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n_tty: Use DIV_ROUND_UP() in room calculation
When PARMRK is set, a character can result in up to 3 chars in the read buffer. Receive code calculates for how many characters there (at least) is room. Convert an opencoded rounding in the calculation to use DIV_ROUND_UP(). Note: the room variable is decremented afterwards by one which ensures the characters will fit into the buffer for real so the code is okay despite rounding upwards. Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Link: https://lore.kernel.org/r/20230309082035.14880-6-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -36,6 +36,7 @@
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#include <linux/file.h>
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#include <linux/file.h>
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#include <linux/interrupt.h>
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#include <linux/interrupt.h>
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#include <linux/major.h>
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#include <linux/major.h>
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#include <linux/math.h>
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#include <linux/mm.h>
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/module.h>
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#include <linux/poll.h>
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#include <linux/poll.h>
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@ -1692,7 +1693,7 @@ n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
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room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
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room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
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if (I_PARMRK(tty))
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if (I_PARMRK(tty))
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room = (room + 2) / 3;
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room = DIV_ROUND_UP(room, 3);
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room--;
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room--;
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if (room <= 0) {
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if (room <= 0) {
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overflow = ldata->icanon && ldata->canon_head == tail;
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overflow = ldata->icanon && ldata->canon_head == tail;
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