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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Tty buffer allocation management
  */
 
 #include <linux/types.h>
 #include <linux/errno.h>
 #include <linux/minmax.h>
 #include <linux/tty.h>
 #include <linux/tty_driver.h>
 #include <linux/tty_flip.h>
 #include <linux/timer.h>
 #include <linux/string.h>
 #include <linux/slab.h>
 #include <linux/sched.h>
 #include <linux/wait.h>
 #include <linux/bitops.h>
 #include <linux/delay.h>
 #include <linux/module.h>
 #include <linux/ratelimit.h>
 #include "tty.h"
 
 #define MIN_TTYB_SIZE   256
 #define TTYB_ALIGN_MASK 255
 
 /*
  * Byte threshold to limit memory consumption for flip buffers.
  * The actual memory limit is > 2x this amount.
  */
 #define TTYB_DEFAULT_MEM_LIMIT  (640 * 1024UL)
 
 /*
  * We default to dicing tty buffer allocations to this many characters
  * in order to avoid multiple page allocations. We know the size of
  * tty_buffer itself but it must also be taken into account that the
  * buffer is 256 byte aligned. See tty_buffer_find for the allocation
  * logic this must match.
  */
 
 #define TTY_BUFFER_PAGE (((PAGE_SIZE - sizeof(struct tty_buffer)) / 2) & ~0xFF)
 
 /**
  * tty_buffer_lock_exclusive    -   gain exclusive access to buffer
  * @port: tty port owning the flip buffer
  *
  * Guarantees safe use of the &tty_ldisc_ops.receive_buf() method by excluding
  * the buffer work and any pending flush from using the flip buffer. Data can
  * continue to be added concurrently to the flip buffer from the driver side.
  *
  * See also tty_buffer_unlock_exclusive().
  */
 void tty_buffer_lock_exclusive(struct tty_port *port)
 {
     struct tty_bufhead *buf = &port->buf;
 
     atomic_inc(&buf->priority);
     mutex_lock(&buf->lock);
 }
 EXPORT_SYMBOL_GPL(tty_buffer_lock_exclusive);
 
 /**
  * tty_buffer_unlock_exclusive  -   release exclusive access
  * @port: tty port owning the flip buffer
  *
  * The buffer work is restarted if there is data in the flip buffer.
  *
  * See also tty_buffer_lock_exclusive().
  */
 void tty_buffer_unlock_exclusive(struct tty_port *port)
 {
     struct tty_bufhead *buf = &port->buf;
     int restart;
 
     restart = buf->head->commit != buf->head->read;
 
     atomic_dec(&buf->priority);
     mutex_unlock(&buf->lock);
     if (restart)
         queue_work(system_unbound_wq, &buf->work);
 }
 EXPORT_SYMBOL_GPL(tty_buffer_unlock_exclusive);
 
 /**
  * tty_buffer_space_avail   -   return unused buffer space
  * @port: tty port owning the flip buffer
  *
  * Returns: the # of bytes which can be written by the driver without reaching
  * the buffer limit.
  *
  * Note: this does not guarantee that memory is available to write the returned
  * # of bytes (use tty_prepare_flip_string() to pre-allocate if memory
  * guarantee is required).
  */
 unsigned int tty_buffer_space_avail(struct tty_port *port)
 {
     int space = port->buf.mem_limit - atomic_read(&port->buf.mem_used);
 
     return max(space, 0);
 }
 EXPORT_SYMBOL_GPL(tty_buffer_space_avail);
 
 static void tty_buffer_reset(struct tty_buffer *p, size_t size)
 {
     p->used = 0;
     p->size = size;
     p->next = NULL;
     p->commit = 0;
     p->lookahead = 0;
     p->read = 0;
     p->flags = 0;
 }
 
 /**
  * tty_buffer_free_all      -   free buffers used by a tty
  * @port: tty port to free from
  *
  * Remove all the buffers pending on a tty whether queued with data or in the
  * free ring. Must be called when the tty is no longer in use.
  */
 void tty_buffer_free_all(struct tty_port *port)
 {
     struct tty_bufhead *buf = &port->buf;
     struct tty_buffer *p, *next;
     struct llist_node *llist;
     unsigned int freed = 0;
     int still_used;
 
     while ((p = buf->head) != NULL) {
         buf->head = p->next;
         freed += p->size;
         if (p->size > 0)
             kfree(p);
     }
     llist = llist_del_all(&buf->free);
     llist_for_each_entry_safe(p, next, llist, free)
         kfree(p);
 
     tty_buffer_reset(&buf->sentinel, 0);
     buf->head = &buf->sentinel;
     buf->tail = &buf->sentinel;
 
     still_used = atomic_xchg(&buf->mem_used, 0);
     WARN(still_used != freed, "we still have not freed %d bytes!",
             still_used - freed);
 }
 
