On Tue, Jan 26, 2021 at 7:29 AM Pavel Begunkov [off-list ref] wrote:

On 22/12/2020 02:10, Noah Goldstein wrote:

quoted

On Sun, Dec 20, 2020 at 03:18:05PM +0000, Pavel Begunkov wrote:

quoted

On 20/12/2020 06:50, noah wrote:> From: noah [off-list ref]

quoted

This patch makes it so that specify a file descriptor value of -2 will
skip updating the corresponding fixed file index.

This will allow for users to reduce the number of syscalls necessary
to update a sparse file range when using the fixed file option.

Answering the github thread -- it's indeed a simple change, I had it the
same day you posted the issue. See below it's a bit cleaner. However, I
want to first review "io_uring: buffer registration enhancements", and
if it's good, for easier merging/etc I'd rather prefer to let it go
first (even if partially).

Noah, want to give it a try? I've just sent a prep patch, with it you
can implement it cleaner with one continue.

 Absolutely. Will get on it ASAP.

quoted

quoted

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 941fe9b64fd9..b3ae9d5da17e 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c

@@ -7847,9 +7847,8 @@ static int __io_sqe_files_update(struct io_ring_ctx *ctx,
     if (IS_ERR(ref_node))
             return PTR_ERR(ref_node);

-    done = 0;
     fds = u64_to_user_ptr(up->fds);
-    while (nr_args) {
+    for (done = 0; done < nr_args; done++) {
             struct fixed_file_table *table;
             unsigned index;

@@ -7858,7 +7857,10 @@ static int __io_sqe_files_update(struct io_ring_ctx *ctx,
                     err = -EFAULT;
                     break;
             }
-            i = array_index_nospec(up->offset, ctx->nr_user_files);
+            if (fd == IORING_REGISTER_FILES_SKIP)
+                    continue;
+
+            i = array_index_nospec(up->offset + done, ctx->nr_user_files);
             table = &ctx->file_data->table[i >> IORING_FILE_TABLE_SHIFT];
             index = i & IORING_FILE_TABLE_MASK;
             if (table->files[index]) {

@@ -7896,9 +7898,6 @@ static int __io_sqe_files_update(struct io_ring_ctx *ctx,
                             break;
                     }
             }
-            nr_args--;
-            done++;
-            up->offset++;
     }

     if (needs_switch) {

--
Pavel Begunkov