[PATCH 1/2] Revert "iov_iter: Kill ITER_PIPE"
From: Konrad Dybcio
Date: Wed Feb 15 2023 - 07:01:04 EST
Reverting this is a dependency for reverting commit d9722a475711
("splice: Do splice read from a buffered file without using ITER_PIPE")
This reverts commit 82cf0207bed44feb0b3b8b17a4c351fdde34a97b.
Signed-off-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxx>
---
fs/cifs/file.c | 8 +-
include/linux/uio.h | 14 ++
lib/iov_iter.c | 435 +++++++++++++++++++++++++++++++++++++++++++++++++++-
mm/filemap.c | 3 +-
4 files changed, 455 insertions(+), 5 deletions(-)
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 9e0c03be032b..052609172690 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -3833,7 +3833,13 @@ cifs_readdata_to_iov(struct cifs_readdata *rdata, struct iov_iter *iter)
size_t copy = min_t(size_t, remaining, PAGE_SIZE);
size_t written;
- written = copy_page_to_iter(page, 0, copy, iter);
+ if (unlikely(iov_iter_is_pipe(iter))) {
+ void *addr = kmap_atomic(page);
+
+ written = copy_to_iter(addr, copy, iter);
+ kunmap_atomic(addr);
+ } else
+ written = copy_page_to_iter(page, 0, copy, iter);
remaining -= written;
if (written < copy && iov_iter_count(iter) > 0)
break;
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 74598426edb4..27e3fd942960 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -11,6 +11,7 @@
#include <uapi/linux/uio.h>
struct page;
+struct pipe_inode_info;
typedef unsigned int __bitwise iov_iter_extraction_t;
@@ -24,6 +25,7 @@ enum iter_type {
ITER_IOVEC,
ITER_KVEC,
ITER_BVEC,
+ ITER_PIPE,
ITER_XARRAY,
ITER_DISCARD,
ITER_UBUF,
@@ -53,10 +55,15 @@ struct iov_iter {
const struct kvec *kvec;
const struct bio_vec *bvec;
struct xarray *xarray;
+ struct pipe_inode_info *pipe;
void __user *ubuf;
};
union {
unsigned long nr_segs;
+ struct {
+ unsigned int head;
+ unsigned int start_head;
+ };
loff_t xarray_start;
};
};
@@ -94,6 +101,11 @@ static inline bool iov_iter_is_bvec(const struct iov_iter *i)
return iov_iter_type(i) == ITER_BVEC;
}
+static inline bool iov_iter_is_pipe(const struct iov_iter *i)
+{
+ return iov_iter_type(i) == ITER_PIPE;
+}
+
static inline bool iov_iter_is_discard(const struct iov_iter *i)
{
return iov_iter_type(i) == ITER_DISCARD;
@@ -235,6 +247,8 @@ void iov_iter_kvec(struct iov_iter *i, unsigned int direction, const struct kvec
unsigned long nr_segs, size_t count);
void iov_iter_bvec(struct iov_iter *i, unsigned int direction, const struct bio_vec *bvec,
unsigned long nr_segs, size_t count);
+void iov_iter_pipe(struct iov_iter *i, unsigned int direction, struct pipe_inode_info *pipe,
+ size_t count);
void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count);
void iov_iter_xarray(struct iov_iter *i, unsigned int direction, struct xarray *xarray,
loff_t start, size_t count);
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index fad95e4cf372..02a73ca52207 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -14,6 +14,8 @@
#include <linux/scatterlist.h>
#include <linux/instrumented.h>
+#define PIPE_PARANOIA /* for now */
+
/* covers ubuf and kbuf alike */
#define iterate_buf(i, n, base, len, off, __p, STEP) { \
size_t __maybe_unused off = 0; \
@@ -184,6 +186,156 @@ static int copyin(void *to, const void __user *from, size_t n)
return res;
}
+static inline struct pipe_buffer *pipe_buf(const struct pipe_inode_info *pipe,
+ unsigned int slot)
+{
+ return &pipe->bufs[slot & (pipe->ring_size - 1)];
+}
+
+#ifdef PIPE_PARANOIA
+static bool sanity(const struct iov_iter *i)
+{
+ struct pipe_inode_info *pipe = i->pipe;
+ unsigned int p_head = pipe->head;
+ unsigned int p_tail = pipe->tail;
+ unsigned int p_occupancy = pipe_occupancy(p_head, p_tail);
+ unsigned int i_head = i->head;
+ unsigned int idx;
+
+ if (i->last_offset) {
+ struct pipe_buffer *p;
+ if (unlikely(p_occupancy == 0))
+ goto Bad; // pipe must be non-empty
+ if (unlikely(i_head != p_head - 1))
+ goto Bad; // must be at the last buffer...