 /**
  * tty_buffer_alloc -   allocate a tty buffer
  * @port: tty port
  * @size: desired size (characters)
  *
  * Allocate a new tty buffer to hold the desired number of characters. We
  * round our buffers off in 256 character chunks to get better allocation
  * behaviour.
  *
  * Returns: %NULL if out of memory or the allocation would exceed the per
  * device queue.
  */
 static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size)
 {
     struct llist_node *free;
     struct tty_buffer *p;
 
     /* Round the buffer size out */
     size = __ALIGN_MASK(size, TTYB_ALIGN_MASK);
 
     if (size <= MIN_TTYB_SIZE) {
         free = llist_del_first(&port->buf.free);
         if (free) {
             p = llist_entry(free, struct tty_buffer, free);
             goto found;
         }
     }
 
     /* Should possibly check if this fails for the largest buffer we
      * have queued and recycle that ?
      */
     if (atomic_read(&port->buf.mem_used) > port->buf.mem_limit)
         return NULL;
     p = kmalloc(sizeof(struct tty_buffer) + 2 * size,
             GFP_ATOMIC | __GFP_NOWARN);
     if (p == NULL)
         return NULL;
 
 found:
     tty_buffer_reset(p, size);
     atomic_add(size, &port->buf.mem_used);
     return p;
 }
 
 /**
  * tty_buffer_free      -   free a tty buffer
  * @port: tty port owning the buffer
  * @b: the buffer to free
  *
  * Free a tty buffer, or add it to the free list according to our internal
  * strategy.
  */
 static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b)
 {
     struct tty_bufhead *buf = &port->buf;
 
     /* Dumb strategy for now - should keep some stats */
     WARN_ON(atomic_sub_return(b->size, &buf->mem_used) < 0);
 
     if (b->size > MIN_TTYB_SIZE)
         kfree(b);
     else if (b->size > 0)
         llist_add(&b->free, &buf->free);
 }
 
 /**
  * tty_buffer_flush     -   flush full tty buffers
  * @tty: tty to flush
  * @ld: optional ldisc ptr (must be referenced)
  *
  * Flush all the buffers containing receive data. If @ld != %NULL, flush the
  * ldisc input buffer.
  *
  * Locking: takes buffer lock to ensure single-threaded flip buffer 'consumer'.
  */
 void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld)
 {
     struct tty_port *port = tty->port;
     struct tty_bufhead *buf = &port->buf;
     struct tty_buffer *next;
 
     atomic_inc(&buf->priority);
 
     mutex_lock(&buf->lock);
     /* paired w/ release in __tty_buffer_request_room; ensures there are
      * no pending memory accesses to the freed buffer
      */
     while ((next = smp_load_acquire(&buf->head->next)) != NULL) {
         tty_buffer_free(port, buf->head);
         buf->head = next;
     }
     buf->head->read = buf->head->commit;
     buf->head->lookahead = buf->head->read;
 
     if (ld && ld->ops->flush_buffer)
         ld->ops->flush_buffer(tty);
 
     atomic_dec(&buf->priority);
     mutex_unlock(&buf->lock);
 }
 
 /**
  * __tty_buffer_request_room    -   grow tty buffer if needed
  * @port: tty port
  * @size: size desired
  * @flags: buffer flags if new buffer allocated (default = 0)
  *
  * Make at least @size bytes of linear space available for the tty buffer.
  *
  * Will change over to a new buffer if the current buffer is encoded as
  * %TTY_NORMAL (so has no flags buffer) and the new buffer requires a flags
  * buffer.
  *
  * Returns: the size we managed to find.
  */
 static int __tty_buffer_request_room(struct tty_port *port, size_t size,
                      int flags)
 {
     struct tty_bufhead *buf = &port->buf;
     struct tty_buffer *b, *n;
     int left, change;
 
     b = buf->tail;
     if (b->flags & TTYB_NORMAL)
         left = 2 * b->size - b->used;
     else
         left = b->size - b->used;
 
