align data passed to write() on 32k boundaries

In donut, OTA installation often encounters the write() system call
doing short writes -- which is legal but unexpected -- or failing with
ENOSPC when plenty of space is available.  Passing aligned memory
buffers to write() appears to prevent (or at least reduce the
frequency) of these problems.  b/1833052 has been filed to look at the
underlying problem, but this change aligns buffers we use with write()
so we can OTA for now (or see if this problem still occurs).

minzip/Zip.c

@@ -12,6 +12,7 @@
 #include <stdint.h>     // for uintptr_t
 #include <stdlib.h>
 #include <sys/stat.h>   // for S_ISLNK()
+#include <sys/statfs.h>
 #include <unistd.h>
 
 #define LOG_TAG "minzip"
@@ -84,6 +85,12 @@ enum {
 };
 
 
+/* The maximum zipped file write size we will align. */
+#define WRITE_SIZE  32768
+/* The boundary on which we will align it. */
+#define WRITE_ALIGNMENT 32768
+
+
 /*
  * For debugging, dump the contents of a ZipEntry.
  */
@@ -770,17 +777,38 @@ bool mzReadZipEntry(const ZipArchive* pArchive, const ZipEntry* pEntry,
 }
 
 static bool writeProcessFunction(const unsigned char *data, int dataLen,
-        void *fd)
+                                 void *cookie)
 {
-    int zeroWrites = 0;
+    WriteInfo *wi = (WriteInfo*)cookie;
+
+    if (dataLen <= WRITE_SIZE) {
+        memcpy(wi->aligned_buffer, data, dataLen);
+        data = wi->aligned_buffer;
+    }
+
     ssize_t soFar = 0;
-    do {
-        ssize_t n = write((int)fd, data+soFar, dataLen-soFar);
-        if (n < 0) {
-            LOGE("Error writing %ld bytes from zip file: %s\n",
-                 dataLen-soFar, strerror(errno));
+    while (true) {
+        ssize_t n = write(wi->fd, data+soFar, dataLen-soFar);
+        if (n <= 0) {
+            LOGE("Error writing %ld bytes from zip file from %p: %s\n",
+                 dataLen-soFar, data+soFar, strerror(errno));
+            if (errno == ENOSPC) {
+                struct statfs sf;
+                if (statfs("/system", &sf) != 0) {
+                    LOGE("failed to statfs /system: %s\n", strerror(errno));
+                } else {
+                    LOGE("statfs said: %ld * %ld = %ld\n",
+                         (long)sf.f_bsize, (long)sf.f_bfree,
+                         (long)sf.f_bsize * (long)sf.f_bfree);
+                }
+            }
             return false;
         } else if (n > 0) {
+            if (n < dataLen-soFar) {
+                LOGE("short write: %d bytes of %d from %p\n",
+                     (int)n, (int)(dataLen-soFar),
+                     data+soFar);
+            }
             soFar += n;
             if (soFar == dataLen) return true;
             if (soFar > dataLen) {
@@ -788,23 +816,18 @@ static bool writeProcessFunction(const unsigned char *data, int dataLen,
                      soFar, dataLen);
                 return false;
             }
-            zeroWrites = 0;
-        } else {
-            ++zeroWrites;
         }
-    } while (zeroWrites < 5);
-    LOGE("too many consecutive zero-length writes\n");
-    return false;
+    }
 }
 
 /*
  * Uncompress "pEntry" in "pArchive" to "fd" at the current offset.
  */
 bool mzExtractZipEntryToFile(const ZipArchive *pArchive,
-    const ZipEntry *pEntry, int fd)
+    const ZipEntry *pEntry, WriteInfo *wi)
 {
     bool ret = mzProcessZipEntryContents(pArchive, pEntry, writeProcessFunction,
-            (void *)fd);
+                                         wi);
     if (!ret) {
         LOGE("Can't extract entry to file.\n");
         return false;
@@ -906,6 +929,11 @@ bool mzExtractRecursive(const ZipArchive *pArchive,
         return false;
     }
 
+    unsigned char* buffer = malloc(WRITE_SIZE+WRITE_ALIGNMENT);
+    WriteInfo wi;
+    wi.aligned_buffer = buffer + WRITE_ALIGNMENT -
+            ((long)buffer % WRITE_ALIGNMENT);
+
     unsigned int zipDirLen;
     char *zpath;
 
@@ -1086,7 +1114,8 @@ bool mzExtractRecursive(const ZipArchive *pArchive,
                     break;
                 }
 
-                bool ok = mzExtractZipEntryToFile(pArchive, pEntry, fd);
+                wi.fd = fd;
+                bool ok = mzExtractZipEntryToFile(pArchive, pEntry, &wi);
                 close(fd);
                 if (!ok) {
                     LOGE("Error extracting \"%s\"\n", targetFile);
@@ -1109,6 +1138,7 @@ bool mzExtractRecursive(const ZipArchive *pArchive,
 
     free(helper.buf);
     free(zpath);
+    free(buffer);
 
     return ok;
 }

minzip/Zip.h

@@ -55,6 +55,14 @@ typedef struct {
     size_t len;
 } UnterminatedString;
 
+/*
+ * The information we pass down to writeProcessFunction.
+ */
+typedef struct {
+    int fd;
+    unsigned char* aligned_buffer;
+} WriteInfo;
+
 /*
  * Open a Zip archive.
  *
@@ -166,7 +174,7 @@ bool mzIsZipEntryIntact(const ZipArchive *pArchive, const ZipEntry *pEntry);
  * Inflate and write an entry to a file.
  */
 bool mzExtractZipEntryToFile(const ZipArchive *pArchive,
-    const ZipEntry *pEntry, int fd);
+    const ZipEntry *pEntry, WriteInfo *wi);
 
 /*
  * Inflate all entries under zipDir to the directory specified by