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 --- drivers/accessibility/speakup/buffers.c | 124 ++++++++++++++++++++++++++++++++ 1 file changed, 124 insertions(+) create mode 100644 drivers/accessibility/speakup/buffers.c (limited to 'drivers/accessibility/speakup/buffers.c') diff --git a/drivers/accessibility/speakup/buffers.c b/drivers/accessibility/speakup/buffers.c new file mode 100644 index 000000000..1371ced2f --- /dev/null +++ b/drivers/accessibility/speakup/buffers.c @@ -0,0 +1,124 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include + +#include "speakup.h" +#include "spk_priv.h" + +#define SYNTH_BUF_SIZE 8192 /* currently 8K bytes */ + +static u16 synth_buffer[SYNTH_BUF_SIZE]; /* guess what this is for! */ +static u16 *buff_in = synth_buffer; +static u16 *buff_out = synth_buffer; +static u16 *buffer_end = synth_buffer + SYNTH_BUF_SIZE - 1; + +/* These try to throttle applications by stopping the TTYs + * Note: we need to make sure that we will restart them eventually, which is + * usually not possible to do from the notifiers. TODO: it should be possible + * starting from linux 2.6.26. + * + * So we only stop when we know alive == 1 (else we discard the data anyway), + * and the alive synth will eventually call start_ttys from the thread context. + */ +void speakup_start_ttys(void) +{ + int i; + + for (i = 0; i < MAX_NR_CONSOLES; i++) { + if (speakup_console[i] && speakup_console[i]->tty_stopped) + continue; + if (vc_cons[i].d && vc_cons[i].d->port.tty) + start_tty(vc_cons[i].d->port.tty); + } +} +EXPORT_SYMBOL_GPL(speakup_start_ttys); + +static void speakup_stop_ttys(void) +{ + int i; + + for (i = 0; i < MAX_NR_CONSOLES; i++) + if (vc_cons[i].d && vc_cons[i].d->port.tty) + stop_tty(vc_cons[i].d->port.tty); +} + +static int synth_buffer_free(void) +{ + int chars_free; + + if (buff_in >= buff_out) + chars_free = SYNTH_BUF_SIZE - (buff_in - buff_out); + else + chars_free = buff_out - buff_in; + return chars_free; +} + +int synth_buffer_empty(void) +{ + return (buff_in == buff_out); +} +EXPORT_SYMBOL_GPL(synth_buffer_empty); + +void synth_buffer_add(u16 ch) +{ + if (!synth->alive) { + /* This makes sure that we won't stop TTYs if there is no synth + * to restart them + */ + return; + } + if (synth_buffer_free() <= 100) { + synth_start(); + speakup_stop_ttys(); + } + if (synth_buffer_free() <= 1) + return; + *buff_in++ = ch; + if (buff_in > buffer_end) + buff_in = synth_buffer; + /* We have written something to the speech synthesis, so we are not + * paused any more. + */ + spk_paused = false; +} + +u16 synth_buffer_getc(void) +{ + u16 ch; + + if (buff_out == buff_in) + return 0; + ch = *buff_out++; + if (buff_out > buffer_end) + buff_out = synth_buffer; + return ch; +} +EXPORT_SYMBOL_GPL(synth_buffer_getc); + +u16 synth_buffer_peek(void) +{ + if (buff_out == buff_in) + return 0; + return *buff_out; +} +EXPORT_SYMBOL_GPL(synth_buffer_peek); + +void synth_buffer_skip_nonlatin1(void) +{ + while (buff_out != buff_in) { + if (*buff_out < 0x100) + return; + buff_out++; + if (buff_out > buffer_end) + buff_out = synth_buffer; + } +} +EXPORT_SYMBOL_GPL(synth_buffer_skip_nonlatin1); + +void synth_buffer_clear(void) +{ + buff_in = synth_buffer; + buff_out = synth_buffer; +} +EXPORT_SYMBOL_GPL(synth_buffer_clear); -- cgit v1.3.1