pipe: add support for shrinking and growing pipes
This patch adds F_GETPIPE_SZ and F_SETPIPE_SZ fcntl() actions for
growing and shrinking the size of a pipe and adjusts pipe.c and splice.c
(and relay and network splice) usage to work with these larger (or smaller)
pipes.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 452d02f..bcba9603 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -14,6 +14,7 @@
#include <linux/dnotify.h>
#include <linux/slab.h>
#include <linux/module.h>
+#include <linux/pipe_fs_i.h>
#include <linux/security.h>
#include <linux/ptrace.h>
#include <linux/signal.h>
@@ -412,6 +413,10 @@
case F_NOTIFY:
err = fcntl_dirnotify(fd, filp, arg);
break;
+ case F_SETPIPE_SZ:
+ case F_GETPIPE_SZ:
+ err = pipe_fcntl(filp, cmd, arg);
+ break;
default:
break;
}
diff --git a/fs/pipe.c b/fs/pipe.c
index 37ba29f..054b8a6 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -11,6 +11,7 @@
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
+#include <linux/log2.h>
#include <linux/mount.h>
#include <linux/pipe_fs_i.h>
#include <linux/uio.h>
@@ -390,7 +391,7 @@
if (!buf->len) {
buf->ops = NULL;
ops->release(pipe, buf);
- curbuf = (curbuf + 1) & (PIPE_BUFFERS-1);
+ curbuf = (curbuf + 1) & (pipe->buffers - 1);
pipe->curbuf = curbuf;
pipe->nrbufs = --bufs;
do_wakeup = 1;
@@ -472,7 +473,7 @@
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);
+ (pipe->buffers - 1);
struct pipe_buffer *buf = pipe->bufs + lastbuf;
const struct pipe_buf_operations *ops = buf->ops;
int offset = buf->offset + buf->len;
@@ -518,8 +519,8 @@
break;
}
bufs = pipe->nrbufs;
- if (bufs < PIPE_BUFFERS) {
- int newbuf = (pipe->curbuf + bufs) & (PIPE_BUFFERS-1);
+ if (bufs < pipe->buffers) {
+ int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
struct pipe_buffer *buf = pipe->bufs + newbuf;
struct page *page = pipe->tmp_page;
char *src;
@@ -580,7 +581,7 @@
if (!total_len)
break;
}
- if (bufs < PIPE_BUFFERS)
+ if (bufs < pipe->buffers)
continue;
if (filp->f_flags & O_NONBLOCK) {
if (!ret)
@@ -640,7 +641,7 @@
nrbufs = pipe->nrbufs;
while (--nrbufs >= 0) {
count += pipe->bufs[buf].len;
- buf = (buf+1) & (PIPE_BUFFERS-1);
+ buf = (buf+1) & (pipe->buffers - 1);
}
mutex_unlock(&inode->i_mutex);
@@ -671,7 +672,7 @@
}
if (filp->f_mode & FMODE_WRITE) {
- mask |= (nrbufs < PIPE_BUFFERS) ? POLLOUT | POLLWRNORM : 0;
+ mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
/*
* Most Unices do not set POLLERR for FIFOs but on Linux they
* behave exactly like pipes for poll().
@@ -877,25 +878,32 @@
pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
if (pipe) {
- init_waitqueue_head(&pipe->wait);
- pipe->r_counter = pipe->w_counter = 1;
- pipe->inode = inode;
+ pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL);
+ if (pipe->bufs) {
+ init_waitqueue_head(&pipe->wait);
+ pipe->r_counter = pipe->w_counter = 1;
+ pipe->inode = inode;
+ pipe->buffers = PIPE_DEF_BUFFERS;
+ return pipe;
+ }
+ kfree(pipe);
}
- return pipe;
+ return NULL;
}
void __free_pipe_info(struct pipe_inode_info *pipe)
{
int i;
- for (i = 0; i < PIPE_BUFFERS; i++) {
+ for (i = 0; i < pipe->buffers; i++) {
struct pipe_buffer *buf = pipe->bufs + i;
if (buf->ops)
buf->ops->release(pipe, buf);
}
if (pipe->tmp_page)
__free_page(pipe->tmp_page);
+ kfree(pipe->bufs);
kfree(pipe);
}
@@ -1094,6 +1102,81 @@
}
/*
+ * Allocate a new array of pipe buffers and copy the info over. Returns the
+ * pipe size if successful, or return -ERROR on error.