+
+ p = pipe_buf(pipe, i_head);
+ if (unlikely(p->offset + p->len != abs(i->last_offset)))
+ goto Bad; // ... at the end of segment
+ } else {
+ if (i_head != p_head)
+ goto Bad; // must be right after the last buffer
+ }
+ return true;
+Bad:
+ printk(KERN_ERR "idx = %d, offset = %d\n", i_head, i->last_offset);
+ printk(KERN_ERR "head = %d, tail = %d, buffers = %d\n",
+ p_head, p_tail, pipe->ring_size);
+ for (idx = 0; idx < pipe->ring_size; idx++)
+ printk(KERN_ERR "[%p %p %d %d]\n",
+ pipe->bufs[idx].ops,
+ pipe->bufs[idx].page,
+ pipe->bufs[idx].offset,
+ pipe->bufs[idx].len);
+ WARN_ON(1);
+ return false;
+}
+#else
+#define sanity(i) true
+#endif
+
+static struct page *push_anon(struct pipe_inode_info *pipe, unsigned size)
+{
+ struct page *page = alloc_page(GFP_USER);
+ if (page) {
+ struct pipe_buffer *buf = pipe_buf(pipe, pipe->head++);
+ *buf = (struct pipe_buffer) {
+ .ops = &default_pipe_buf_ops,
+ .page = page,
+ .offset = 0,
+ .len = size
+ };
+ }
+ return page;
+}
+
+static void push_page(struct pipe_inode_info *pipe, struct page *page,
+ unsigned int offset, unsigned int size)
+{
+ struct pipe_buffer *buf = pipe_buf(pipe, pipe->head++);
+ *buf = (struct pipe_buffer) {
+ .ops = &page_cache_pipe_buf_ops,
+ .page = page,
+ .offset = offset,
+ .len = size
+ };
+ get_page(page);
+}
+
+static inline int last_offset(const struct pipe_buffer *buf)
+{
+ if (buf->ops == &default_pipe_buf_ops)
+ return buf->len; // buf->offset is 0 for those
+ else
+ return -(buf->offset + buf->len);
+}
+
+static struct page *append_pipe(struct iov_iter *i, size_t size,
+ unsigned int *off)
+{
+ struct pipe_inode_info *pipe = i->pipe;
+ int offset = i->last_offset;
+ struct pipe_buffer *buf;
+ struct page *page;
+
+ if (offset > 0 && offset < PAGE_SIZE) {
+ // some space in the last buffer; add to it
+ buf = pipe_buf(pipe, pipe->head - 1);
+ size = min_t(size_t, size, PAGE_SIZE - offset);
+ buf->len += size;
+ i->last_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->last_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)
+{
+ struct pipe_inode_info *pipe = i->pipe;
+ unsigned int head = pipe->head;
+
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+
+ if (unlikely(!bytes))
+ return 0;
+
+ if (!sanity(i))
+ return 0;
+
+ if (offset && i->last_offset == -offset) { // could we merge it?
