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>

1 files changed, 105 insertions, 46 deletions

diff --git a/fs/splice.c b/fs/splice.c
index 9313b6124a2e..ac22b00d86c3 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -193,8 +193,8 @@ ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
                         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 @@ ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
 
                         if (!--spd->nr_pages)
                                 break;
-                        if (pipe->nrbufs < PIPE_BUFFERS)
+                        if (pipe->nrbufs < pipe->buffers)
                                 continue;
 
                         break;
@@ -265,6 +265,36 @@ static void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
         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 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
 {
         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 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
                 .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 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
                         unlock_page(page);
                 }
 
-                pages[spd.nr_pages++] = page;
+                spd.pages[spd.nr_pages++] = page;
                 index++;
         }
 
@@ -356,7 +389,7 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
                  * 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 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
                                         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 @@ fill_it:
                         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 @@ fill_it:
          * 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 @@ ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
         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 @@ ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
                 .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 @@ ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
                 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 @@ ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
         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 @@ ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
         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 @@ int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
                 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 @@ out_release:
          * 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 long do_splice(struct file *in, loff_t __user *off_in,
  */
 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 @@ static int get_iovec_page_array(const struct iovec __user *iov,
                         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 @@ static int get_iovec_page_array(const struct iovec __user *iov,
                  * 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 @@ static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
                              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 @@ static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
                 .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 (splice_grow_spd(pipe, &spd))
+                return -ENOMEM;
+
+        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)
-                return spd.nr_pages;
+                ret = spd.nr_pages;
+        else
+                ret = splice_to_pipe(pipe, &spd);
 
-        return splice_to_pipe(pipe, &spd);
+        splice_shrink_spd(pipe, &spd);
+        return ret;
 }
 
 /*
@@ -1738,13 +1797,13 @@ static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
          * 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 @@ retry:
                  * 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 @@ retry:
                 }
 
                 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 @@ retry:
                         *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 @@ static int link_pipe(struct pipe_inode_info *ipipe,
                  * 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,