From 8fad7767edcfd3f93e0d9985cb2dc1db270b8719 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Tue, 14 Jun 2022 13:53:53 -0400 Subject: ITER_PIPE: allocate buffers as we go in copy-to-pipe primitives New helper: append_pipe(). Extends the last buffer if possible, allocates a new one otherwise. Returns page and offset in it on success, NULL on failure. iov_iter is advanced past the data we've got. Use that instead of push_pipe() in copy-to-pipe primitives; they get simpler that way. Handling of short copy (in "mc" one) is done simply by iov_iter_revert() - iov_iter is in consistent state after that one, so we can use that. [Fix for braino caught by Liu Xinpeng folded in] [another braino fix, this time in copy_pipe_to_iter() and pipe_zero(); caught by testcase from Hugh Dickins] Signed-off-by: Al Viro --- lib/iov_iter.c | 171 +++++++++++++++++++++++++++++++++------------------------ 1 file changed, 98 insertions(+), 73 deletions(-) (limited to 'lib') diff --git a/lib/iov_iter.c b/lib/iov_iter.c index a5c436e564e8..e22c272cb420 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -259,6 +259,45 @@ static void push_page(struct pipe_inode_info *pipe, struct page *page, get_page(page); } +static inline bool allocated(struct pipe_buffer *buf) +{ + return buf->ops == &default_pipe_buf_ops; +} + +static struct page *append_pipe(struct iov_iter *i, size_t size, + unsigned int *off) +{ + struct pipe_inode_info *pipe = i->pipe; + size_t offset = i->iov_offset; + struct pipe_buffer *buf; + struct page *page; + + if (offset && offset < PAGE_SIZE) { + // some space in the last buffer; can we add to it? + buf = pipe_buf(pipe, pipe->head - 1); + if (allocated(buf)) { + size = min_t(size_t, size, PAGE_SIZE - offset); + buf->len += size; + i->iov_offset += size; + i->count -= size; + *off = offset; + return buf->page; + } + } + // OK, we need a new buffer + *off = 0; + size = min_t(size_t, size, PAGE_SIZE); + if (pipe_full(pipe->head, pipe->tail, pipe->max_usage)) + return NULL; + page = push_anon(pipe, size); + if (!page) + return NULL; + i->head = pipe->head - 1; + i->iov_offset = size; + i->count -= size; + return page; +} + static size_t copy_page_to_iter_pipe(struct page *page, size_t offset, size_t bytes, struct iov_iter *i) { @@ -396,11 +435,6 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction, } EXPORT_SYMBOL(iov_iter_init); -static inline bool allocated(struct pipe_buffer *buf) -{ - return buf->ops == &default_pipe_buf_ops; -} - static inline void data_start(const struct iov_iter *i, unsigned int *iter_headp, size_t *offp) { @@ -459,28 +493,24 @@ static size_t push_pipe(struct iov_iter *i, size_t size, static size_t copy_pipe_to_iter(const void *addr, size_t bytes, struct iov_iter *i) { - struct pipe_inode_info *pipe = i->pipe; - unsigned int p_mask = pipe->ring_size - 1; - unsigned int i_head; - size_t n, off; + unsigned int off, chunk; - if (!sanity(i)) + if (unlikely(bytes > i->count)) + bytes = i->count; + if (unlikely(!bytes)) return 0; - bytes = n = push_pipe(i, bytes, &i_head, &off); - if (unlikely(!n)) + if (!sanity(i)) return 0; - do { - size_t chunk = min_t(size_t, n, PAGE_SIZE - off); - memcpy_to_page(pipe->bufs[i_head & p_mask].page, off, addr, chunk); - i->head = i_head; - i->iov_offset = off + chunk; - n -= chunk; + + for (size_t n = bytes; n; n -= chunk) { + struct page *page = append_pipe(i, n, &off); + chunk = min_t(size_t, n, PAGE_SIZE - off); + if (!page) + return bytes - n; + memcpy_to_page(page, off, addr, chunk); addr += chunk; - off = 0; - i_head++; - } while (n); - i->count -= bytes; + } return bytes; } @@ -494,31 +524,32 @@ static __wsum csum_and_memcpy(void *to, const void *from, size_t len, static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes, struct iov_iter *i, __wsum *sump) { - struct pipe_inode_info *pipe = i->pipe; - unsigned int p_mask = pipe->ring_size - 1; __wsum sum = *sump; size_t off = 0; - unsigned int i_head; - size_t r; + unsigned int chunk, r; + + if (unlikely(bytes > i->count)) + bytes = i->count; + if (unlikely(!bytes)) + return 0; if (!sanity(i)) return 0; - bytes = push_pipe(i, bytes, &i_head, &r); while (bytes) { - size_t chunk = min_t(size_t, bytes, PAGE_SIZE - r); - char *p = kmap_local_page(pipe->bufs[i_head & p_mask].page); + struct page *page = append_pipe(i, bytes, &r); + char *p; + + if (!page) + break; + chunk = min_t(size_t, bytes, PAGE_SIZE - r); + p = kmap_local_page(page); sum = csum_and_memcpy(p + r, addr + off, chunk, sum, off); kunmap_local(p); - i->head = i_head; - i->iov_offset = r + chunk; - bytes -= chunk; off += chunk; - r = 0; - i_head++; + bytes -= chunk; } *sump = sum; - i->count -= off; return off; } @@ -550,39 +581,36 @@ static int copyout_mc(void __user *to, const void *from, size_t n) static size_t copy_mc_pipe_to_iter(const void *addr, size_t bytes, struct iov_iter *i) { - struct pipe_inode_info *pipe = i->pipe; - unsigned int p_mask = pipe->ring_size - 1; - unsigned int i_head; - unsigned int valid = pipe->head; - size_t n, off, xfer = 0; + size_t xfer = 0; + unsigned int off, chunk; + + if (unlikely(bytes > i->count)) + bytes = i->count; + if (unlikely(!bytes)) + return 0; if (!sanity(i)) return 0; - n = push_pipe(i, bytes, &i_head, &off); - while (n) { - size_t chunk = min_t(size_t, n, PAGE_SIZE - off); - char *p = kmap_local_page(pipe->bufs[i_head & p_mask].page); + while (bytes) { + struct page *page = append_pipe(i, bytes, &off); unsigned long rem; + char *p; + + if (!page) + break; + chunk = min_t(size_t, bytes, PAGE_SIZE - off); + p = kmap_local_page(page); rem = copy_mc_to_kernel(p + off, addr + xfer, chunk); chunk -= rem; kunmap_local(p); - if (chunk) { - i->head = i_head; - i->iov_offset = off + chunk; - xfer += chunk; - valid = i_head + 1; - } + xfer += chunk; + bytes -= chunk; if (rem) { - pipe->bufs[i_head & p_mask].len -= rem; - pipe_discard_from(pipe, valid); + iov_iter_revert(i, rem); break; } - n -= chunk; - off = 0; - i_head++; } - i->count -= xfer; return xfer; } @@ -769,30 +797,27 @@ EXPORT_SYMBOL(copy_page_from_iter); static size_t pipe_zero(size_t bytes, struct iov_iter *i) { - struct pipe_inode_info *pipe = i->pipe; - unsigned int p_mask = pipe->ring_size - 1; - unsigned int i_head; - size_t n, off; + unsigned int chunk, off; - if (!sanity(i)) + if (unlikely(bytes > i->count)) + bytes = i->count; + if (unlikely(!bytes)) return 0; - bytes = n = push_pipe(i, bytes, &i_head, &off); - if (unlikely(!n)) + if (!sanity(i)) return 0; - do { - size_t chunk = min_t(size_t, n, PAGE_SIZE - off); - char *p = kmap_local_page(pipe->bufs[i_head & p_mask].page); + for (size_t n = bytes; n; n -= chunk) { + struct page *page = append_pipe(i, n, &off); + char *p; + + if (!page) + return bytes - n; + chunk = min_t(size_t, n, PAGE_SIZE - off); + p = kmap_local_page(page); memset(p + off, 0, chunk); kunmap_local(p); - i->head = i_head; - i->iov_offset = off + chunk; - n -= chunk; - off = 0; - i_head++; - } while (n); - i->count -= bytes; + } return bytes; } -- cgit v1.2.3