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-rw-r--r--fs/pipe.c170
1 files changed, 97 insertions, 73 deletions
diff --git a/fs/pipe.c b/fs/pipe.c
index 8a2ab2f974bd..e9b361cb093e 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -43,10 +43,12 @@ unsigned long pipe_user_pages_hard;
unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
/*
- * We use a start+len construction, which provides full use of the
- * allocated memory.
- * -- Florian Coosmann (FGC)
- *
+ * We use head and tail indices that aren't masked off, except at the point of
+ * dereference, but rather they're allowed to wrap naturally. This means there
+ * isn't a dead spot in the buffer, but the ring has to be a power of two and
+ * <= 2^31.
+ * -- David Howells 2019-09-23.
+ *
* Reads with count = 0 should always return 0.
* -- Julian Bradfield 1999-06-07.
*
@@ -285,10 +287,12 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
ret = 0;
__pipe_lock(pipe);
for (;;) {
- int bufs = pipe->nrbufs;
- if (bufs) {
- int curbuf = pipe->curbuf;
- struct pipe_buffer *buf = pipe->bufs + curbuf;
+ unsigned int head = pipe->head;
+ unsigned int tail = pipe->tail;
+ unsigned int mask = pipe->ring_size - 1;
+
+ if (!pipe_empty(head, tail)) {
+ struct pipe_buffer *buf = &pipe->bufs[tail & mask];
size_t chars = buf->len;
size_t written;
int error;
@@ -321,17 +325,17 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
if (!buf->len) {
pipe_buf_release(pipe, buf);
- curbuf = (curbuf + 1) & (pipe->buffers - 1);
- pipe->curbuf = curbuf;
- pipe->nrbufs = --bufs;
+ tail++;
+ pipe->tail = tail;
do_wakeup = 1;
}
total_len -= chars;
if (!total_len)
break; /* common path: read succeeded */
+ if (!pipe_empty(head, tail)) /* More to do? */
+ continue;
}
- if (bufs) /* More to do? */
- continue;
+
if (!pipe->writers)
break;
if (!pipe->waiting_writers) {
@@ -380,6 +384,7 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
{
struct file *filp = iocb->ki_filp;
struct pipe_inode_info *pipe = filp->private_data;
+ unsigned int head, tail, max_usage, mask;
ssize_t ret = 0;
int do_wakeup = 0;
size_t total_len = iov_iter_count(from);
@@ -397,12 +402,15 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
goto out;
}
+ tail = pipe->tail;
+ head = pipe->head;
+ max_usage = pipe->ring_size;
+ mask = pipe->ring_size - 1;
+
/* We try to merge small writes */
chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
- if (pipe->nrbufs && chars != 0) {
- int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
- (pipe->buffers - 1);
- struct pipe_buffer *buf = pipe->bufs + lastbuf;
+ if (!pipe_empty(head, tail) && chars != 0) {
+ struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
int offset = buf->offset + buf->len;
if (pipe_buf_can_merge(buf) && offset + chars <= PAGE_SIZE) {
@@ -423,18 +431,16 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
}
for (;;) {
- int bufs;
-
if (!pipe->readers) {
send_sig(SIGPIPE, current, 0);
if (!ret)
ret = -EPIPE;
break;
}
- bufs = pipe->nrbufs;
- if (bufs < pipe->buffers) {
- int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
- struct pipe_buffer *buf = pipe->bufs + newbuf;
+
+ tail = pipe->tail;
+ if (!pipe_full(head, tail, max_usage)) {
+ struct pipe_buffer *buf = &pipe->bufs[head & mask];
struct page *page = pipe->tmp_page;
int copied;
@@ -470,14 +476,19 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
buf->ops = &packet_pipe_buf_ops;
buf->flags = PIPE_BUF_FLAG_PACKET;
}
- pipe->nrbufs = ++bufs;
+
+ head++;
+ pipe->head = head;
pipe->tmp_page = NULL;
