]> wimlib.net Git - wimlib/blobdiff - src/write.c
Variable chunk size support (currently XPRESS only)
[wimlib] / src / write.c
index 6c97c79604823415a831f7a7fecc303195f1ec9d..8554d1ab573fc23af05533c2f9f1cde750e0914e 100644 (file)
 #  include <sys/uio.h> /* for `struct iovec' */
 #endif
 
-static int
-alloc_lzx_context(int write_resource_flags, struct wimlib_lzx_context **ctx_pp)
+/* Return true if the specified resource is compressed and the compressed data
+ * can be reused with the specified output parameters.  */
+static bool
+can_raw_copy(const struct wim_lookup_table_entry *lte,
+            int write_resource_flags, int out_ctype, u32 out_chunk_size)
 {
-       struct wimlib_lzx_params params;
-       params.size_of_this = sizeof(params);
-       if (write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_COMPRESS_SLOW)
-               params.algorithm = WIMLIB_LZX_ALGORITHM_SLOW;
-       else
-               params.algorithm = WIMLIB_LZX_ALGORITHM_FAST;
-       params.use_defaults = 1;
-       return wimlib_lzx_alloc_context(&params, ctx_pp);
+       return (out_ctype == wim_resource_compression_type(lte)
+               && out_chunk_size == wim_resource_chunk_size(lte)
+               && out_ctype != WIMLIB_COMPRESSION_TYPE_NONE);
+}
+
+
+/* Return true if the specified resource must be recompressed when the specified
+ * output parameters are used.  */
+static bool
+must_compress_stream(const struct wim_lookup_table_entry *lte,
+                    int write_resource_flags, int out_ctype, u32 out_chunk_size)
+{
+       return (out_ctype != WIMLIB_COMPRESSION_TYPE_NONE
+               && ((write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_RECOMPRESS)
+                   || !can_raw_copy(lte, write_resource_flags,
+                                    out_ctype, out_chunk_size)));
 }
 
 static unsigned
@@ -128,6 +139,7 @@ struct chunk_table {
 static int
 begin_wim_resource_chunk_tab(const struct wim_lookup_table_entry *lte,
                             struct filedes *out_fd,
+                            u32 out_chunk_size,
                             struct chunk_table **chunk_tab_ret,
                             int resource_flags)
 {
@@ -139,7 +151,7 @@ begin_wim_resource_chunk_tab(const struct wim_lookup_table_entry *lte,
        int ret;
 
        size = wim_resource_size(lte);
-       num_chunks = wim_resource_chunks(lte);
+       num_chunks = DIV_ROUND_UP(size, out_chunk_size);
        bytes_per_chunk_entry = (size > (1ULL << 32)) ? 8 : 4;
        alloc_size = sizeof(struct chunk_table) + num_chunks * sizeof(u64);
        chunk_tab = CALLOC(1, alloc_size);
@@ -286,6 +298,7 @@ finalize_and_check_sha1(SHA_CTX *sha_ctx, struct wim_lookup_table_entry *lte)
 
 struct write_resource_ctx {
        int out_ctype;
+       u32 out_chunk_size;
        struct wimlib_lzx_context *comp_ctx;
        struct chunk_table *chunk_tab;
        struct filedes *out_fd;
@@ -301,6 +314,10 @@ write_resource_cb(const void *chunk, size_t chunk_size, void *_ctx)
        const void *out_chunk;
        unsigned out_chunk_size;
        int ret;
+       void *compressed_chunk = NULL;
+       unsigned compressed_size;
+       bool compressed_chunk_malloced = false;
+       size_t stack_max = 32768;
 
        if (ctx->doing_sha)
                sha1_update(&ctx->sha_ctx, chunk, chunk_size);
@@ -308,11 +325,16 @@ write_resource_cb(const void *chunk, size_t chunk_size, void *_ctx)
        out_chunk = chunk;
        out_chunk_size = chunk_size;
        if (ctx->out_ctype != WIMLIB_COMPRESSION_TYPE_NONE) {
-               void *compressed_chunk;
-               unsigned compressed_size;
 
