@@ -3806,13 +3806,7 @@ 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;
- 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);
+ written = copy_page_to_iter(page, 0, copy, iter);
remaining -= written;
if (written < copy && iov_iter_count(iter) > 0)
break;
@@ -11,7 +11,6 @@
#include <uapi/linux/uio.h>
struct page;
-struct pipe_inode_info;
typedef unsigned int __bitwise iov_iter_extraction_t;
@@ -25,7 +24,6 @@ enum iter_type {
ITER_IOVEC,
ITER_KVEC,
ITER_BVEC,
- ITER_PIPE,
ITER_XARRAY,
ITER_DISCARD,
ITER_UBUF,
@@ -55,15 +53,10 @@ 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;
};
};
@@ -101,11 +94,6 @@ 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;
@@ -247,8 +235,6 @@ 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);
@@ -14,8 +14,6 @@
#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; \
@@ -186,156 +184,6 @@ 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
@@ -439,46 +287,6 @@ 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)
{
@@ -486,44 +294,10 @@ 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,
@@ -545,42 +319,6 @@ 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
@@ -600,9 +338,8 @@ static size_t copy_mc_pipe_to_iter(const void *addr, size_t bytes,
* alignment and poison alignment assumptions to avoid re-triggering
* hardware exceptions.
*
- * * 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.
+ * * ITER_KVEC 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)
*/
@@ -610,8 +347,6 @@ 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,
@@ -717,8 +452,6 @@ 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) {
@@ -767,36 +500,8 @@ 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)
@@ -827,32 +532,6 @@ 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;
@@ -904,8 +583,6 @@ 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;
}
@@ -919,26 +596,6 @@ 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) {
@@ -1026,24 +683,6 @@ 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.
@@ -1168,19 +807,6 @@ 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;
@@ -1250,14 +876,6 @@ 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;
@@ -1309,36 +927,6 @@ 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)
{
@@ -1488,8 +1076,6 @@ 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;
@@ -1579,9 +1165,7 @@ size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
}
sum = csum_shift(csstate->csum, csstate->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, ({
+ 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;
@@ -1666,15 +1250,6 @@ 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);
@@ -1687,10 +1262,6 @@ 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),
@@ -1917,53 +1488,6 @@ void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state)
i->nr_segs = state->nr_segs;
}
-/*
- * Extract a list of contiguous pages from an ITER_PIPE iterator. This does
- * not get references of its own on the pages, nor does it get a pin on them.
- * If there's a partial page, it adds that first and will then allocate and add
- * pages into the pipe to make up the buffer space to the amount required.
- *
- * The caller must hold the pipe locked and only transferring into a pipe is
- * supported.
- */
-static ssize_t iov_iter_extract_pipe_pages(struct iov_iter *i,
- struct page ***pages, size_t maxsize,
- unsigned int maxpages,
- iov_iter_extraction_t extraction_flags,
- size_t *offset0)
-{
- unsigned int nr, offset, chunk, j;
- struct page **p;
- size_t left;
-
- if (!sanity(i))
- return -EFAULT;
-
- offset = pipe_npages(i, &nr);
- if (!nr)
- return -EFAULT;
- *offset0 = offset;
-
- maxpages = min_t(size_t, nr, maxpages);
- maxpages = want_pages_array(pages, maxsize, offset, maxpages);
- if (!maxpages)
- return -ENOMEM;
- p = *pages;
-
- left = maxsize;
- for (j = 0; j < maxpages; j++) {
- struct page *page = append_pipe(i, left, &offset);
- if (!page)
- break;
- chunk = min_t(size_t, left, PAGE_SIZE - offset);
- left -= chunk;
- *p++ = page;
- }
- if (!j)
- return -EFAULT;
- return maxsize - left;
-}
-
/*
* Extract a list of contiguous pages from an ITER_XARRAY iterator. This does not
* get references on the pages, nor does it get a pin on them.
@@ -2184,12 +1708,6 @@ static ssize_t iov_iter_extract_user_pages(struct iov_iter *i,
* added to the pages, but refs will not be taken.
* iov_iter_extract_will_pin() will return true.
*
- * (*) If the iterator is ITER_PIPE, this must describe a destination for the
- * data. Additional pages may be allocated and added to the pipe (which
- * will hold the refs), but pins will not be obtained for the caller. The
- * caller must hold the pipe lock. iov_iter_extract_will_pin() will
- * return false.
- *
* (*) If the iterator is ITER_KVEC, ITER_BVEC or ITER_XARRAY, the pages are
* merely listed; no extra refs or pins are obtained.
* iov_iter_extract_will_pin() will return 0.
@@ -2226,10 +1744,6 @@ ssize_t iov_iter_extract_pages(struct iov_iter *i,
return iov_iter_extract_bvec_pages(i, pages, maxsize,
maxpages, extraction_flags,
offset0);
- if (iov_iter_is_pipe(i))
- return iov_iter_extract_pipe_pages(i, pages, maxsize,
- maxpages, extraction_flags,
- offset0);
if (iov_iter_is_xarray(i))
return iov_iter_extract_xarray_pages(i, pages, maxsize,
maxpages, extraction_flags,
@@ -2446,9 +2446,6 @@ static bool filemap_range_uptodate(struct address_space *mapping,
if (folio_test_uptodate(folio))
return true;
- /* pipes can't handle partially uptodate pages */
- if (iov_iter_is_pipe(iter))
- return false;
if (!mapping->a_ops->is_partially_uptodate)
return false;
if (mapping->host->i_blkbits >= folio_shift(folio))