afs: Skip checking chunkBytes sanity for RW files

[openafs.git] / src / afs / afs_dcache.c

diff --git a/src/afs/afs_dcache.c b/src/afs/afs_dcache.c
index 2f54bf7..ef32feb 100644 (file)
--- a/src/afs/afs_dcache.c
+++ b/src/afs/afs_dcache.c
@@ -1773,6 +1773,29 @@ IsDCacheSizeOK(struct dcache *adc, struct vcache *avc, afs_int32 chunk_bytes,
        return 1;
     }
 
+    if (!from_net && (adc->f.states & DRW)) {
+       /*
+        * The dcache data we're looking at is from our local cache (not from a
+        * fileserver), and it's for data in an RW volume. For cached RW data,
+        * there are some edge cases that can cause the below length checks to
+        * trigger false positives.
+        *
+        * For example: if the local client writes 4 bytes to a new file at
+        * offset 0, and then 4 bytes at offset 0x400000, the file will be
+        * 0x400004 bytes long, but the first dcache chunk will only contain 4
+        * bytes. If such a file is fetched from a fileserver, the first chunk
+        * will have a full chunk of data (most of it zeroes), but on the
+        * client that did the write, the sparse data will not appear in the
+        * dcache.
+        *
+        * Such false positives should only be possible with RW data, since
+        * non-RW data is never generated locally. So to avoid the false
+        * positives, assume the dcache length is OK for RW data if the dcache
+        * came from our local cache (and not directly from a fileserver).
+        */
+       return 1;
+    }
+
     if (file_length < chunk_start) {
        expected_bytes = 0;