linux-kernel - [PATCH 2/2] fs/ntfs3: Check possible errors in run

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Message-ID: <1e532f1e-1ba5-11a8-8cb1-100b5c3a0f3b@paragon-software.com>
Date:   Wed, 6 Jul 2022 20:33:12 +0300
From:   Konstantin Komarov <almaz.alexandrovich@...agon-software.com>
To:     <ntfs3@...ts.linux.dev>
CC:     <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>
Subject: [PATCH 2/2] fs/ntfs3: Check possible errors in run_pack in advance

Checking in advance speeds things up in some cases.

Signed-off-by: Konstantin Komarov <almaz.alexandrovich@...agon-software.com>
---
  fs/ntfs3/run.c | 39 ++++++++++++++++++++++-----------------
  1 file changed, 22 insertions(+), 17 deletions(-)

diff --git a/fs/ntfs3/run.c b/fs/ntfs3/run.c
index 95fb9d739706..e4bd46b02531 100644
--- a/fs/ntfs3/run.c
+++ b/fs/ntfs3/run.c
@@ -821,26 +821,36 @@ int run_pack(const struct runs_tree *run, CLST svcn, CLST len, u8 *run_buf,
  	CLST next_vcn, vcn, lcn;
  	CLST prev_lcn = 0;
  	CLST evcn1 = svcn + len;
+	const struct ntfs_run *r, *r_end;
  	int packed_size = 0;
  	size_t i;
-	bool ok;
  	s64 dlcn;
  	int offset_size, size_size, tmp;
  
-	next_vcn = vcn = svcn;
-
  	*packed_vcns = 0;
  
  	if (!len)
  		goto out;
  
-	ok = run_lookup_entry(run, vcn, &lcn, &len, &i);
+	/* Check all required entries [svcn, encv1) available. */
+	if (!run_lookup(run, svcn, &i))
+		return -ENOENT;
  
-	if (!ok)
-		goto error;
+	r_end = run->runs + run->count;
+	r = run->runs + i;
  
-	if (next_vcn != vcn)
-		goto error;
+	for (next_vcn = r->vcn + r->len; next_vcn < evcn1;
+	     next_vcn = r->vcn + r->len) {
+		if (++r >= r_end || r->vcn != next_vcn)
+			return -ENOENT;
+	}
+
+	/* Repeat cycle above and pack runs. Assume no errors. */
+	r = run->runs + i;
+	len = svcn - r->vcn;
+	vcn = svcn;
+	lcn = r->lcn == SPARSE_LCN ? SPARSE_LCN : (r->lcn + len);
+	len = r->len - len;
  
  	for (;;) {
  		next_vcn = vcn + len;
@@ -889,12 +899,10 @@ int run_pack(const struct runs_tree *run, CLST svcn, CLST len, u8 *run_buf,
  		if (packed_size + 1 >= run_buf_size || next_vcn >= evcn1)
  			goto out;
  
-		ok = run_get_entry(run, ++i, &vcn, &lcn, &len);
-		if (!ok)
-			goto error;
-
-		if (next_vcn != vcn)
-			goto error;
+		r += 1;
+		vcn = r->vcn;
+		lcn = r->lcn;
+		len = r->len;
  	}
  
  out:
@@ -903,9 +911,6 @@ int run_pack(const struct runs_tree *run, CLST svcn, CLST len, u8 *run_buf,
  		run_buf[0] = 0;
  
  	return packed_size + 1;
-
-error:
-	return -EOPNOTSUPP;
  }
  
  /*
-- 
2.37.0