ash
53 lines
2.6 KiB
Diff
53 lines
2.6 KiB
Diff
From 2c5754649e08a664f3d43f7bc1df08f498bc1554 Mon Sep 17 00:00:00 2001
|
|
From: =?UTF-8?q?P=C3=A1draig=20Brady?= <P@draigBrady.com>
|
|
Date: Fri, 31 Oct 2025 15:37:55 +0000
|
|
Subject: [PATCH] copy: be more defensive/restrictive with posix_fadvise
|
|
|
|
* src/copy-file-data.c (copy_file_data): Only give the
|
|
POSIX_FADV_SEQUENTIAL hint when we _know_ we'll definitely
|
|
use a read/write loop to copy the data. Also only apply
|
|
the hint to the whole file, as we've seen OpenZFS at least
|
|
special case that.
|
|
(sparse_copy): Update stale comment.
|
|
---
|
|
src/copy-file-data.c | 17 +++++++++--------
|
|
1 file changed, 9 insertions(+), 8 deletions(-)
|
|
|
|
diff --git a/src/copy-file-data.c b/src/copy-file-data.c
|
|
index 8fd25fee9201eda7bd0a8caf01f02821a3390448..c46b7edc5228f5f1e9c398d8ad7ff20b6fa60fb6 100644
|
|
--- a/src/copy-file-data.c
|
|
+++ b/src/copy-file-data.c
|
|
@@ -105,8 +105,6 @@ is_CLONENOTSUP (int err)
|
|
If HOLE_SIZE, look for holes in the input; *HOLE_SIZE contains
|
|
the size of the current hole so far, and update *HOLE_SIZE
|
|
at end to be the size of the hole at the end of the copy.
|
|
- Set *TOTAL_N_READ to the number of bytes read; this counts
|
|
- the trailing hole, which has not yet been output.
|
|
Read and update *DEBUG as needed.
|
|
If successful, return the number of bytes copied,
|
|
otherwise diagnose the failure and return -1. */
|
|
@@ -542,14 +540,17 @@ copy_file_data (int ifd, struct stat const *ist, off_t ipos, char const *iname,
|
|
|| (x->sparse_mode == SPARSE_AUTO
|
|
&& scantype != PLAIN_SCANTYPE)));
|
|
|
|
- /* Don't bother calling fadvise for small copies, as it is not
|
|
- likely to help performance and might even hurt it.
|
|
- Note it's important to use a 0 length to indicate the whole file
|
|
+ /* If we _know_ we're going to read data sequentially into the process,
|
|
+ i.e., --reflink or --sparse are not in auto mode,
|
|
+ give that hint to the kernel so it can tune caching behavior.
|
|
+ Also we don't bother calling fadvise for small copies,
|
|
+ as it is not likely to help performance and might even hurt it.
|
|
+ Also we only apply this hint for the whole file (0 length)
|
|
as OpenZFS 2.2.2 at least will otherwise synchronously
|
|
(decompress and) populate the cache when given a specific length. */
|
|
- if (IO_BUFSIZE < ibytes)
|
|
- fdadvise (ifd, ipos, ibytes < OFF_T_MAX - ipos ? ibytes : 0,
|
|
- FADVISE_SEQUENTIAL);
|
|
+ if (ipos == 0 && ibytes == COUNT_MAX
|
|
+ && (x->reflink_mode != REFLINK_AUTO || x->sparse_mode != SPARSE_AUTO))
|
|
+ fdadvise (ifd, 0, 0, FADVISE_SEQUENTIAL);
|
|
|
|
/* If not making a sparse file, try to use a more-efficient
|
|
buffer size. */
|