From 9d87b08c5279b2f0769dc7a788a9d7296926b2a2 Mon Sep 17 00:00:00 2001
From: Luflosi <luflosi@luflosi.de>
Date: Wed, 26 Jan 2022 23:35:54 +0100
Subject: [PATCH 1/2] Fix logic error in file copy helper functions

If `errno` is `EAGAIN`, the second if statement is never true and if `errno` is not `EAGAIN`, the function returns immediately, not checking the second if statement.
This commit fixes this.
A logically equivalent change would have been to simply swap the two if statements but I find this version to be more readable.
---
 kitty/fast-file-copy.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kitty/fast-file-copy.c b/kitty/fast-file-copy.c
index dec635286..15f0257fe 100644
--- a/kitty/fast-file-copy.c
+++ b/kitty/fast-file-copy.c
@@ -60,9 +60,9 @@ copy_with_sendfile(int infd, int outfd, off_t in_pos, size_t len, FastFileCopyBu
         off_t r = in_pos;
         ssize_t n = sendfile(outfd, infd, &r, len);
         if (n < 0) {
-            if (errno != EAGAIN) return false;
+            if (errno == EAGAIN) continue;
             if (errno == ENOSYS || errno == EPERM) return copy_with_buffer(infd, outfd, in_pos, len, fcb);
-            continue;
+            return false;
         }
         if (n == 0) {
             // happens if input file is truncated
@@ -83,9 +83,9 @@ copy_with_file_range(int infd, int outfd, off_t in_pos, size_t len, FastFileCopy
         off64_t r = in_pos;
         ssize_t n = copy_file_range(infd, &r, outfd, NULL, len, 0);
         if (n < 0) {
-            if (errno != EAGAIN) return false;
+            if (errno == EAGAIN) continue;
             if (errno == ENOSYS || errno == EPERM) return copy_with_sendfile(infd, outfd, in_pos, len, fcb);
-            continue;
+            return false;
         }
         if (n == 0) {
             // happens if input file is truncated

From 4c78a50dcf98dbc66b5111a36d48a000baefd76f Mon Sep 17 00:00:00 2001
From: Luflosi <luflosi@luflosi.de>
Date: Wed, 26 Jan 2022 23:39:46 +0100
Subject: [PATCH 2/2] Add more copy_file_range() and sendfile() errno
 exceptions

On ZFS `copy_file_range()` and `sendfile()` fail for some reason, so add `EINVAL` to the list of error codes for which the code will fall back to a slower implementation.
While we are at it, add all the error codes from https://go.dev/src/internal/poll/copy_file_range_linux.go for different filesystems and older kernel versions to the list of error codes from `copy_file_range()`.
Without this, the cache defragmentation and the test testing it (`test_disk_cache`) fail with the error message "Failed to copy data to new disk cache file during defrag: Invalid argument" when the cache directory is stored on ZFS.
Perhaps this is caused by me running ZFS 2.1.2 on Linux 5.16.0, which is not a supported combination. This ZFS version is only "compatible with 3.10 - 5.15 kernels" according to the release notes. Or maybe it's just not implemented.
To reproduce the problem, execute `KITTY_CACHE_DIRECTORY=/path/to/zfs python3 test.py` with `KITTY_CACHE_DIRECTORY` pointing to a directory on ZFS.
---
 kitty/fast-file-copy.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/kitty/fast-file-copy.c b/kitty/fast-file-copy.c
index 15f0257fe..8c3e032df 100644
--- a/kitty/fast-file-copy.c
+++ b/kitty/fast-file-copy.c
@@ -61,7 +61,10 @@ copy_with_sendfile(int infd, int outfd, off_t in_pos, size_t len, FastFileCopyBu
         ssize_t n = sendfile(outfd, infd, &r, len);
         if (n < 0) {
             if (errno == EAGAIN) continue;
-            if (errno == ENOSYS || errno == EPERM) return copy_with_buffer(infd, outfd, in_pos, len, fcb);
+            if (errno == ENOSYS || // No kernel support
+                errno == EPERM  ||
+                errno == EINVAL)   // ZFS for some reason
+                return copy_with_buffer(infd, outfd, in_pos, len, fcb);
             return false;
         }
         if (n == 0) {
@@ -84,7 +87,13 @@ copy_with_file_range(int infd, int outfd, off_t in_pos, size_t len, FastFileCopy
         ssize_t n = copy_file_range(infd, &r, outfd, NULL, len, 0);
         if (n < 0) {
             if (errno == EAGAIN) continue;
-            if (errno == ENOSYS || errno == EPERM) return copy_with_sendfile(infd, outfd, in_pos, len, fcb);
+            if (errno == ENOSYS     || // Linux < 4.5
+                errno == EPERM      || // Possibly Docker
+                errno == EINVAL     || // ZFS for some reason
+                errno == EIO        || // CIFS
+                errno == EOPNOTSUPP || // NFS
+                errno == EXDEV)        // Prior to Linux 5.3, it was not possible to copy_file_range across file systems
+                return copy_with_sendfile(infd, outfd, in_pos, len, fcb);
             return false;
         }
         if (n == 0) {