,6 +944,9 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
 	case Opt_nolease:
 		ctx->no_lease = 1;
 		break;
+	case Opt_nosparse:
+		ctx->no_sparse = 1;
+		break;
 	case Opt_nodelete:
 		ctx->nodelete = 1;
 		break;
diff --git a/fs/cifs/fs_context.h b/fs/cifs/fs_context.h
index e54090d9ef36..6576bb12f5f1 100644
--- a/fs/cifs/fs_context.h
+++ b/fs/cifs/fs_context.h
@@ -62,6 +62,7 @@ enum cifs_param {
 	Opt_noblocksend,
 	Opt_noautotune,
 	Opt_nolease,
+	Opt_nosparse,
 	Opt_hard,
 	Opt_soft,
 	Opt_perm,
@@ -222,6 +223,7 @@ struct smb3_fs_context {
 	bool noautotune:1;
 	bool nostrictsync:1; /* do not force expensive SMBflush on every sync */
 	bool no_lease:1;     /* disable requesting leases */
+	bool no_sparse:1;    /* do not attempt to set files sparse */
 	bool fsc:1;	/* enable fscache */
 	bool mfsymlinks:1; /* use Minshall+French Symlinks */
 	bool multiuser:1;
-- 
2.34.1