                /* Compress the chunk.  */
-               compressed_chunk = alloca(chunk_size);
+               if (chunk_size <= stack_max) {
+                       compressed_chunk = alloca(chunk_size);
+               } else {
+                       compressed_chunk = MALLOC(chunk_size);
+                       if (compressed_chunk == NULL)
+                               return WIMLIB_ERR_NOMEM;
+                       compressed_chunk_malloced = true;
+               }
 
                compressed_size = compress_chunk(chunk, chunk_size,
                                                 compressed_chunk,
@@ -348,11 +370,15 @@ write_resource_cb(const void *chunk, size_t chunk_size, void *_ctx)
        ret = full_write(ctx->out_fd, out_chunk, out_chunk_size);
        if (ret)
                goto error;
-       return 0;
+
+out_free_memory:
+       if (compressed_chunk_malloced)
+               FREE(compressed_chunk);
+       return ret;
 
 error:
        ERROR_WITH_ERRNO("Failed to write WIM resource chunk");
-       return ret;
+       goto out_free_memory;
 }
 
 /*
@@ -378,8 +404,6 @@ error:
  * @resource_flags:
  *     * WIMLIB_WRITE_RESOURCE_FLAG_RECOMPRESS to force data to be recompressed even
  *       if it could otherwise be copied directly from the input;
- *     * WIMLIB_WRITE_RESOURCE_FLAG_COMPRESS_SLOW to compress the data as much
- *       as possible;
  *     * WIMLIB_WRITE_RESOURCE_FLAG_PIPABLE if writing a resource for a pipable WIM
  *       (and the output file descriptor may be a pipe).
  *
@@ -396,12 +420,14 @@ error:
 int
 write_wim_resource(struct wim_lookup_table_entry *lte,
                   struct filedes *out_fd, int out_ctype,
+                  u32 out_chunk_size,
                   struct resource_entry *out_res_entry,
                   int resource_flags,
                   struct wimlib_lzx_context **comp_ctx)
 {
        struct write_resource_ctx write_ctx;
        off_t res_start_offset;
+       u32 in_chunk_size;
        u64 read_size;
        int ret;
 
@@ -417,11 +443,7 @@ write_wim_resource(struct wim_lookup_table_entry *lte,
         * desired other than no compression, we can simply copy the compressed
         * data without recompressing it.  This also means we must skip
         * calculating the SHA1, as we never will see the uncompressed data.  */
-       if (lte->resource_location == RESOURCE_IN_WIM &&
-           out_ctype == wim_resource_compression_type(lte) &&
-           out_ctype != WIMLIB_COMPRESSION_TYPE_NONE &&
-           !(resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_RECOMPRESS))
-       {
+       if (can_raw_copy(lte, resource_flags, out_ctype, out_chunk_size)) {
                /* Normally we can request a RAW_FULL read, but if we're reading
                 * from a pipable resource and writing a non-pipable resource or
                 * vice versa, then a RAW_CHUNKS read needs to be requested so
@@ -433,26 +455,27 @@ write_wim_resource(struct wim_lookup_table_entry *lte,
                        resource_flags |= WIMLIB_READ_RESOURCE_FLAG_RAW_FULL;
                else
                        resource_flags |= WIMLIB_READ_RESOURCE_FLAG_RAW_CHUNKS;
-               write_ctx.doing_sha = false;
                read_size = lte->resource_entry.size;
+               write_ctx.doing_sha = false;
        } else {
                write_ctx.doing_sha = true;
                sha1_init(&write_ctx.sha_ctx);
                read_size = lte->resource_entry.original_size;
        }
 
