linux-kernel - [PATCH 4.9 070/153] ext4: trim allocation requests to group size

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Date:   Fri, 10 Mar 2017 10:08:23 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Jan Kara <jack@...e.cz>, Theodore Tso <tytso@....edu>
Subject: [PATCH 4.9 070/153] ext4: trim allocation requests to group size

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jan Kara <jack@...e.cz>

commit cd648b8a8fd5071d232242d5ee7ee3c0815776af upstream.

If filesystem groups are artifically small (using parameter -g to
mkfs.ext4), ext4_mb_normalize_request() can result in a request that is
larger than a block group. Trim the request size to not confuse
allocation code.

Reported-by: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Signed-off-by: Jan Kara <jack@...e.cz>
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/ext4/mballoc.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3123,6 +3123,13 @@ ext4_mb_normalize_request(struct ext4_al
 	if (ar->pright && start + size - 1 >= ar->lright)
 		size -= start + size - ar->lright;

+	/*
+	 * Trim allocation request for filesystems with artificially small
+	 * groups.
+	 */
+	if (size > EXT4_BLOCKS_PER_GROUP(ac->ac_sb))
+		size = EXT4_BLOCKS_PER_GROUP(ac->ac_sb);
+
 	end = start + size;

 	/* check we don't cross already preallocated blocks */