+ struct pipe_buffer *buf = pipe_buf(pipe, head - 1);
+ if (buf->page == page) {
+ buf->len += bytes;
+ i->last_offset -= bytes;
+ i->count -= bytes;
+ return bytes;
+ }
+ }
+ if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
+ return 0;
+
+ push_page(pipe, page, offset, bytes);
+ i->last_offset = -(offset + bytes);
+ i->head = head;
+ i->count -= bytes;
+ return bytes;
+}
+
/*
* fault_in_iov_iter_readable - fault in iov iterator for reading
* @i: iterator
@@ -287,6 +439,46 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction,
}
EXPORT_SYMBOL(iov_iter_init);
+// returns the offset in partial buffer (if any)
+static inline unsigned int pipe_npages(const struct iov_iter *i, int *npages)
+{
+ struct pipe_inode_info *pipe = i->pipe;
+ int used = pipe->head - pipe->tail;
+ int off = i->last_offset;
+
+ *npages = max((int)pipe->max_usage - used, 0);
+
+ if (off > 0 && off < PAGE_SIZE) { // anon and not full
+ (*npages)++;
+ return off;
+ }
+ return 0;
+}
+
+static size_t copy_pipe_to_iter(const void *addr, size_t bytes,
+ struct iov_iter *i)
+{
+ unsigned int off, chunk;
+
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+ if (unlikely(!bytes))
+ return 0;
+
+ if (!sanity(i))
+ return 0;
+
+ 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;
+ }
+ return bytes;
+}
+
static __wsum csum_and_memcpy(void *to, const void *from, size_t len,
__wsum sum, size_t off)
{
@@ -294,10 +486,44 @@ static __wsum csum_and_memcpy(void *to, const void *from, size_t len,
return csum_block_add(sum, next, off);
}
+static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes,
+ struct iov_iter *i, __wsum *sump)
+{
+ __wsum sum = *sump;
+ size_t off = 0;
+ unsigned int chunk, r;
+
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+ if (unlikely(!bytes))
+ return 0;
+
+ if (!sanity(i))
+ return 0;
+
+ while (bytes) {
+ 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);
+ off += chunk;
+ bytes -= chunk;
+ }
+ *sump = sum;
+ return off;
+}
+
size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
{
if (WARN_ON_ONCE(i->data_source))
return 0;
+ if (unlikely(iov_iter_is_pipe(i)))
+ return copy_pipe_to_iter(addr, bytes, i);
if (user_backed_iter(i))
might_fault();
iterate_and_advance(i, bytes, base, len, off,
@@ -319,6 +545,42 @@ static int copyout_mc(void __user *to, const void *from, size_t n)
return n;
}
+static size_t copy_mc_pipe_to_iter(const void *addr, size_t bytes,
+ struct iov_iter *i)
+{
+ 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;
+
+ 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);
+ xfer += chunk;
+ bytes -= chunk;
+ if (rem) {
+ iov_iter_revert(i, rem);
+ break;
+ }
+ }
+ return xfer;
+}
+
/**
* _copy_mc_to_iter - copy to iter with source memory error exception handling
* @addr: source kernel address
@@ -338,8 +600,9 @@ static int copyout_mc(void __user *to, const void *from, size_t n)
* alignment and poison alignment assumptions to avoid re-triggering
* hardware exceptions.
*
- * * ITER_KVEC and ITER_BVEC can return short copies. Compare to
- * copy_to_iter() where only ITER_IOVEC attempts might return a short copy.
+ * * ITER_KVEC, ITER_PIPE, and ITER_BVEC can return short copies.
+ * Compare to copy_to_iter() where only ITER_IOVEC attempts might return
+ * a short copy.