-
        /* If the output resource is to be compressed, initialize the chunk
         * table and set the function to use for chunk compression.  Exceptions:
         * no compression function is needed if doing a raw copy; also, no chunk
         * table is needed if doing a *full* (not per-chunk) raw copy.  */
        write_ctx.out_ctype = WIMLIB_COMPRESSION_TYPE_NONE;
+       write_ctx.out_chunk_size = out_chunk_size;
        write_ctx.chunk_tab = NULL;
        if (out_ctype != WIMLIB_COMPRESSION_TYPE_NONE) {
+               wimlib_assert(out_chunk_size > 0);
                if (!(resource_flags & WIMLIB_READ_RESOURCE_FLAG_RAW)) {
                        write_ctx.out_ctype = out_ctype;
                        if (out_ctype == WIMLIB_COMPRESSION_TYPE_LZX) {
-                               ret = alloc_lzx_context(resource_flags, comp_ctx);
+                               ret = wimlib_lzx_alloc_context(NULL, comp_ctx);
                                if (ret)
                                        goto out;
                        }
@@ -460,6 +483,7 @@ write_wim_resource(struct wim_lookup_table_entry *lte,
                }
                if (!(resource_flags & WIMLIB_READ_RESOURCE_FLAG_RAW_FULL)) {
                        ret = begin_wim_resource_chunk_tab(lte, out_fd,
+                                                          out_chunk_size,
                                                           &write_ctx.chunk_tab,
                                                           resource_flags);
                        if (ret)
@@ -484,8 +508,13 @@ write_wim_resource(struct wim_lookup_table_entry *lte,
        write_ctx.out_fd = out_fd;
        write_ctx.resource_flags = resource_flags;
 try_write_again:
+       if (write_ctx.out_ctype == WIMLIB_COMPRESSION_TYPE_NONE)
+               in_chunk_size = wim_resource_chunk_size(lte);
+       else
+               in_chunk_size = out_chunk_size;
        ret = read_resource_prefix(lte, read_size,
-                                  write_resource_cb, &write_ctx, resource_flags);
+                                  write_resource_cb,
+                                  in_chunk_size, &write_ctx, resource_flags);
        if (ret)
                goto out_free_chunk_tab;
 
@@ -568,6 +597,7 @@ int
 write_wim_resource_from_buffer(const void *buf, size_t buf_size,
                               int reshdr_flags, struct filedes *out_fd,
                               int out_ctype,
+                              u32 out_chunk_size,
                               struct resource_entry *out_res_entry,
                               u8 *hash_ret, int write_resource_flags,
                               struct wimlib_lzx_context **comp_ctx)
@@ -581,6 +611,7 @@ write_wim_resource_from_buffer(const void *buf, size_t buf_size,
        lte.attached_buffer              = (void*)buf;
        lte.resource_entry.original_size = buf_size;
        lte.resource_entry.flags         = reshdr_flags;
+       lte.compression_type             = WIMLIB_COMPRESSION_TYPE_NONE;
 
        if (write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PIPABLE) {
                sha1_buffer(buf, buf_size, lte.hash);
@@ -589,8 +620,8 @@ write_wim_resource_from_buffer(const void *buf, size_t buf_size,
                lte.unhashed = 1;
        }
 
-       ret = write_wim_resource(&lte, out_fd, out_ctype, out_res_entry,
-                                write_resource_flags, comp_ctx);
+       ret = write_wim_resource(&lte, out_fd, out_ctype, out_chunk_size,
+                                out_res_entry, write_resource_flags, comp_ctx);
        if (ret)
                return ret;
        if (hash_ret)
@@ -699,6 +730,7 @@ struct compressor_thread_params {
 
 struct message {
        struct wim_lookup_table_entry *lte;
+       u32 out_chunk_size;
        u8 *uncompressed_chunks[MAX_CHUNKS_PER_MSG];
        u8 *compressed_chunks[MAX_CHUNKS_PER_MSG];
        unsigned uncompressed_chunk_sizes[MAX_CHUNKS_PER_MSG];
@@ -817,6 +849,7 @@ do_write_streams_progress(struct write_streams_progress_data *progress_data,
 struct serial_write_stream_ctx {
        struct filedes *out_fd;
        int out_ctype;
+       u32 out_chunk_size;
        struct wimlib_lzx_context **comp_ctx;
        int write_resource_flags;
 };
@@ -826,7 +859,9 @@ serial_write_stream(struct wim_lookup_table_entry *lte, void *_ctx)
 {
        struct serial_write_stream_ctx *ctx = _ctx;
        return write_wim_resource(lte, ctx->out_fd,
-                                 ctx->out_ctype, &lte->output_resource_entry,
+                                 ctx->out_ctype,
+                                 ctx->out_chunk_size,
+                                 &lte->output_resource_entry,
                                  ctx->write_resource_flags,
                                  ctx->comp_ctx);
 }
@@ -926,6 +961,7 @@ do_write_stream_list_serial(struct list_head *stream_list,
                            struct wim_lookup_table *lookup_table,
                            struct filedes *out_fd,
                            int out_ctype,
+                           u32 out_chunk_size,
                            struct wimlib_lzx_context **comp_ctx,
                            int write_resource_flags,
                            struct write_streams_progress_data *progress_data)
@@ -933,6 +969,7 @@ do_write_stream_list_serial(struct list_head *stream_list,
        struct serial_write_stream_ctx ctx = {
                .out_fd = out_fd,
                .out_ctype = out_ctype,
+               .out_chunk_size = out_chunk_size,
                .write_resource_flags = write_resource_flags,
                .comp_ctx = comp_ctx,
        };
@@ -950,8 +987,6 @@ write_flags_to_resource_flags(int write_flags)
 