     change = (b->flags & TTYB_NORMAL) && (~flags & TTYB_NORMAL);
     if (change || left < size) {
         /* This is the slow path - looking for new buffers to use */
         n = tty_buffer_alloc(port, size);
         if (n != NULL) {
             n->flags = flags;
             buf->tail = n;
             /*
              * Paired w/ acquire in flush_to_ldisc() and lookahead_bufs()
              * ensures they see all buffer data.
              */
             smp_store_release(&b->commit, b->used);
             /*
              * Paired w/ acquire in flush_to_ldisc() and lookahead_bufs()
              * ensures the latest commit value can be read before the head
              * is advanced to the next buffer.
              */
             smp_store_release(&b->next, n);
         } else if (change)
             size = 0;
         else
             size = left;
     }
     return size;
 }
 
 int tty_buffer_request_room(struct tty_port *port, size_t size)
 {
     return __tty_buffer_request_room(port, size, 0);
 }
 EXPORT_SYMBOL_GPL(tty_buffer_request_room);
 
 /**
  * tty_insert_flip_string_fixed_flag - add characters to the tty buffer
  * @port: tty port
  * @chars: characters
  * @flag: flag value for each character
  * @size: size
  *
  * Queue a series of bytes to the tty buffering. All the characters passed are
  * marked with the supplied flag.
  *
  * Returns: the number added.
  */
 int tty_insert_flip_string_fixed_flag(struct tty_port *port,
         const unsigned char *chars, char flag, size_t size)
 {
     int copied = 0;
 
     do {
         int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
         int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0;
         int space = __tty_buffer_request_room(port, goal, flags);
         struct tty_buffer *tb = port->buf.tail;
 
         if (unlikely(space == 0))
             break;
         memcpy(char_buf_ptr(tb, tb->used), chars, space);
         if (~tb->flags & TTYB_NORMAL)
             memset(flag_buf_ptr(tb, tb->used), flag, space);
         tb->used += space;
         copied += space;
         chars += space;
         /* There is a small chance that we need to split the data over
          * several buffers. If this is the case we must loop.
          */
     } while (unlikely(size > copied));
     return copied;
 }
 EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
 
 /**
  * tty_insert_flip_string_flags -   add characters to the tty buffer
  * @port: tty port
  * @chars: characters
  * @flags: flag bytes
  * @size: size
  *
  * Queue a series of bytes to the tty buffering. For each character the flags
  * array indicates the status of the character.
  *
  * Returns: the number added.
  */
 int tty_insert_flip_string_flags(struct tty_port *port,
         const unsigned char *chars, const char *flags, size_t size)
 {
     int copied = 0;
 
     do {
         int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
         int space = tty_buffer_request_room(port, goal);
         struct tty_buffer *tb = port->buf.tail;
 
         if (unlikely(space == 0))
             break;
         memcpy(char_buf_ptr(tb, tb->used), chars, space);
         memcpy(flag_buf_ptr(tb, tb->used), flags, space);
         tb->used += space;
         copied += space;
         chars += space;
         flags += space;
         /* There is a small chance that we need to split the data over
          * several buffers. If this is the case we must loop.
          */
     } while (unlikely(size > copied));
     return copied;
 }
 EXPORT_SYMBOL(tty_insert_flip_string_flags);
 
 /**
  * __tty_insert_flip_char   -   add one character to the tty buffer
  * @port: tty port
  * @ch: character
  * @flag: flag byte
  *
  * Queue a single byte @ch to the tty buffering, with an optional flag. This is
  * the slow path of tty_insert_flip_char().
  */
 int __tty_insert_flip_char(struct tty_port *port, unsigned char ch, char flag)
 {
     struct tty_buffer *tb;
     int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0;
 
     if (!__tty_buffer_request_room(port, 1, flags))
         return 0;
 
     tb = port->buf.tail;
     if (~tb->flags & TTYB_NORMAL)
         *flag_buf_ptr(tb, tb->used) = flag;
     *char_buf_ptr(tb, tb->used++) = ch;
 
     return 1;
 }
 EXPORT_SYMBOL(__tty_insert_flip_char);
 
