From: Huiwen He <hehuiwen@kylinos.cn>
Date: Fri, 3 Jul 2026 05:32:57 +0000 (+0800)
Subject: smb/client: reduce fallocate zero buffer allocation
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=9e4ec3be67af41ab859302d7109b34976efd9258;p=thirdparty%2Fkernel%2Flinux.git

smb/client: reduce fallocate zero buffer allocation

The fallocate emulation allocates a 1 MiB zero-filled buffer even
though each SMB2_write request is limited to SMB2_MAX_BUFFER_SIZE,
which is 64 KiB. A high-order 1 MiB allocation is more likely to
fail on a fragmented system.

Allocate only the smaller of the requested range and SMB2_MAX_BUFFER_SIZE,
and reuse that zero-filled buffer for every write request. Also reject
a successful write that makes no progress to avoid looping indefinitely.

This reduces the contiguous allocation required by fallocate emulation
without changing the written data or range semantics.

Signed-off-by: Huiwen He <hehuiwen@kylinos.cn>
Reviewed-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
Signed-off-by: Steve French <stfrench@microsoft.com>
---

diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index ddb28464ff81..ce607915a483 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -3573,7 +3573,7 @@ static int smb3_simple_fallocate_write_range(unsigned int xid,
 					     char *buf)
 {
 	struct cifs_io_parms io_parms = {0};
-	int nbytes;
+	unsigned int nbytes;
 	int rc = 0;
 	struct kvec iov[2];
 
@@ -3594,9 +3594,10 @@ static int smb3_simple_fallocate_write_range(unsigned int xid,
 		rc = SMB2_write(xid, &io_parms, &nbytes, iov, 1);
 		if (rc)
 			break;
+		if (!nbytes)
+			return -EIO;
 		if (nbytes > len)
 			return -EINVAL;
-		buf += nbytes;
 		off += nbytes;
 		len -= nbytes;
 	}
@@ -3626,7 +3627,7 @@ static int smb3_simple_fallocate_range(unsigned int xid,
 	if (rc)
 		goto out;
 
-	buf = kvzalloc(1024 * 1024, GFP_KERNEL);
+	buf = kvzalloc(min_t(loff_t, len, SMB2_MAX_BUFFER_SIZE), GFP_KERNEL);
 	if (buf == NULL) {
 		rc = -ENOMEM;
 		goto out;