        if (write_flags & WIMLIB_WRITE_FLAG_RECOMPRESS)
                resource_flags |= WIMLIB_WRITE_RESOURCE_FLAG_RECOMPRESS;
-       if (write_flags & WIMLIB_WRITE_FLAG_COMPRESS_SLOW)
-               resource_flags |= WIMLIB_WRITE_RESOURCE_FLAG_COMPRESS_SLOW;
        if (write_flags & WIMLIB_WRITE_FLAG_PIPABLE)
                resource_flags |= WIMLIB_WRITE_RESOURCE_FLAG_PIPABLE;
        return resource_flags;
@@ -962,6 +997,7 @@ write_stream_list_serial(struct list_head *stream_list,
                         struct wim_lookup_table *lookup_table,
                         struct filedes *out_fd,
                         int out_ctype,
+                        u32 out_chunk_size,
                         struct wimlib_lzx_context **comp_ctx,
                         int write_resource_flags,
                         struct write_streams_progress_data *progress_data)
@@ -978,6 +1014,7 @@ write_stream_list_serial(struct list_head *stream_list,
                                           lookup_table,
                                           out_fd,
                                           out_ctype,
+                                          out_chunk_size,
                                           comp_ctx,
                                           write_resource_flags,
                                           progress_data);
@@ -1028,6 +1065,7 @@ struct main_writer_thread_ctx {
        struct filedes *out_fd;
        off_t res_start_offset;
        int out_ctype;
+       u32 out_chunk_size;
        struct wimlib_lzx_context **comp_ctx;
        int write_resource_flags;
        struct shared_queue *res_to_compress_queue;
@@ -1051,11 +1089,12 @@ struct main_writer_thread_ctx {
 };
 
 static int
-init_message(struct message *msg)
+init_message(struct message *msg, u32 out_chunk_size)
 {
+       msg->out_chunk_size = out_chunk_size;
        for (size_t i = 0; i < MAX_CHUNKS_PER_MSG; i++) {
-               msg->compressed_chunks[i] = MALLOC(WIM_CHUNK_SIZE);
-               msg->uncompressed_chunks[i] = MALLOC(WIM_CHUNK_SIZE);
+               msg->compressed_chunks[i] = MALLOC(out_chunk_size);
+               msg->uncompressed_chunks[i] = MALLOC(out_chunk_size);
                if (msg->compressed_chunks[i] == NULL ||
                    msg->uncompressed_chunks[i] == NULL)
                        return WIMLIB_ERR_NOMEM;
@@ -1083,7 +1122,7 @@ free_messages(struct message *msgs, size_t num_messages)
 }
 
 static struct message *
-allocate_messages(size_t num_messages)
+allocate_messages(size_t num_messages, u32 out_chunk_size)
 {
        struct message *msgs;
 
@@ -1091,7 +1130,7 @@ allocate_messages(size_t num_messages)
        if (!msgs)
                return NULL;
        for (size_t i = 0; i < num_messages; i++) {
-               if (init_message(&msgs[i])) {
+               if (init_message(&msgs[i], out_chunk_size)) {
                        free_messages(msgs, num_messages);
                        return NULL;
                }
@@ -1113,7 +1152,7 @@ main_writer_thread_init_ctx(struct main_writer_thread_ctx *ctx)
 {
        /* Pre-allocate all the buffers that will be needed to do the chunk
         * compression. */
-       ctx->msgs = allocate_messages(ctx->num_messages);
+       ctx->msgs = allocate_messages(ctx->num_messages, ctx->out_chunk_size);
        if (!ctx->msgs)
                return WIMLIB_ERR_NOMEM;
 