if (!iov_iter_count(from))
break;
}
- if (bufs < pipe->buffers)
+
+ if (!pipe_full(head, tail, max_usage))
continue;
+
+ /* Wait for buffer space to become available. */
if (filp->f_flags & O_NONBLOCK) {
if (!ret)
ret = -EAGAIN;
@@ -515,17 +526,19 @@ out:
static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
struct pipe_inode_info *pipe = filp->private_data;
- int count, buf, nrbufs;
+ int count, head, tail, mask;
switch (cmd) {
case FIONREAD:
__pipe_lock(pipe);
count = 0;
- buf = pipe->curbuf;
- nrbufs = pipe->nrbufs;
- while (--nrbufs >= 0) {
- count += pipe->bufs[buf].len;
- buf = (buf+1) & (pipe->buffers - 1);
+ head = pipe->head;
+ tail = pipe->tail;
+ mask = pipe->ring_size - 1;
+
+ while (tail != head) {
+ count += pipe->bufs[tail & mask].len;
+ tail++;
}
__pipe_unlock(pipe);
@@ -541,21 +554,25 @@ pipe_poll(struct file *filp, poll_table *wait)
{
__poll_t mask;
struct pipe_inode_info *pipe = filp->private_data;
- int nrbufs;
+ unsigned int head = READ_ONCE(pipe->head);
+ unsigned int tail = READ_ONCE(pipe->tail);
poll_wait(filp, &pipe->wait, wait);
+ BUG_ON(pipe_occupancy(head, tail) > pipe->ring_size);
+
/* Reading only -- no need for acquiring the semaphore. */
- nrbufs = pipe->nrbufs;
mask = 0;
if (filp->f_mode & FMODE_READ) {
- mask = (nrbufs > 0) ? EPOLLIN | EPOLLRDNORM : 0;
+ if (!pipe_empty(head, tail))
+ mask |= EPOLLIN | EPOLLRDNORM;
if (!pipe->writers && filp->f_version != pipe->w_counter)
mask |= EPOLLHUP;
}
if (filp->f_mode & FMODE_WRITE) {
- mask |= (nrbufs < pipe->buffers) ? EPOLLOUT | EPOLLWRNORM : 0;
+ if (!pipe_full(head, tail, pipe->ring_size))
+ mask |= EPOLLOUT | EPOLLWRNORM;
/*
* Most Unices do not set EPOLLERR for FIFOs but on Linux they
* behave exactly like pipes for poll().
@@ -679,7 +696,7 @@ struct pipe_inode_info *alloc_pipe_info(void)
if (pipe->bufs) {
init_waitqueue_head(&pipe->wait);
pipe->r_counter = pipe->w_counter = 1;
- pipe->buffers = pipe_bufs;
+ pipe->ring_size = pipe_bufs;
pipe->user = user;
mutex_init(&pipe->mutex);
return pipe;
@@ -697,9 +714,9 @@ void free_pipe_info(struct pipe_inode_info *pipe)
{
int i;
- (void) account_pipe_buffers(pipe->user, pipe->buffers, 0);
+ (void) account_pipe_buffers(pipe->user, pipe->ring_size, 0);
free_uid(pipe->user);
- for (i = 0; i < pipe->buffers; i++) {
+ for (i = 0; i < pipe->ring_size; i++) {
struct pipe_buffer *buf = pipe->bufs + i;
if (buf->ops)
pipe_buf_release(pipe, buf);
@@ -880,7 +897,7 @@ SYSCALL_DEFINE1(pipe, int __user *, fildes)
static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
{
- int cur = *cnt;
+ int cur = *cnt;
while (cur == *cnt) {
pipe_wait(pipe);
@@ -955,7 +972,7 @@ static int fifo_open(struct inode *inode, struct file *filp)
}
}
break;
-
+
case FMODE_WRITE:
/*
* O_WRONLY
@@ -975,7 +992,7 @@ static int fifo_open(struct inode *inode, struct file *filp)
goto err_wr;
}
break;
-
+
case FMODE_READ | FMODE_WRITE:
/*
* O_RDWR
@@ -1054,14 +1071,14 @@ unsigned int round_pipe_size(unsigned long size)
static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
{
struct pipe_buffer *bufs;
- unsigned int size, nr_pages;
+ unsigned int size, nr_slots, head, tail, mask, n;
unsigned long user_bufs;
long ret = 0;
size = round_pipe_size(arg);
- nr_pages = size >> PAGE_SHIFT;
+ nr_slots = size >> PAGE_SHIFT;
- if (!nr_pages)
+ if (!nr_slots)
return -EINVAL;
/*
@@ -1071,13 +1088,13 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
* Decreasing the pipe capacity is always permitted, even
* if the user is currently over a limit.
