linux-kernel - [PATCH 32/43] mmap: Clean up mmap

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Date:   Tue, 29 Nov 2022 16:44:34 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
CC:     Liam Howlett <liam.howlett@...cle.com>,
        Li Zetao <lizetao1@...wei.com>,
        Liam Howlett <liam.howlett@...cle.com>
Subject: [PATCH 32/43] mmap: Clean up mmap_region() unrolling

From: "Liam R. Howlett" <Liam.Howlett@...cle.com>

Move logic of unrolling to the error path as apposed to duplicating it
within the function body.  This reduces the potential of missing an
update to one path when making changes.

Cc: Li Zetao <lizetao1@...wei.com>
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 mm/mmap.c | 45 ++++++++++++++++++---------------------------
 1 file changed, 18 insertions(+), 27 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 6b05e1dbf705..af611f805776 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2660,12 +2660,11 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 		 * Expansion is handled above, merging is handled below.
 		 * Drivers should not alter the address of the VMA.
 		 */
-		if (WARN_ON((addr != vma->vm_start))) {
-			error = -EINVAL;
+		error = -EINVAL;
+		if (WARN_ON((addr != vma->vm_start)))
 			goto close_and_free_vma;
-		}
-		vma_iter_set(&vmi, addr);
 
+		vma_iter_set(&vmi, addr);
 		/*
 		 * If vm_flags changed after call_mmap(), we should try merge
 		 * vma again as we may succeed this time.
@@ -2702,25 +2701,13 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 	}
 
 	/* Allow architectures to sanity-check the vm_flags */
-	if (!arch_validate_flags(vma->vm_flags)) {
-		error = -EINVAL;
-		if (file)
-			goto close_and_free_vma;
-		else if (vma->vm_file)
-			goto unmap_and_free_vma;
-		else
-			goto free_vma;
-	}
+	error = -EINVAL;
+	if (!arch_validate_flags(vma->vm_flags))
+		goto close_and_free_vma;
 
-	if (vma_iter_prealloc(&vmi, vma)) {
-		error = -ENOMEM;
-		if (file)
-			goto close_and_free_vma;
-		else if (vma->vm_file)
-			goto unmap_and_free_vma;
-		else
-			goto free_vma;
-	}
+	error = -ENOMEM;
+	if (vma_iter_prealloc(&vmi, vma))
+		goto close_and_free_vma;
 
 	if (vma->vm_file)
 		i_mmap_lock_write(vma->vm_file->f_mapping);
@@ -2779,14 +2766,18 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 	return addr;
 
 close_and_free_vma:
-	if (vma->vm_ops && vma->vm_ops->close)
+	if (file && vma->vm_ops && vma->vm_ops->close)
 		vma->vm_ops->close(vma);
+
+	if (file || vma->vm_file) {
 unmap_and_free_vma:
-	fput(vma->vm_file);
-	vma->vm_file = NULL;
+		fput(vma->vm_file);
+		vma->vm_file = NULL;
 
-	/* Undo any partial mapping done by a device driver. */
-	unmap_region(mm, &mm->mm_mt, vma, prev, next, vma->vm_start, vma->vm_end);
+		/* Undo any partial mapping done by a device driver. */
+		unmap_region(mm, &mm->mm_mt, vma, prev, next, vma->vm_start,
+			     vma->vm_end);
+	}
 	if (file && (vm_flags & VM_SHARED))
 		mapping_unmap_writable(file->f_mapping);
 free_vma:
-- 
2.35.1