@@ -1199,6 +1238,7 @@ receive_compressed_chunks(struct main_writer_thread_ctx *ctx)
                         * it if needed.  */
                        ret = begin_wim_resource_chunk_tab(cur_lte,
                                                           ctx->out_fd,
+                                                          ctx->out_chunk_size,
                                                           &ctx->cur_chunk_tab,
                                                           ctx->write_resource_flags);
                        if (ret)
@@ -1249,6 +1289,7 @@ receive_compressed_chunks(struct main_writer_thread_ctx *ctx)
                                ret = write_wim_resource(cur_lte,
                                                         ctx->out_fd,
                                                         WIMLIB_COMPRESSION_TYPE_NONE,
+                                                        0,
                                                         &cur_lte->output_resource_entry,
                                                         ctx->write_resource_flags,
                                                         ctx->comp_ctx);
@@ -1290,6 +1331,7 @@ receive_compressed_chunks(struct main_writer_thread_ctx *ctx)
                                                                  ctx->lookup_table,
                                                                  ctx->out_fd,
                                                                  ctx->out_ctype,
+                                                                 ctx->out_chunk_size,
                                                                  ctx->comp_ctx,
                                                                  ctx->write_resource_flags,
                                                                  ctx->progress_data);
@@ -1389,6 +1431,7 @@ main_writer_thread_finish(void *_ctx)
                                           ctx->lookup_table,
                                           ctx->out_fd,
                                           ctx->out_ctype,
+                                          ctx->out_chunk_size,
                                           ctx->comp_ctx,
                                           ctx->write_resource_flags,
                                           ctx->progress_data);
@@ -1406,12 +1449,14 @@ submit_stream_for_compression(struct wim_lookup_table_entry *lte,
         * when @lte is already hashed. */
        sha1_init(&ctx->next_sha_ctx);
        ctx->next_chunk = 0;
-       ctx->next_num_chunks = wim_resource_chunks(lte);
+       ctx->next_num_chunks = DIV_ROUND_UP(wim_resource_size(lte),
+                                           ctx->out_chunk_size);
        ctx->next_lte = lte;
        INIT_LIST_HEAD(&lte->msg_list);
        list_add_tail(&lte->being_compressed_list, &ctx->outstanding_streams);
        ret = read_resource_prefix(lte, wim_resource_size(lte),
-                                  main_writer_thread_cb, ctx, 0);
+                                  main_writer_thread_cb,
+                                  ctx->out_chunk_size, ctx, 0);
        if (ret)
                return ret;
        wimlib_assert(ctx->next_chunk == ctx->next_num_chunks);
@@ -1425,10 +1470,8 @@ main_thread_process_next_stream(struct wim_lookup_table_entry *lte, void *_ctx)
        int ret;
 