*/
- if (nr_pages > pipe->buffers &&
+ if (nr_slots > pipe->ring_size &&
size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
return -EPERM;
- user_bufs = account_pipe_buffers(pipe->user, pipe->buffers, nr_pages);
+ user_bufs = account_pipe_buffers(pipe->user, pipe->ring_size, nr_slots);
- if (nr_pages > pipe->buffers &&
+ if (nr_slots > pipe->ring_size &&
(too_many_pipe_buffers_hard(user_bufs) ||
too_many_pipe_buffers_soft(user_bufs)) &&
is_unprivileged_user()) {
@@ -1086,17 +1103,21 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
}
/*
- * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
- * expect a lot of shrink+grow operations, just free and allocate
- * again like we would do for growing. If the pipe currently
+ * We can shrink the pipe, if arg is greater than the ring occupancy.
+ * Since we don't expect a lot of shrink+grow operations, just free and
+ * allocate again like we would do for growing. If the pipe currently
* contains more buffers than arg, then return busy.
*/
- if (nr_pages < pipe->nrbufs) {
+ mask = pipe->ring_size - 1;
+ head = pipe->head;
+ tail = pipe->tail;
+ n = pipe_occupancy(pipe->head, pipe->tail);
+ if (nr_slots < n) {
ret = -EBUSY;
goto out_revert_acct;
}
- bufs = kcalloc(nr_pages, sizeof(*bufs),
+ bufs = kcalloc(nr_slots, sizeof(*bufs),
GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
if (unlikely(!bufs)) {
ret = -ENOMEM;
@@ -1105,33 +1126,36 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
/*
* The pipe array wraps around, so just start the new one at zero
- * and adjust the indexes.
+ * and adjust the indices.
*/
- if (pipe->nrbufs) {
- unsigned int tail;
- unsigned int head;
-
- tail = pipe->curbuf + pipe->nrbufs;
- if (tail < pipe->buffers)
- tail = 0;
- else
- tail &= (pipe->buffers - 1);
-
- head = pipe->nrbufs - tail;
- if (head)
- memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
- if (tail)
- memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
+ if (n > 0) {
+ unsigned int h = head & mask;
+ unsigned int t = tail & mask;
+ if (h > t) {
+ memcpy(bufs, pipe->bufs + t,
+ n * sizeof(struct pipe_buffer));
+ } else {
+ unsigned int tsize = pipe->ring_size - t;
+ if (h > 0)
+ memcpy(bufs + tsize, pipe->bufs,
+ h * sizeof(struct pipe_buffer));
+ memcpy(bufs, pipe->bufs + t,
+ tsize * sizeof(struct pipe_buffer));
+ }
}
- pipe->curbuf = 0;
+ head = n;
+ tail = 0;
+
kfree(pipe->bufs);
pipe->bufs = bufs;
- pipe->buffers = nr_pages;
- return nr_pages * PAGE_SIZE;
+ pipe->ring_size = nr_slots;
+ pipe->tail = tail;
+ pipe->head = head;
+ return pipe->ring_size * PAGE_SIZE;
out_revert_acct:
- (void) account_pipe_buffers(pipe->user, nr_pages, pipe->buffers);
+ (void) account_pipe_buffers(pipe->user, nr_slots, pipe->ring_size);
return ret;
}
@@ -1161,7 +1185,7 @@ long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
ret = pipe_set_size(pipe, arg);
break;
case F_GETPIPE_SZ:
- ret = pipe->buffers * PAGE_SIZE;
+ ret = pipe->ring_size * PAGE_SIZE;
break;
default:
ret = -EINVAL;