 /**
  * tty_prepare_flip_string  -   make room for characters
  * @port: tty port
  * @chars: return pointer for character write area
  * @size: desired size
  *
  * Prepare a block of space in the buffer for data.
  *
  * This is used for drivers that need their own block copy routines into the
  * buffer. There is no guarantee the buffer is a DMA target!
  *
  * Returns: the length available and buffer pointer (@chars) to the space which
  * is now allocated and accounted for as ready for normal characters.
  */
 int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars,
         size_t size)
 {
     int space = __tty_buffer_request_room(port, size, TTYB_NORMAL);
 
     if (likely(space)) {
         struct tty_buffer *tb = port->buf.tail;
 
         *chars = char_buf_ptr(tb, tb->used);
         if (~tb->flags & TTYB_NORMAL)
             memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space);
         tb->used += space;
     }
     return space;
 }
 EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
 
 /**
  * tty_ldisc_receive_buf    -   forward data to line discipline
  * @ld: line discipline to process input
  * @p: char buffer
  * @f: %TTY_NORMAL, %TTY_BREAK, etc. flags buffer
  * @count: number of bytes to process
  *
  * Callers other than flush_to_ldisc() need to exclude the kworker from
  * concurrent use of the line discipline, see paste_selection().
  *
  * Returns: the number of bytes processed.
  */
 int tty_ldisc_receive_buf(struct tty_ldisc *ld, const unsigned char *p,
               const char *f, int count)
 {
     if (ld->ops->receive_buf2)
         count = ld->ops->receive_buf2(ld->tty, p, f, count);
     else {
         count = min_t(int, count, ld->tty->receive_room);
         if (count && ld->ops->receive_buf)
             ld->ops->receive_buf(ld->tty, p, f, count);
     }
     return count;
 }
 EXPORT_SYMBOL_GPL(tty_ldisc_receive_buf);
 
 static void lookahead_bufs(struct tty_port *port, struct tty_buffer *head)
 {
     head->lookahead = max(head->lookahead, head->read);
 
     while (head) {
         struct tty_buffer *next;
         unsigned int count;
 
         /*
          * Paired w/ release in __tty_buffer_request_room();
          * ensures commit value read is not stale if the head
          * is advancing to the next buffer.
          */
         next = smp_load_acquire(&head->next);
         /*
          * Paired w/ release in __tty_buffer_request_room() or in
          * tty_buffer_flush(); ensures we see the committed buffer data.
          */
         count = smp_load_acquire(&head->commit) - head->lookahead;
         if (!count) {
             head = next;
             continue;
         }
 
         if (port->client_ops->lookahead_buf) {
             unsigned char *p, *f = NULL;
 
             p = char_buf_ptr(head, head->lookahead);
             if (~head->flags & TTYB_NORMAL)
                 f = flag_buf_ptr(head, head->lookahead);
 
             port->client_ops->lookahead_buf(port, p, f, count);
         }
 
         head->lookahead += count;
     }
 }
 
 static int
 receive_buf(struct tty_port *port, struct tty_buffer *head, int count)
 {
     unsigned char *p = char_buf_ptr(head, head->read);
     const char *f = NULL;
     int n;
 
     if (~head->flags & TTYB_NORMAL)
         f = flag_buf_ptr(head, head->read);
 
     n = port->client_ops->receive_buf(port, p, f, count);
     if (n > 0)
         memset(p, 0, n);
     return n;
 }
 
 /**
  * flush_to_ldisc       -   flush data from buffer to ldisc
  * @work: tty structure passed from work queue.
  *
  * This routine is called out of the software interrupt to flush data from the
  * buffer chain to the line discipline.
  *
  * The receive_buf() method is single threaded for each tty instance.
  *
  * Locking: takes buffer lock to ensure single-threaded flip buffer 'consumer'.
  */
 static void flush_to_ldisc(struct work_struct *work)
 {
     struct tty_port *port = container_of(work, struct tty_port, buf.work);
     struct tty_bufhead *buf = &port->buf;
 
     mutex_lock(&buf->lock);
 
     while (1) {
         struct tty_buffer *head = buf->head;
         struct tty_buffer *next;
         int count, rcvd;
 
         /* Ldisc or user is trying to gain exclusive access */
         if (atomic_read(&buf->priority))
             break;
 
