[PATCH 06/11] netfs: Fix the trace displayed for the total overwrite of a streamed write

David Howells
2026-04-20T08:37:52Z

Change netfs_perform_write() to carry the trace value in a variable and
emit it later to make it easier to select the value displayed.

Fix the display of netfs_streaming_write_cont in the "folio_now_filled:"
section. It should only be set to that if we come from the section that
filled in a gap in an already streamed write (and would otherwise display
netfs_streaming_write_cont). If it came from the bit that just overwrites
the entire folio (which would ordinarily display netfs_whole_folio_modify),
make it display netfs_whole_folio_modify_filled instead.

Fixes: 1bfeb53e990b ("netfs: Fix streaming write being overwritten")
Closes: https://sashiko.dev/#/patchset/20260414082004.3756080-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Paulo Alcantara <pc@manguebit.org>
cc: Matthew Wilcox <willy@infradead.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
fs/netfs/buffered_write.c | 27 ++++++++++++++++-----------
include/trace/events/netfs.h | 1 +
2 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c
index 6399141b4f0a..de82eb6ed473 100644
--- a/fs/netfs/buffered_write.c
+++ b/fs/netfs/buffered_write.c
@@ -150,6 +150,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
}

do {
+ enum netfs_folio_trace trace;
struct netfs_folio *finfo;
struct netfs_group *group;
unsigned long long fpos;
@@ -223,7 +224,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
if (unlikely(copied == 0))
goto copy_failed;
netfs_set_group(folio, netfs_group);
- trace_netfs_folio(folio, netfs_folio_is_uptodate);
+ trace = netfs_folio_is_uptodate;
goto copied;
}

@@ -239,7 +240,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
folio_zero_segment(folio, offset + copied, flen);
__netfs_set_group(folio, netfs_group);
folio_mark_uptodate(folio);
- trace_netfs_folio(folio, netfs_modify_and_clear);
+ trace = netfs_modify_and_clear;
goto copied;
}

@@ -247,11 +248,13 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
if (!maybe_trouble && offset == 0 && part >= flen) {
copied = copy_folio_from_iter_atomic(folio, offset, part, iter);
if (likely(copied == part)) {
- if (finfo)
+ if (finfo) {
+ trace = netfs_whole_folio_modify_filled;
goto folio_now_filled;
+ }
__netfs_set_group(folio, netfs_group);
folio_mark_uptodate(folio);
- trace_netfs_folio(folio, netfs_whole_folio_modify);
+ trace = netfs_whole_folio_modify;
goto copied;
}
if (copied == 0)
@@ -273,7 +276,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
if (copied > finfo->dirty_len)
finfo->dirty_len = copied;
finfo->dirty_offset = 0;
- trace_netfs_folio(folio, netfs_whole_folio_modify_efault);
+ trace = netfs_whole_folio_modify_efault;
goto copied;
}

@@ -299,7 +302,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
if (unlikely(copied == 0))
goto copy_failed;
netfs_set_group(folio, netfs_group);
- trace_netfs_folio(folio, netfs_just_prefetch);
+ trace = netfs_just_prefetch;
goto copied;
}

@@ -313,7 +316,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
if (offset == 0 && copied == flen) {
__netfs_set_group(folio, netfs_group);
folio_mark_uptodate(folio);
- trace_netfs_folio(folio, netfs_streaming_filled_page);
+ trace = netfs_streaming_filled_page;
goto copied;
}

@@ -328,7 +331,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
finfo->dirty_len = copied;
folio_attach_private(folio, (void *)((unsigned long)finfo |
NETFS_FOLIO_INFO));
- trace_netfs_folio(folio, netfs_streaming_write);
+ trace = netfs_streaming_write;
goto copied;
}

@@ -341,9 +344,11 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
if (unlikely(copied == 0))
goto copy_failed;
finfo->dirty_len += copied;
- if (finfo->dirty_offset == 0 && finfo->dirty_len == flen)
+ if (finfo->dirty_offset == 0 && finfo->dirty_len == flen) {
+ trace = netfs_streaming_cont_filled_page;
goto folio_now_filled;
- trace_netfs_folio(folio, netfs_streaming_write_cont);
+ }
+ trace = netfs_streaming_write_cont;
goto copied;
}

@@ -364,8 +369,8 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
folio_detach_private(folio);
folio_mark_uptodate(folio);
kfree(finfo);
- trace_netfs_folio(folio, netfs_streaming_cont_filled_page);
copied:
+ trace_netfs_folio(folio, trace);
flush_dcache_folio(folio);

/* Update the inode size if we moved the EOF marker */
diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h
index ee7fea84f055..67f6d56c94ce 100644
--- a/include/trace/events/netfs.h
+++ b/include/trace/events/netfs.h
@@ -178,6 +178,7 @@
EM(netfs_just_prefetch, "mod-prefetch") \
EM(netfs_whole_folio_modify, "mod-whole-f") \
EM(netfs_whole_folio_modify_efault, "mod-whole-f!") \
+ EM(netfs_whole_folio_modify_filled, "mod-whole-f+") \
EM(netfs_modify_and_clear, "mod-n-clear") \
EM(netfs_streaming_write, "mod-streamw") \
EM(netfs_streaming_write_cont, "mod-streamw+") \