[PATCH][SMB3 client] update allocation size more accurately on write completion

[Steve French <smfrench@gmail.com>]

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Changes to allocation size are approximated for extending writes of
cached files until the server returns the actual value (on SMB3 close
or query info for example), but it was setting the estimated value for
number of blocks to larger than the file size even if the file is
likely sparse which breaks various xfstests (e.g. generic/129, 130,
221, 228).

When i_size and i_blocks are updated in write completion do not
increase allocation size more than what was written (rounded up to 512
bytes).

See attached.

This fixes the recent regression in various xfstests caused by the
xfstest change

commit b4396efc75aba5325f22690303857af4f63d128e
Author: Alexander Patrakov <patrakov@gmail.com>
Date:   Tue Dec 19 04:57:20 2023 +0800

    _require_sparse_files: rewrite as a direct test instead of a black list


-- 
Thanks,

Steve

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From ae33f1b691cc9fd6fc0dfe84981e5e8d5f0cd3d2 Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@microsoft.com>
Date: Thu, 22 Feb 2024 00:26:52 -0600
Subject: [PATCH] smb3: update allocation size more accurately on write
 completion

Changes to allocation size are approximated for extending writes of cached
files until the server returns the actual value (on SMB3 close or query info
for example), but it was setting the estimated value for number of blocks
to larger than the file size even if the file is likely sparse which
breaks various xfstests (e.g. generic/129, 130, 221, 228).

When i_size and i_blocks are updated in write completion do not increase
allocation size more than what was written (rounded up to 512 bytes).

Signed-off-by: Steve French <stfrench@microsoft.com>
---
 fs/smb/client/file.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/smb/client/file.c b/fs/smb/client/file.c
index 05e915162f05..6b2da368d52d 100644
--- a/fs/smb/client/file.c
+++ b/fs/smb/client/file.c
@@ -3095,8 +3095,15 @@ static int cifs_write_end(struct file *file, struct address_space *mapping,
 	if (rc > 0) {
 		spin_lock(&inode->i_lock);
 		if (pos > inode->i_size) {
+			loff_t additional_blocks = (512 - 1 + copied) >> 9;
+
 			i_size_write(inode, pos);
-			inode->i_blocks = (512 - 1 + pos) >> 9;
+			/*
+			 * Estimate new allocation size based on the amount written.
+			 * This will be updated from server on close (and on queryinfo)
+			 */
+			inode->i_blocks = min_t(blkcnt_t, (512 - 1 + pos) >> 9,
+						inode->i_blocks + additional_blocks);
 		}
 		spin_unlock(&inode->i_lock);
 	}
-- 
2.40.1