Use 16-bit head and tail to track the pipe buffer production and
consumption.
Since "pipe->max_usage" and "pipe->ring_size" must fall between the head
and the tail limits, convert them to unsigned short as well to catch any
cases of unsigned arithmetic going wrong.
Part of fs/fuse/dev.c, fs/splice.c, mm/filemap.c, and mm/shmem.c were
touched to accommodate the "unsigned short" based calculations of
pipe_occupancy().
pipe->tail is incremented always with both "pipe->mutex" and
"pipe->rd_wait.lock" held for pipes with watch queue. pipe_write() exits
early if pipe has a watch queue but otherwise takes the "pipe->muxtex"
before updating pipe->head. post_one_notification() holds the
"pipe->rd_wait.lock" when updating pipe->head.
Updates to "pipe->head" and "pipe->tail" are always mutually exclusive,
either guarded by "pipe->mutex" or by "pipe->rd_wait.lock". Even a RMW
updates to the 16-bits fields should be safe because of those
synchronization primitives on architectures that cannot do an atomic
16-bit store.
Signed-off-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
---
fs/fuse/dev.c | 7 +++---
fs/pipe.c | 31 +++++++++++++-------------
fs/splice.c | 47 ++++++++++++++++++++-------------------
include/linux/pipe_fs_i.h | 39 +++++++++++---------------------
kernel/watch_queue.c | 3 ++-
mm/filemap.c | 5 +++--
mm/shmem.c | 5 +++--
7 files changed, 65 insertions(+), 72 deletions(-)
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 2b2d1b755544..993e6dc24de1 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1440,6 +1440,7 @@ static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
int page_nr = 0;
struct pipe_buffer *bufs;
struct fuse_copy_state cs;
+ unsigned short free_slots;
struct fuse_dev *fud = fuse_get_dev(in);
if (!fud)
@@ -1457,7 +1458,8 @@ static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
if (ret < 0)
goto out;
- if (pipe_occupancy(pipe->head, pipe->tail) + cs.nr_segs > pipe->max_usage) {
+ free_slots = pipe->max_usage - pipe_occupancy(pipe->head, pipe->tail);
+ if (free_slots < cs.nr_segs) {
ret = -EIO;
goto out;
}
@@ -2107,9 +2109,8 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
struct file *out, loff_t *ppos,
size_t len, unsigned int flags)
{
- unsigned int head, tail, mask, count;
+ unsigned short head, tail, mask, count, idx;
unsigned nbuf;
- unsigned idx;
struct pipe_buffer *bufs;
struct fuse_copy_state cs;
struct fuse_dev *fud;
diff --git a/fs/pipe.c b/fs/pipe.c
index 3ca3103e1de7..b8d87eabff79 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -216,9 +216,9 @@ static inline bool pipe_readable(const struct pipe_inode_info *pipe)
return !pipe_empty(idx.head, idx.tail) || !writers;
}
-static inline unsigned int pipe_update_tail(struct pipe_inode_info *pipe,
- struct pipe_buffer *buf,
- unsigned int tail)
+static inline unsigned short pipe_update_tail(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf,
+ unsigned short tail)
{
pipe_buf_release(pipe, buf);
@@ -272,9 +272,9 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
*/
for (;;) {
/* Read ->head with a barrier vs post_one_notification() */
- unsigned int head = smp_load_acquire(&pipe->head);
- unsigned int tail = pipe->tail;
- unsigned int mask = pipe->ring_size - 1;
+ unsigned short head = smp_load_acquire(&pipe->head);
+ unsigned short tail = pipe->tail;
+ unsigned short mask = pipe->ring_size - 1;
#ifdef CONFIG_WATCH_QUEUE
if (pipe->note_loss) {
