From dd05add7b2b6004c5fa3a1f276f56d8668f86b65 Mon Sep 17 00:00:00 2001 From: Paulo Alcantara Date: Sat, 26 Sep 2026 19:20:30 -0300 Subject: netfs: zero the tail of a short DIO/unbuffered read The buffered read collector zero-fills the tail of a short read that stops below the inode's i_size (netfs_clear_unread()), so a read that races an extending write still returns the expected number of bytes. The non-buffered collector path does no such thing: it just records how much was transferred. Add the same zero-fill for the non-buffered case, gated on NETFS_SREQ_CLEAR_TAIL: a subreq's source sets that flag when a short result from it is known to be safe to treat as a hole, as opposed to NETFS_SREQ_HIT_EOF, which means the read genuinely ran off the end of the file and should be reported short as-is. Only CLEAR_TAIL should zero-fill here; a real EOF must stay a real short read. No source currently sets CLEAR_TAIL on an unbuffered/DIO subrequest, so this is inert on its own -- a following change teaches cifs to set it in the one case that needs it. Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item") Reviewed-by: David Howells Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara Cc: Christian Brauner Cc: Matthew Wilcox Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: stable@vger.kernel.org --- samples/ftrace/sample-trace-array.h | 84 +++++++++++++++++++++++++++++++++++++ 1 file changed, 84 insertions(+) create mode 100644 samples/ftrace/sample-trace-array.h (limited to 'samples/ftrace/sample-trace-array.h') diff --git a/samples/ftrace/sample-trace-array.h b/samples/ftrace/sample-trace-array.h new file mode 100644 index 000000000..6f8962428 --- /dev/null +++ b/samples/ftrace/sample-trace-array.h @@ -0,0 +1,84 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +/* + * If TRACE_SYSTEM is defined, that will be the directory created + * in the ftrace directory under /sys/kernel/tracing/events/ + * + * The define_trace.h below will also look for a file name of + * TRACE_SYSTEM.h where TRACE_SYSTEM is what is defined here. + * In this case, it would look for sample-trace.h + * + * If the header name will be different than the system name + * (as in this case), then you can override the header name that + * define_trace.h will look up by defining TRACE_INCLUDE_FILE + * + * This file is called sample-trace-array.h but we want the system + * to be called "sample-subsystem". Therefore we must define the name of this + * file: + * + * #define TRACE_INCLUDE_FILE sample-trace-array + * + * As we do in the bottom of this file. + * + * Notice that TRACE_SYSTEM should be defined outside of #if + * protection, just like TRACE_INCLUDE_FILE. + */ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM sample-subsystem + +/* + * TRACE_SYSTEM is expected to be a C valid variable (alpha-numeric + * and underscore), although it may start with numbers. If for some + * reason it is not, you need to add the following lines: + */ +#undef TRACE_SYSTEM_VAR +#define TRACE_SYSTEM_VAR sample_subsystem + +/* + * But the above is only needed if TRACE_SYSTEM is not alpha-numeric + * and underscored. By default, TRACE_SYSTEM_VAR will be equal to + * TRACE_SYSTEM. As TRACE_SYSTEM_VAR must be alpha-numeric, if + * TRACE_SYSTEM is not, then TRACE_SYSTEM_VAR must be defined with + * only alpha-numeric and underscores. + * + * The TRACE_SYSTEM_VAR is only used internally and not visible to + * user space. + */ + +/* + * Notice that this file is not protected like a normal header. + * We also must allow for rereading of this file. The + * + * || defined(TRACE_HEADER_MULTI_READ) + * + * serves this purpose. + */ +#if !defined(_SAMPLE_TRACE_ARRAY_H) || defined(TRACE_HEADER_MULTI_READ) +#define _SAMPLE_TRACE_ARRAY_H + +#include +TRACE_EVENT(sample_event, + + TP_PROTO(int count, unsigned long time), + + TP_ARGS(count, time), + + TP_STRUCT__entry( + __field(int, count) + __field(unsigned long, time) + ), + + TP_fast_assign( + __entry->count = count; + __entry->time = time; + ), + + TP_printk("count value=%d at jiffies=%lu", __entry->count, + __entry->time) + ); +#endif + +#undef TRACE_INCLUDE_PATH +#define TRACE_INCLUDE_PATH . +#define TRACE_INCLUDE_FILE sample-trace-array +#include -- cgit v1.3.1