         /* paired w/ release in __tty_buffer_request_room();
          * ensures commit value read is not stale if the head
          * is advancing to the next buffer
          */
         next = smp_load_acquire(&head->next);
         /* paired w/ release in __tty_buffer_request_room() or in
          * tty_buffer_flush(); ensures we see the committed buffer data
          */
         count = smp_load_acquire(&head->commit) - head->read;
         if (!count) {
             if (next == NULL)
                 break;
             buf->head = next;
             tty_buffer_free(port, head);
             continue;
         }
 
         rcvd = receive_buf(port, head, count);
         head->read += rcvd;
         if (rcvd < count)
             lookahead_bufs(port, head);
         if (!rcvd)
             break;
 
         if (need_resched())
             cond_resched();
     }
 
     mutex_unlock(&buf->lock);
 
 }
 
 static inline void tty_flip_buffer_commit(struct tty_buffer *tail)
 {
     /*
      * Paired w/ acquire in flush_to_ldisc(); ensures flush_to_ldisc() sees
      * buffer data.
      */
     smp_store_release(&tail->commit, tail->used);
 }
 
 /**
  * tty_flip_buffer_push     -   push terminal buffers
  * @port: tty port to push
  *
  * Queue a push of the terminal flip buffers to the line discipline. Can be
  * called from IRQ/atomic context.
  *
  * In the event of the queue being busy for flipping the work will be held off
  * and retried later.
  */
 void tty_flip_buffer_push(struct tty_port *port)
 {
     struct tty_bufhead *buf = &port->buf;
 
     tty_flip_buffer_commit(buf->tail);
     queue_work(system_unbound_wq, &buf->work);
 }
 EXPORT_SYMBOL(tty_flip_buffer_push);
 
 /**
  * tty_insert_flip_string_and_push_buffer - add characters to the tty buffer and
  *  push
  * @port: tty port
  * @chars: characters
  * @size: size
  *
  * The function combines tty_insert_flip_string() and tty_flip_buffer_push()
  * with the exception of properly holding the @port->lock.
  *
  * To be used only internally (by pty currently).
  *
  * Returns: the number added.
  */
 int tty_insert_flip_string_and_push_buffer(struct tty_port *port,
         const unsigned char *chars, size_t size)
 {
     struct tty_bufhead *buf = &port->buf;
     unsigned long flags;
 
     spin_lock_irqsave(&port->lock, flags);
     size = tty_insert_flip_string(port, chars, size);
     if (size)
         tty_flip_buffer_commit(buf->tail);
     spin_unlock_irqrestore(&port->lock, flags);
 
     queue_work(system_unbound_wq, &buf->work);
 
     return size;
 }
 
 /**
  * tty_buffer_init      -   prepare a tty buffer structure
  * @port: tty port to initialise
  *
  * Set up the initial state of the buffer management for a tty device. Must be
  * called before the other tty buffer functions are used.
  */
 void tty_buffer_init(struct tty_port *port)
 {
     struct tty_bufhead *buf = &port->buf;
 
     mutex_init(&buf->lock);
     tty_buffer_reset(&buf->sentinel, 0);
     buf->head = &buf->sentinel;
     buf->tail = &buf->sentinel;
     init_llist_head(&buf->free);
     atomic_set(&buf->mem_used, 0);
     atomic_set(&buf->priority, 0);
     INIT_WORK(&buf->work, flush_to_ldisc);
     buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT;
 }
 
 /**
  * tty_buffer_set_limit     -   change the tty buffer memory limit
  * @port: tty port to change
  * @limit: memory limit to set
  *
  * Change the tty buffer memory limit.
  *
  * Must be called before the other tty buffer functions are used.
  */
 int tty_buffer_set_limit(struct tty_port *port, int limit)
 {
     if (limit < MIN_TTYB_SIZE)
         return -EINVAL;
     port->buf.mem_limit = limit;
     return 0;
 }
 EXPORT_SYMBOL_GPL(tty_buffer_set_limit);
 
 /* slave ptys can claim nested buffer lock when handling BRK and INTR */
 void tty_buffer_set_lock_subclass(struct tty_port *port)
 {
     lockdep_set_subclass(&port->buf.lock, TTY_LOCK_SLAVE);
 }
 
 bool tty_buffer_restart_work(struct tty_port *port)
 {
     return queue_work(system_unbound_wq, &port->buf.work);
 }
 
 bool tty_buffer_cancel_work(struct tty_port *port)
 {
     return cancel_work_sync(&port->buf.work);
 }
 
 void tty_buffer_flush_work(struct tty_port *port)
 {
     flush_work(&port->buf.work);
 }

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