*
* Return: number of bytes copied (may be %0)
*/
@@ -347,6 +610,8 @@ size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
{
if (WARN_ON_ONCE(i->data_source))
return 0;
+ if (unlikely(iov_iter_is_pipe(i)))
+ return copy_mc_pipe_to_iter(addr, bytes, i);
if (user_backed_iter(i))
might_fault();
__iterate_and_advance(i, bytes, base, len, off,
@@ -452,6 +717,8 @@ size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
return 0;
if (WARN_ON_ONCE(i->data_source))
return 0;
+ if (unlikely(iov_iter_is_pipe(i)))
+ return copy_page_to_iter_pipe(page, offset, bytes, i);
page += offset / PAGE_SIZE; // first subpage
offset %= PAGE_SIZE;
while (1) {
@@ -500,8 +767,36 @@ size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
}
EXPORT_SYMBOL(copy_page_from_iter);
+static size_t pipe_zero(size_t bytes, struct iov_iter *i)
+{
+ unsigned int chunk, off;
+
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+ if (unlikely(!bytes))
+ return 0;
+
+ if (!sanity(i))
+ return 0;
+
+ 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);
+ }
+ return bytes;
+}
+
size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
{
+ if (unlikely(iov_iter_is_pipe(i)))
+ return pipe_zero(bytes, i);
iterate_and_advance(i, bytes, base, len, count,
clear_user(base, len),
memset(base, 0, len)
@@ -532,6 +827,32 @@ size_t copy_page_from_iter_atomic(struct page *page, unsigned offset, size_t byt
}
EXPORT_SYMBOL(copy_page_from_iter_atomic);
+static void pipe_advance(struct iov_iter *i, size_t size)
+{
+ struct pipe_inode_info *pipe = i->pipe;
+ int off = i->last_offset;
+
+ if (!off && !size) {
+ pipe_discard_from(pipe, i->start_head); // discard everything
+ return;
+ }
+ i->count -= size;
+ while (1) {
+ struct pipe_buffer *buf = pipe_buf(pipe, i->head);
+ if (off) /* make it relative to the beginning of buffer */
+ size += abs(off) - buf->offset;
+ if (size <= buf->len) {
+ buf->len = size;
+ i->last_offset = last_offset(buf);
+ break;
+ }
+ size -= buf->len;
+ i->head++;
+ off = 0;
+ }
+ pipe_discard_from(pipe, i->head + 1); // discard everything past this one
+}
+
static void iov_iter_bvec_advance(struct iov_iter *i, size_t size)
{
const struct bio_vec *bvec, *end;
@@ -583,6 +904,8 @@ void iov_iter_advance(struct iov_iter *i, size_t size)
iov_iter_iovec_advance(i, size);
} else if (iov_iter_is_bvec(i)) {
iov_iter_bvec_advance(i, size);
+ } else if (iov_iter_is_pipe(i)) {
+ pipe_advance(i, size);
} else if (iov_iter_is_discard(i)) {
i->count -= size;
}
@@ -596,6 +919,26 @@ void iov_iter_revert(struct iov_iter *i, size_t unroll)
if (WARN_ON(unroll > MAX_RW_COUNT))
return;
i->count += unroll;
+ if (unlikely(iov_iter_is_pipe(i))) {
+ struct pipe_inode_info *pipe = i->pipe;
+ unsigned int head = pipe->head;
+
+ while (head > i->start_head) {
+ struct pipe_buffer *b = pipe_buf(pipe, --head);
+ if (unroll < b->len) {
+ b->len -= unroll;
+ i->last_offset = last_offset(b);
+ i->head = head;
+ return;
+ }
+ unroll -= b->len;
+ pipe_buf_release(pipe, b);
+ pipe->head--;
+ }
+ i->last_offset = 0;
+ i->head = head;
+ return;
+ }
if (unlikely(iov_iter_is_discard(i)))
return;
if (unroll <= i->iov_offset) {
@@ -683,6 +1026,24 @@ void iov_iter_bvec(struct iov_iter *i, unsigned int direction,
}
EXPORT_SYMBOL(iov_iter_bvec);
+void iov_iter_pipe(struct iov_iter *i, unsigned int direction,
+ struct pipe_inode_info *pipe,
+ size_t count)
+{
+ BUG_ON(direction != READ);
+ WARN_ON(pipe_full(pipe->head, pipe->tail, pipe->ring_size));
+ *i = (struct iov_iter){
+ .iter_type = ITER_PIPE,
+ .data_source = false,
+ .pipe = pipe,
+ .head = pipe->head,
+ .start_head = pipe->head,
+ .last_offset = 0,
+ .count = count
+ };
+}
+EXPORT_SYMBOL(iov_iter_pipe);
+
/**
* iov_iter_xarray - Initialise an I/O iterator to use the pages in an xarray
* @i: The iterator to initialise.