@@ -417,7 +417,7 @@ static inline int is_packetized(struct file *file)
static inline bool pipe_writable(const struct pipe_inode_info *pipe)
{
union pipe_index idx = { .head_tail = READ_ONCE(pipe->head_tail) };
- unsigned int max_usage = READ_ONCE(pipe->max_usage);
+ unsigned short max_usage = READ_ONCE(pipe->max_usage);
return !pipe_full(idx.head, idx.tail, max_usage) ||
!READ_ONCE(pipe->readers);
@@ -428,7 +428,7 @@ 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;
+ unsigned short head;
ssize_t ret = 0;
size_t total_len = iov_iter_count(from);
ssize_t chars;
@@ -471,7 +471,7 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
was_empty = pipe_empty(head, pipe->tail);
chars = total_len & (PAGE_SIZE-1);
if (chars && !was_empty) {
- unsigned int mask = pipe->ring_size - 1;
+ unsigned short mask = pipe->ring_size - 1;
struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
int offset = buf->offset + buf->len;
@@ -614,7 +614,8 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
struct pipe_inode_info *pipe = filp->private_data;
- unsigned int count, head, tail, mask;
+ unsigned short head, tail, mask;
+ unsigned int count;
switch (cmd) {
case FIONREAD:
@@ -1270,10 +1271,10 @@ unsigned int round_pipe_size(unsigned int size)
int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
{
struct pipe_buffer *bufs;
- unsigned int head, tail, mask, n;
+ unsigned short head, tail, mask, n;
/* nr_slots larger than limits of pipe->{head,tail} */
- if (unlikely(nr_slots > BIT(BITS_PER_TYPE(pipe_index_t) - 1)))
+ if (unlikely(nr_slots > USHRT_MAX))
return -EINVAL;
bufs = kcalloc(nr_slots, sizeof(*bufs),
@@ -1298,13 +1299,13 @@ int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
* and adjust the indices.
*/
if (n > 0) {
- unsigned int h = head & mask;
- unsigned int t = tail & mask;
+ unsigned short h = head & mask;
+ unsigned short t = tail & mask;
if (h > t) {
memcpy(bufs, pipe->bufs + t,
n * sizeof(struct pipe_buffer));
} else {
- unsigned int tsize = pipe->ring_size - t;
+ unsigned short tsize = pipe->ring_size - t;
if (h > 0)
memcpy(bufs + tsize, pipe->bufs,
h * sizeof(struct pipe_buffer));
diff --git a/fs/splice.c b/fs/splice.c
index e51f33aca032..891a7cf9fb55 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -198,9 +198,9 @@ ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
struct splice_pipe_desc *spd)
{
unsigned int spd_pages = spd->nr_pages;
- unsigned int tail = pipe->tail;
- unsigned int head = pipe->head;
- unsigned int mask = pipe->ring_size - 1;
+ unsigned short tail = pipe->tail;
+ unsigned short head = pipe->head;
+ unsigned short mask = pipe->ring_size - 1;
ssize_t ret = 0;
int page_nr = 0;
@@ -245,9 +245,9 @@ EXPORT_SYMBOL_GPL(splice_to_pipe);
ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
{
- unsigned int head = pipe->head;
- unsigned int tail = pipe->tail;
- unsigned int mask = pipe->ring_size - 1;
+ unsigned short head = pipe->head;
+ unsigned short tail = pipe->tail;
+ unsigned short mask = pipe->ring_size - 1;
int ret;
if (unlikely(!pipe->readers)) {
@@ -271,7 +271,7 @@ EXPORT_SYMBOL(add_to_pipe);
*/
int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
{
- unsigned int max_usage = READ_ONCE(pipe->max_usage);
+ unsigned short max_usage = READ_ONCE(pipe->max_usage);
spd->nr_pages_max = max_usage;
if (max_usage <= PIPE_DEF_BUFFERS)
@@ -327,12 +327,13 @@ ssize_t copy_splice_read(struct file *in, loff_t *ppos,
struct kiocb kiocb;