+ */
+static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
+{
+ struct pipe_buffer *bufs;
+
+ /*
+ * Must be a power-of-2 currently
+ */
+ if (!is_power_of_2(arg))
+ return -EINVAL;
+
+ /*
+ * 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
+ * contains more buffers than arg, then return busy.
+ */
+ if (arg < pipe->nrbufs)
+ return -EBUSY;
+
+ bufs = kcalloc(arg, sizeof(struct pipe_buffer), GFP_KERNEL);
+ if (unlikely(!bufs))
+ return -ENOMEM;
+
+ /*
+ * The pipe array wraps around, so just start the new one at zero
+ * and adjust the indexes.
+ */
+ if (pipe->nrbufs) {
+ const unsigned int tail = pipe->nrbufs & (pipe->buffers - 1);
+ const unsigned int head = pipe->nrbufs - tail;
+
+ if (head)
+ memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
+ if (tail)
+ memcpy(bufs + head, pipe->bufs + pipe->curbuf, tail * sizeof(struct pipe_buffer));
+ }
+
+ pipe->curbuf = 0;
+ kfree(pipe->bufs);
+ pipe->bufs = bufs;
+ pipe->buffers = arg;
+ return arg;
+}
+
+long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+ struct pipe_inode_info *pipe;
+ long ret;
+
+ pipe = file->f_path.dentry->d_inode->i_pipe;
+ if (!pipe)
+ return -EBADF;
+
+ mutex_lock(&pipe->inode->i_mutex);
+
+ switch (cmd) {
+ case F_SETPIPE_SZ:
+ ret = pipe_set_size(pipe, arg);
+ break;
+ case F_GETPIPE_SZ:
+ ret = pipe->buffers;
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ }
+
+ mutex_unlock(&pipe->inode->i_mutex);
+ return ret;
+}
+
+/*
* pipefs should _never_ be mounted by userland - too much of security hassle,
* no real gain from having the whole whorehouse mounted. So we don't need
* any operations on the root directory. However, we need a non-trivial
diff --git a/fs/splice.c b/fs/splice.c
index 9313b61..ac22b00 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -193,8 +193,8 @@
break;
}
- if (pipe->nrbufs < PIPE_BUFFERS) {
- int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
+ if (pipe->nrbufs < pipe->buffers) {
+ int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
struct pipe_buffer *buf = pipe->bufs + newbuf;
buf->page = spd->pages[page_nr];
@@ -214,7 +214,7 @@
if (!--spd->nr_pages)
break;
- if (pipe->nrbufs < PIPE_BUFFERS)
+ if (pipe->nrbufs < pipe->buffers)
continue;
break;
@@ -265,6 +265,36 @@
page_cache_release(spd->pages[i]);
}
+/*
+ * Check if we need to grow the arrays holding pages and partial page
+ * descriptions.
+ */
+int splice_grow_spd(struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
+{
+ if (pipe->buffers <= PIPE_DEF_BUFFERS)
+ return 0;
+
+ spd->pages = kmalloc(pipe->buffers * sizeof(struct page *), GFP_KERNEL);
+ spd->partial = kmalloc(pipe->buffers * sizeof(struct partial_page), GFP_KERNEL);
+
+ if (spd->pages && spd->partial)
+ return 0;
+
+ kfree(spd->pages);
+ kfree(spd->partial);
+ return -ENOMEM;
+}
+
+void splice_shrink_spd(struct pipe_inode_info *pipe,
+ struct splice_pipe_desc *spd)
+{
+ if (pipe->buffers <= PIPE_DEF_BUFFERS)
+ return;
+
+ kfree(spd->pages);
+ kfree(spd->partial);
+}
+
static int
__generic_file_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
@@ -272,8 +302,8 @@
{
struct address_space *mapping = in->f_mapping;
unsigned int loff, nr_pages, req_pages;
- struct page *pages[PIPE_BUFFERS];
- struct partial_page partial[PIPE_BUFFERS];
+ struct page *pages[PIPE_DEF_BUFFERS];
+ struct partial_page partial[PIPE_DEF_BUFFERS];
struct page *page;
pgoff_t index, end_index;
loff_t isize;
@@ -286,15 +316,18 @@
.spd_release = spd_release_page,
};
+ if (splice_grow_spd(pipe, &spd))
+ return -ENOMEM;
+
index = *ppos >> PAGE_CACHE_SHIFT;
loff = *ppos & ~PAGE_CACHE_MASK;
req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
- nr_pages = min(req_pages, (unsigned)PIPE_BUFFERS);
+ nr_pages = min(req_pages, pipe->buffers);
/*
* Lookup the (hopefully) full range of pages we need.