@@ -807,6 +1168,19 @@ bool iov_iter_is_aligned(const struct iov_iter *i, unsigned addr_mask,
if (iov_iter_is_bvec(i))
return iov_iter_aligned_bvec(i, addr_mask, len_mask);
+ if (iov_iter_is_pipe(i)) {
+ size_t size = i->count;
+
+ if (size & len_mask)
+ return false;
+ if (size && i->last_offset > 0) {
+ if (i->last_offset & addr_mask)
+ return false;
+ }
+
+ return true;
+ }
+
if (iov_iter_is_xarray(i)) {
if (i->count & len_mask)
return false;
@@ -876,6 +1250,14 @@ unsigned long iov_iter_alignment(const struct iov_iter *i)
if (iov_iter_is_bvec(i))
return iov_iter_alignment_bvec(i);
+ if (iov_iter_is_pipe(i)) {
+ size_t size = i->count;
+
+ if (size && i->last_offset > 0)
+ return size | i->last_offset;
+ return size;
+ }
+
if (iov_iter_is_xarray(i))
return (i->xarray_start + i->iov_offset) | i->count;
@@ -927,6 +1309,36 @@ static int want_pages_array(struct page ***res, size_t size,
return count;
}
+static ssize_t pipe_get_pages(struct iov_iter *i,
+ struct page ***pages, size_t maxsize, unsigned maxpages,
+ size_t *start)
+{
+ unsigned int npages, count, off, chunk;
+ struct page **p;
+ size_t left;
+
+ if (!sanity(i))
+ return -EFAULT;
+
+ *start = off = pipe_npages(i, &npages);
+ if (!npages)
+ return -EFAULT;
+ count = want_pages_array(pages, maxsize, off, min(npages, maxpages));
+ if (!count)
+ return -ENOMEM;
+ p = *pages;
+ for (npages = 0, left = maxsize ; npages < count; npages++, left -= chunk) {
+ struct page *page = append_pipe(i, left, &off);
+ if (!page)
+ break;
+ chunk = min_t(size_t, left, PAGE_SIZE - off);
+ get_page(*p++ = page);
+ }
+ if (!npages)
+ return -EFAULT;
+ return maxsize - left;
+}
+
static ssize_t iter_xarray_populate_pages(struct page **pages, struct xarray *xa,
pgoff_t index, unsigned int nr_pages)
{
@@ -1076,6 +1488,8 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
}
return maxsize;
}
+ if (iov_iter_is_pipe(i))
+ return pipe_get_pages(i, pages, maxsize, maxpages, start);
if (iov_iter_is_xarray(i))
return iter_xarray_get_pages(i, pages, maxsize, maxpages, start);
return -EFAULT;
@@ -1165,7 +1579,9 @@ size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
}
sum = csum_shift(csstate->csum, csstate->off);
- iterate_and_advance(i, bytes, base, len, off, ({
+ if (unlikely(iov_iter_is_pipe(i)))
+ bytes = csum_and_copy_to_pipe_iter(addr, bytes, i, &sum);
+ else iterate_and_advance(i, bytes, base, len, off, ({
next = csum_and_copy_to_user(addr + off, base, len);
sum = csum_block_add(sum, next, off);
next ? 0 : len;
@@ -1250,6 +1666,15 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages)
return iov_npages(i, maxpages);
if (iov_iter_is_bvec(i))
return bvec_npages(i, maxpages);
+ if (iov_iter_is_pipe(i)) {
+ int npages;
+
+ if (!sanity(i))
+ return 0;
+
+ pipe_npages(i, &npages);
+ return min(npages, maxpages);
+ }
if (iov_iter_is_xarray(i)) {
unsigned offset = (i->xarray_start + i->iov_offset) % PAGE_SIZE;
int npages = DIV_ROUND_UP(offset + i->count, PAGE_SIZE);
@@ -1262,6 +1687,10 @@ EXPORT_SYMBOL(iov_iter_npages);
const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
{
*new = *old;
+ if (unlikely(iov_iter_is_pipe(new))) {
+ WARN_ON(1);
+ return NULL;
+ }
if (iov_iter_is_bvec(new))
return new->bvec = kmemdup(new->bvec,
new->nr_segs * sizeof(struct bio_vec),
diff --git a/mm/filemap.c b/mm/filemap.c
index d647b2e7cd51..9cf984f7c25e 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2692,7 +2692,8 @@ ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter,
if (unlikely(iocb->ki_pos >= i_size_read(inode)))
break;
- error = filemap_get_pages(iocb, iter->count, &fbatch, false);
+ error = filemap_get_pages(iocb, iter->count, &fbatch,
+ iov_iter_is_pipe(iter));
if (error < 0)
break;
--
2.39.1