        if (wim_resource_size(lte) < 1000 ||
-           ctx->out_ctype == WIMLIB_COMPRESSION_TYPE_NONE ||
-           (lte->resource_location == RESOURCE_IN_WIM &&
-            !(ctx->write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_RECOMPRESS) &&
-            lte->wim->compression_type == ctx->out_ctype))
+           !must_compress_stream(lte, ctx->write_resource_flags,
+                                 ctx->out_ctype, ctx->out_chunk_size))
        {
                /* Stream is too small or isn't being compressed.  Process it by
                 * the main thread when we have a chance.  We can't necessarily
@@ -1460,15 +1503,15 @@ get_default_num_threads(void)
  * create the number of threads requested.
  *
  * High level description of the algorithm for writing compressed streams in
- * parallel:  We perform compression on chunks of size WIM_CHUNK_SIZE bytes
- * rather than on full files.  The currently executing thread becomes the main
- * thread and is entirely in charge of reading the data to compress (which may
- * be in any location understood by the resource code--- such as in an external
- * file being captured, or in another WIM file from which an image is being
- * exported) and actually writing the compressed data to the output file.
- * Additional threads are "compressor threads" and all execute the
- * compressor_thread_proc, where they repeatedly retrieve buffers of data from
- * the main thread, compress them, and hand them back to the main thread.
+ * parallel:  We perform compression on chunks rather than on full files.  The
+ * currently executing thread becomes the main thread and is entirely in charge
+ * of reading the data to compress (which may be in any location understood by
+ * the resource code--- such as in an external file being captured, or in
+ * another WIM file from which an image is being exported) and actually writing
+ * the compressed data to the output file.  Additional threads are "compressor
+ * threads" and all execute the compressor_thread_proc, where they repeatedly
+ * retrieve buffers of data from the main thread, compress them, and hand them
+ * back to the main thread.
  *
  * Certain streams, such as streams that do not need to be compressed (e.g.
  * input compression type same as output compression type) or streams of very
@@ -1485,6 +1528,7 @@ write_stream_list_parallel(struct list_head *stream_list,
                           struct wim_lookup_table *lookup_table,
                           struct filedes *out_fd,
                           int out_ctype,
+                          u32 out_chunk_size,
                           struct wimlib_lzx_context **comp_ctx,
                           int write_resource_flags,
                           struct write_streams_progress_data *progress_data,
@@ -1540,8 +1584,7 @@ write_stream_list_parallel(struct list_head *stream_list,
                params[i].compressed_res_queue = &compressed_res_queue;
                params[i].out_ctype = out_ctype;
                if (out_ctype == WIMLIB_COMPRESSION_TYPE_LZX) {
-                       ret = alloc_lzx_context(write_resource_flags,
-                                               &params[i].comp_ctx);
+                       ret = wimlib_lzx_alloc_context(NULL, &params[i].comp_ctx);
                        if (ret)
                                goto out_free_params;
                }
@@ -1577,6 +1620,7 @@ write_stream_list_parallel(struct list_head *stream_list,
        ctx.lookup_table          = lookup_table;
        ctx.out_fd                = out_fd;
        ctx.out_ctype             = out_ctype;
+       ctx.out_chunk_size        = out_chunk_size;
        ctx.comp_ctx              = comp_ctx;
        ctx.res_to_compress_queue = &res_to_compress_queue;
        ctx.compressed_res_queue  = &compressed_res_queue;
@@ -1630,6 +1674,7 @@ out_serial_quiet:
                                        lookup_table,
                                        out_fd,
                                        out_ctype,
+                                       out_chunk_size,
                                        comp_ctx,
                                        write_resource_flags,
                                        progress_data);
@@ -1645,6 +1690,7 @@ static int
 write_stream_list(struct list_head *stream_list,
                  struct wim_lookup_table *lookup_table,
                  struct filedes *out_fd, int out_ctype,
+                 u32 out_chunk_size,
                  struct wimlib_lzx_context **comp_ctx,
                  int write_flags,
                  unsigned num_threads, wimlib_progress_func_t progress_func)
@@ -1680,12 +1726,9 @@ write_stream_list(struct list_head *stream_list,
        list_for_each_entry(lte, stream_list, write_streams_list) {
                num_streams++;
                total_bytes += wim_resource_size(lte);
-               if (out_ctype != WIMLIB_COMPRESSION_TYPE_NONE
-                      && (wim_resource_compression_type(lte) != out_ctype ||
-                          (write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_RECOMPRESS)))
-               {
+               if (must_compress_stream(lte, write_resource_flags,
+                                        out_ctype, out_chunk_size))
                        total_compression_bytes += wim_resource_size(lte);
-               }
                if (lte->resource_location == RESOURCE_IN_WIM) {
                        if (prev_wim_part != lte->wim) {
                                prev_wim_part = lte->wim;
@@ -1715,6 +1758,7 @@ write_stream_list(struct list_head *stream_list,
                                                 lookup_table,
                                                 out_fd,
                                                 out_ctype,
+                                                out_chunk_size,
                                                 comp_ctx,
                                                 write_resource_flags,
                                                 &progress_data,
@@ -1725,6 +1769,7 @@ write_stream_list(struct list_head *stream_list,
                                               lookup_table,
                                               out_fd,
                                               out_ctype,
+                                              out_chunk_size,
                                               comp_ctx,
                                               write_resource_flags,
                                               &progress_data);
@@ -2047,7 +2092,8 @@ write_wim_streams(WIMStruct *wim, int image, int write_flags,
        return write_stream_list(stream_list,
                                 wim->lookup_table,
                                 &wim->out_fd,
-                                wim->compression_type,
+                                wim->out_compression_type,
+                                wim->out_chunk_size,
                                 &wim->lzx_context,
                                 write_flags,
                                 num_threads,
@@ -2107,7 +2153,8 @@ write_wim_metadata_resources(WIMStruct *wim, int image, int write_flags,
                              "metadata resource.", i);
                        ret = write_wim_resource(imd->metadata_lte,
                                                 &wim->out_fd,
-                                                wim->compression_type,
+                                                wim->out_compression_type,
+                                                wim->out_chunk_size,
                                                 &imd->metadata_lte->output_resource_entry,
                                                 write_resource_flags,
                                                 &wim->lzx_context);
@@ -2140,10 +2187,12 @@ close_wim_writable(WIMStruct *wim, int write_flags)
 {
        int ret = 0;
 