*/
- spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
+ spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages);
index += spd.nr_pages;
/*
@@ -335,7 +368,7 @@
unlock_page(page);
}
- pages[spd.nr_pages++] = page;
+ spd.pages[spd.nr_pages++] = page;
index++;
}
@@ -356,7 +389,7 @@
* this_len is the max we'll use from this page
*/
this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
- page = pages[page_nr];
+ page = spd.pages[page_nr];
if (PageReadahead(page))
page_cache_async_readahead(mapping, &in->f_ra, in,
@@ -393,8 +426,8 @@
error = -ENOMEM;
break;
}
- page_cache_release(pages[page_nr]);
- pages[page_nr] = page;
+ page_cache_release(spd.pages[page_nr]);
+ spd.pages[page_nr] = page;
}
/*
* page was already under io and is now done, great
@@ -451,8 +484,8 @@
len = this_len;
}
- partial[page_nr].offset = loff;
- partial[page_nr].len = this_len;
+ spd.partial[page_nr].offset = loff;
+ spd.partial[page_nr].len = this_len;
len -= this_len;
loff = 0;
spd.nr_pages++;
@@ -464,12 +497,13 @@
* we got, 'nr_pages' is how many pages are in the map.
*/
while (page_nr < nr_pages)
- page_cache_release(pages[page_nr++]);
+ page_cache_release(spd.pages[page_nr++]);
in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
if (spd.nr_pages)
- return splice_to_pipe(pipe, &spd);
+ error = splice_to_pipe(pipe, &spd);
+ splice_shrink_spd(pipe, &spd);
return error;
}
@@ -560,9 +594,9 @@
unsigned int nr_pages;
unsigned int nr_freed;
size_t offset;
- struct page *pages[PIPE_BUFFERS];
- struct partial_page partial[PIPE_BUFFERS];
- struct iovec vec[PIPE_BUFFERS];
+ struct page *pages[PIPE_DEF_BUFFERS];
+ struct partial_page partial[PIPE_DEF_BUFFERS];
+ struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
pgoff_t index;
ssize_t res;
size_t this_len;
@@ -576,11 +610,22 @@
.spd_release = spd_release_page,
};
+ if (splice_grow_spd(pipe, &spd))
+ return -ENOMEM;
+
+ res = -ENOMEM;
+ vec = __vec;
+ if (pipe->buffers > PIPE_DEF_BUFFERS) {
+ vec = kmalloc(pipe->buffers * sizeof(struct iovec), GFP_KERNEL);
+ if (!vec)
+ goto shrink_ret;
+ }
+
index = *ppos >> PAGE_CACHE_SHIFT;
offset = *ppos & ~PAGE_CACHE_MASK;
nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
- for (i = 0; i < nr_pages && i < PIPE_BUFFERS && len; i++) {
+ for (i = 0; i < nr_pages && i < pipe->buffers && len; i++) {
struct page *page;
page = alloc_page(GFP_USER);
@@ -591,7 +636,7 @@
this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
vec[i].iov_base = (void __user *) page_address(page);
vec[i].iov_len = this_len;
- pages[i] = page;
+ spd.pages[i] = page;
spd.nr_pages++;
len -= this_len;
offset = 0;
@@ -610,11 +655,11 @@
nr_freed = 0;
for (i = 0; i < spd.nr_pages; i++) {
this_len = min_t(size_t, vec[i].iov_len, res);
- partial[i].offset = 0;
- partial[i].len = this_len;
+ spd.partial[i].offset = 0;
+ spd.partial[i].len = this_len;
if (!this_len) {
- __free_page(pages[i]);
- pages[i] = NULL;
+ __free_page(spd.pages[i]);
+ spd.pages[i] = NULL;
nr_freed++;
}
res -= this_len;
@@ -625,13 +670,18 @@
if (res > 0)
*ppos += res;
+shrink_ret:
+ if (vec != __vec)
+ kfree(vec);
+ splice_shrink_spd(pipe, &spd);
return res;
err:
for (i = 0; i < spd.nr_pages; i++)
- __free_page(pages[i]);
+ __free_page(spd.pages[i]);
- return error;
+ res = error;
+ goto shrink_ret;
}
EXPORT_SYMBOL(default_file_splice_read);
@@ -784,7 +834,7 @@
if (!buf->len) {
buf->ops = NULL;
ops->release(pipe, buf);
- pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
+ pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
pipe->nrbufs--;
if (pipe->inode)
sd->need_wakeup = true;
@@ -1211,7 +1261,7 @@
* If we did an incomplete transfer we must release