struct page **pages;
ssize_t ret;
- size_t used, npages, chunk, remain, keep = 0;
+ size_t npages, chunk, remain, keep = 0;
+ unsigned short used;
int i;
/* Work out how much data we can actually add into the pipe */
used = pipe_occupancy(pipe->head, pipe->tail);
- npages = max_t(ssize_t, pipe->max_usage - used, 0);
+ npages = max_t(unsigned short, pipe->max_usage - used, 0);
len = min_t(size_t, len, npages * PAGE_SIZE);
npages = DIV_ROUND_UP(len, PAGE_SIZE);
@@ -445,9 +446,9 @@ static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
splice_actor *actor)
{
- unsigned int head = pipe->head;
- unsigned int tail = pipe->tail;
- unsigned int mask = pipe->ring_size - 1;
+ unsigned short head = pipe->head;
+ unsigned short tail = pipe->tail;
+ unsigned short mask = pipe->ring_size - 1;
int ret;
while (!pipe_empty(head, tail)) {
@@ -494,8 +495,8 @@ static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_des
/* We know we have a pipe buffer, but maybe it's empty? */
static inline bool eat_empty_buffer(struct pipe_inode_info *pipe)
{
- unsigned int tail = pipe->tail;
- unsigned int mask = pipe->ring_size - 1;
+ unsigned short tail = pipe->tail;
+ unsigned short mask = pipe->ring_size - 1;
struct pipe_buffer *buf = &pipe->bufs[tail & mask];
if (unlikely(!buf->len)) {
@@ -690,7 +691,7 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
while (sd.total_len) {
struct kiocb kiocb;
struct iov_iter from;
- unsigned int head, tail, mask;
+ unsigned short head, tail, mask;
size_t left;
int n;
@@ -809,7 +810,7 @@ ssize_t splice_to_socket(struct pipe_inode_info *pipe, struct file *out,
pipe_lock(pipe);
while (len > 0) {
- unsigned int head, tail, mask, bc = 0;
+ unsigned short head, tail, mask, bc = 0;
size_t remain = len;
/*
@@ -960,7 +961,7 @@ static ssize_t do_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
- unsigned int p_space;
+ unsigned short p_space;
if (unlikely(!(in->f_mode & FMODE_READ)))
return -EBADF;
@@ -1724,9 +1725,9 @@ static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
size_t len, unsigned int flags)
{
struct pipe_buffer *ibuf, *obuf;
- unsigned int i_head, o_head;
- unsigned int i_tail, o_tail;
- unsigned int i_mask, o_mask;
+ unsigned short i_head, o_head;
+ unsigned short i_tail, o_tail;
+ unsigned short i_mask, o_mask;
int ret = 0;
bool input_wakeup = false;
@@ -1861,9 +1862,9 @@ static ssize_t link_pipe(struct pipe_inode_info *ipipe,
size_t len, unsigned int flags)
{
struct pipe_buffer *ibuf, *obuf;
- unsigned int i_head, o_head;
- unsigned int i_tail, o_tail;
- unsigned int i_mask, o_mask;
+ unsigned short i_head, o_head;
+ unsigned short i_tail, o_tail;
+ unsigned short i_mask, o_mask;
ssize_t ret = 0;
/*
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index e572e6fc4f81..0997c028548c 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -31,19 +31,6 @@ struct pipe_buffer {
unsigned long private;
};
-/*
- * Really only alpha needs 32-bit fields, but
- * might as well do it for 64-bit architectures
- * since that's what we've historically done,
- * and it makes 'head_tail' always be a simple
- * 'unsigned long'.
- */
-#ifdef CONFIG_64BIT
-typedef unsigned int pipe_index_t;
-#else
-typedef unsigned short pipe_index_t;
-#endif
-
/*
* We have to declare this outside 'struct pipe_inode_info',
* but then we can't use 'union pipe_index' for an anonymous
@@ -51,10 +38,10 @@ typedef unsigned short pipe_index_t;
* below. Annoying.