-       if (!(write_flags & WIMLIB_WRITE_FLAG_FILE_DESCRIPTOR))
+       if (!(write_flags & WIMLIB_WRITE_FLAG_FILE_DESCRIPTOR)) {
+               DEBUG("Closing WIM file.");
                if (filedes_valid(&wim->out_fd))
                        if (filedes_close(&wim->out_fd))
                                ret = WIMLIB_ERR_WRITE;
+       }
        filedes_invalidate(&wim->out_fd);
        return ret;
 }
@@ -2206,6 +2255,8 @@ finish_write(WIMStruct *wim, int image, int write_flags,
        off_t new_lookup_table_end;
        u64 xml_totalbytes;
 
+       DEBUG("image=%d, write_flags=%08x", image, write_flags);
+
        write_resource_flags = write_flags_to_resource_flags(write_flags);
 
        /* In the WIM header, there is room for the resource entry for a
@@ -2280,6 +2331,7 @@ finish_write(WIMStruct *wim, int image, int write_flags,
        hdr_offset = 0;
        if (write_flags & WIMLIB_WRITE_FLAG_HEADER_AT_END)
                hdr_offset = wim->out_fd.offset;
+       DEBUG("Writing new header @ %"PRIu64".", hdr_offset);
        ret = write_wim_header_at_offset(&wim->hdr, &wim->out_fd, hdr_offset);
        if (ret)
                return ret;
@@ -2291,6 +2343,7 @@ finish_write(WIMStruct *wim, int image, int write_flags,
         * operation has been written to disk, but the new file data has not.
         */
        if (write_flags & WIMLIB_WRITE_FLAG_FSYNC) {
+               DEBUG("Syncing WIM file.");
                if (fsync(wim->out_fd.fd)) {
                        ERROR_WITH_ERRNO("Error syncing data to WIM file");
                        return WIMLIB_ERR_WRITE;
@@ -2584,6 +2637,13 @@ write_wim_part(WIMStruct *wim,
        wim->hdr.part_number = part_number;
        wim->hdr.total_parts = total_parts;
 
+       /* Set compression type if different.  */
+       if (wim->compression_type != wim->out_compression_type)
+               wim->hdr.flags = get_wim_hdr_cflags(wim->out_compression_type);
+
+       /* Set chunk size if different.  */
+       wim->hdr.chunk_size = wim->out_chunk_size;
+
        /* Use GUID if specified; otherwise generate a new one.  */
        if (guid)
                memcpy(wim->hdr.guid, guid, WIMLIB_GUID_LEN);
@@ -2687,6 +2747,7 @@ write_wim_part(WIMStruct *wim,
 out_restore_hdr:
        memcpy(&wim->hdr, &hdr_save, sizeof(struct wim_header));
        (void)close_wim_writable(wim, write_flags);
+       DEBUG("ret=%d", ret);
        return ret;
 }
 
@@ -2935,6 +2996,7 @@ overwrite_wim_inplace(WIMStruct *wim, int write_flags,
                                wim->lookup_table,
                                &wim->out_fd,
                                wim->compression_type,
+                               wim->chunk_size,
                                &wim->lzx_context,
                                write_flags,
                                num_threads,
@@ -3056,7 +3118,9 @@ wimlib_overwrite(WIMStruct *wim, int write_flags,
        if ((!wim->deletion_occurred || (write_flags & WIMLIB_WRITE_FLAG_SOFT_DELETE))
            && !(write_flags & (WIMLIB_WRITE_FLAG_REBUILD |
                                WIMLIB_WRITE_FLAG_PIPABLE))
-           && !(wim_is_pipable(wim)))
+           && !(wim_is_pipable(wim))
+           && wim->compression_type == wim->out_compression_type
+           && wim->chunk_size == wim->out_chunk_size)
        {
                ret = overwrite_wim_inplace(wim, write_flags, num_threads,
                                            progress_func);