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Date:   Wed, 6 Dec 2023 18:12:03 +0300
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Subject: [PATCH 07/16] fs/ntfs3: Fix multithreaded stress test
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From:   Konstantin Komarovc <almaz.alexandrovich@paragon-software.com>
To:     <ntfs3@lists.linux.dev>
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Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
---
  fs/ntfs3/attrib.c | 21 ++++++++++++++-------
  1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/fs/ntfs3/attrib.c b/fs/ntfs3/attrib.c
index 63f70259edc0..4b78b669a3bd 100644
--- a/fs/ntfs3/attrib.c
+++ b/fs/ntfs3/attrib.c
@@ -886,7 +886,7 @@ int attr_data_get_block(struct ntfs_inode *ni, CLST 
vcn, CLST clen, CLST *lcn,
      struct runs_tree *run = &ni->file.run;
      struct ntfs_sb_info *sbi;
      u8 cluster_bits;
-    struct ATTRIB *attr = NULL, *attr_b;
+    struct ATTRIB *attr, *attr_b;
      struct ATTR_LIST_ENTRY *le, *le_b;
      struct mft_inode *mi, *mi_b;
      CLST hint, svcn, to_alloc, evcn1, next_svcn, asize, end, vcn0, alen;
@@ -904,12 +904,8 @@ int attr_data_get_block(struct ntfs_inode *ni, CLST 
vcn, CLST clen, CLST *lcn,
          *len = 0;
      up_read(&ni->file.run_lock);

-    if (*len) {
-        if (*lcn != SPARSE_LCN || !new)
-            return 0; /* Fast normal way without allocation. */
-        else if (clen > *len)
-            clen = *len;
-    }
+    if (*len && (*lcn != SPARSE_LCN || !new))
+        return 0; /* Fast normal way without allocation. */

      /* No cluster in cache or we need to allocate cluster in hole. */
      sbi = ni->mi.sbi;
@@ -918,6 +914,17 @@ int attr_data_get_block(struct ntfs_inode *ni, CLST 
vcn, CLST clen, CLST *lcn,
      ni_lock(ni);
      down_write(&ni->file.run_lock);

+    /* Repeat the code above (under write lock). */
+    if (!run_lookup_entry(run, vcn, lcn, len, NULL))
+        *len = 0;
+
+    if (*len) {
+        if (*lcn != SPARSE_LCN || !new)
+            goto out; /* normal way without allocation. */
+        if (clen > *len)
+            clen = *len;
+    }
+
      le_b = NULL;
      attr_b = ni_find_attr(ni, NULL, &le_b, ATTR_DATA, NULL, 0, NULL, 
&mi_b);
      if (!attr_b) {
-- 
2.34.1