*/
union pipe_index {
- unsigned long head_tail;
+ unsigned int head_tail;
struct {
- pipe_index_t head;
- pipe_index_t tail;
+ unsigned short head;
+ unsigned short tail;
};
};
@@ -89,15 +76,15 @@ struct pipe_inode_info {
/* This has to match the 'union pipe_index' above */
union {
- unsigned long head_tail;
+ unsigned int head_tail;
struct {
- pipe_index_t head;
- pipe_index_t tail;
+ unsigned short head;
+ unsigned short tail;
};
};
- unsigned int max_usage;
- unsigned int ring_size;
+ unsigned short max_usage;
+ unsigned short ring_size;
unsigned int nr_accounted;
unsigned int readers;
unsigned int writers;
@@ -181,7 +168,7 @@ static inline bool pipe_has_watch_queue(const struct pipe_inode_info *pipe)
* @head: The pipe ring head pointer
* @tail: The pipe ring tail pointer
*/
-static inline bool pipe_empty(unsigned int head, unsigned int tail)
+static inline bool pipe_empty(unsigned short head, unsigned short tail)
{
return head == tail;
}
@@ -191,9 +178,9 @@ static inline bool pipe_empty(unsigned int head, unsigned int tail)
* @head: The pipe ring head pointer
* @tail: The pipe ring tail pointer
*/
-static inline unsigned int pipe_occupancy(unsigned int head, unsigned int tail)
+static inline unsigned short pipe_occupancy(unsigned short head, unsigned short tail)
{
- return (pipe_index_t)(head - tail);
+ return head - tail;
}
/**
@@ -202,8 +189,8 @@ static inline unsigned int pipe_occupancy(unsigned int head, unsigned int tail)
* @tail: The pipe ring tail pointer
* @limit: The maximum amount of slots available.
*/
-static inline bool pipe_full(unsigned int head, unsigned int tail,
- unsigned int limit)
+static inline bool pipe_full(unsigned short head, unsigned short tail,
+ unsigned short limit)
{
return pipe_occupancy(head, tail) >= limit;
}
diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
index 5267adeaa403..c76cfebf46c8 100644
--- a/kernel/watch_queue.c
+++ b/kernel/watch_queue.c
@@ -101,7 +101,8 @@ static bool post_one_notification(struct watch_queue *wqueue,
struct pipe_inode_info *pipe = wqueue->pipe;
struct pipe_buffer *buf;
struct page *page;
- unsigned int head, tail, mask, note, offset, len;
+ unsigned short head, tail, mask;
+ unsigned int note, offset, len;
bool done = false;
spin_lock_irq(&pipe->rd_wait.lock);
diff --git a/mm/filemap.c b/mm/filemap.c
index d4564a79eb35..6007b2403471 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2943,9 +2943,10 @@ ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
{
struct folio_batch fbatch;
struct kiocb iocb;
- size_t total_spliced = 0, used, npages;
+ size_t total_spliced = 0, npages;
loff_t isize, end_offset;
bool writably_mapped;
+ unsigned short used;
int i, error = 0;
if (unlikely(*ppos >= in->f_mapping->host->i_sb->s_maxbytes))
@@ -2956,7 +2957,7 @@ ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
/* Work out how much data we can actually add into the pipe */
used = pipe_occupancy(pipe->head, pipe->tail);
- npages = max_t(ssize_t, pipe->max_usage - used, 0);
+ npages = max_t(unsigned short, pipe->max_usage - used, 0);
len = min_t(size_t, len, npages * PAGE_SIZE);
folio_batch_init(&fbatch);
diff --git a/mm/shmem.c b/mm/shmem.c
index 4ea6109a8043..339084e5a8a1 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -3509,13 +3509,14 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
struct inode *inode = file_inode(in);
struct address_space *mapping = inode->i_mapping;
struct folio *folio = NULL;
- size_t total_spliced = 0, used, npages, n, part;
+ size_t total_spliced = 0, npages, n, part;
+ unsigned short used;
loff_t isize;
int error = 0;
/* Work out how much data we can actually add into the pipe */
used = pipe_occupancy(pipe->head, pipe->tail);
- npages = max_t(ssize_t, pipe->max_usage - used, 0);
+ npages = max_t(unsigned short, pipe->max_usage - used, 0);
len = min_t(size_t, len, npages * PAGE_SIZE);
do {
--
2.43.0