* the pipe buffers in question:
*/
- for (i = 0; i < PIPE_BUFFERS; i++) {
+ for (i = 0; i < pipe->buffers; i++) {
struct pipe_buffer *buf = pipe->bufs + i;
if (buf->ops) {
@@ -1371,7 +1421,8 @@
*/
static int get_iovec_page_array(const struct iovec __user *iov,
unsigned int nr_vecs, struct page **pages,
- struct partial_page *partial, int aligned)
+ struct partial_page *partial, int aligned,
+ unsigned int pipe_buffers)
{
int buffers = 0, error = 0;
@@ -1414,8 +1465,8 @@
break;
npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
- if (npages > PIPE_BUFFERS - buffers)
- npages = PIPE_BUFFERS - buffers;
+ if (npages > pipe_buffers - buffers)
+ npages = pipe_buffers - buffers;
error = get_user_pages_fast((unsigned long)base, npages,
0, &pages[buffers]);
@@ -1450,7 +1501,7 @@
* or if we mapped the max number of pages that we have
* room for.
*/
- if (error < npages || buffers == PIPE_BUFFERS)
+ if (error < npages || buffers == pipe_buffers)
break;
nr_vecs--;
@@ -1593,8 +1644,8 @@
unsigned long nr_segs, unsigned int flags)
{
struct pipe_inode_info *pipe;
- struct page *pages[PIPE_BUFFERS];
- struct partial_page partial[PIPE_BUFFERS];
+ struct page *pages[PIPE_DEF_BUFFERS];
+ struct partial_page partial[PIPE_DEF_BUFFERS];
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
@@ -1602,17 +1653,25 @@
.ops = &user_page_pipe_buf_ops,
.spd_release = spd_release_page,
};
+ long ret;
pipe = pipe_info(file->f_path.dentry->d_inode);
if (!pipe)
return -EBADF;
- spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
- flags & SPLICE_F_GIFT);
- if (spd.nr_pages <= 0)
- return spd.nr_pages;
+ if (splice_grow_spd(pipe, &spd))
+ return -ENOMEM;
- return splice_to_pipe(pipe, &spd);
+ spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
+ spd.partial, flags & SPLICE_F_GIFT,
+ pipe->buffers);
+ if (spd.nr_pages <= 0)
+ ret = spd.nr_pages;
+ else
+ ret = splice_to_pipe(pipe, &spd);
+
+ splice_shrink_spd(pipe, &spd);
+ return ret;
}
/*
@@ -1738,13 +1797,13 @@
* Check ->nrbufs without the inode lock first. This function
* is speculative anyways, so missing one is ok.
*/
- if (pipe->nrbufs < PIPE_BUFFERS)
+ if (pipe->nrbufs < pipe->buffers)
return 0;
ret = 0;
pipe_lock(pipe);
- while (pipe->nrbufs >= PIPE_BUFFERS) {
+ while (pipe->nrbufs >= pipe->buffers) {
if (!pipe->readers) {
send_sig(SIGPIPE, current, 0);
ret = -EPIPE;
@@ -1810,7 +1869,7 @@
* Cannot make any progress, because either the input
* pipe is empty or the output pipe is full.
*/
- if (!ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS) {
+ if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
/* Already processed some buffers, break */
if (ret)
break;
@@ -1831,7 +1890,7 @@
}
ibuf = ipipe->bufs + ipipe->curbuf;
- nbuf = (opipe->curbuf + opipe->nrbufs) % PIPE_BUFFERS;
+ nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
obuf = opipe->bufs + nbuf;
if (len >= ibuf->len) {
@@ -1841,7 +1900,7 @@
*obuf = *ibuf;
ibuf->ops = NULL;
opipe->nrbufs++;
- ipipe->curbuf = (ipipe->curbuf + 1) % PIPE_BUFFERS;
+ ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
ipipe->nrbufs--;
input_wakeup = true;
} else {
@@ -1914,11 +1973,11 @@
* If we have iterated all input buffers or ran out of
* output room, break.
*/
- if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
+ if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
break;
- ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
- nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
+ ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
+ nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
/*
* Get a reference to this pipe buffer,