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iov_iter: replace iov_iter_copy_from_user_atomic() with iterator-advancing variant 

Replacement is called copy_page_from_iter_atomic(); unlike the old primitive the
callers do *not* need to do iov_iter_advance() after it.  In case when they end
up consuming less than they'd been given they need to do iov_iter_revert() on
everything they had not consumed.  That, however, needs to be done only on slow
paths.

All in-tree callers converted.  And that kills the last user of iterate_all_kinds()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2021-04-30 10:26:41 -04:00
parent e4f8df8679
commit f0b65f39ac
8 changed files with 43 additions and 60 deletions
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9
Documentation/filesystems/porting.rst
View File

@ -890,3 +890,12 @@ been called or returned with non -EIOCBQUEUED code.
mnt_want_write_file() can now only be paired with mnt_drop_write_file(),
whereas previously it could be paired with mnt_drop_write() as well.
---
**mandatory**
iov_iter_copy_from_user_atomic() is gone; use copy_page_from_iter_atomic().
The difference is copy_page_from_iter_atomic() advances the iterator and
you don't need iov_iter_advance() after it. However, if you decide to use
only a part of obtained data, you should do iov_iter_revert().

23
fs/btrfs/file.c
View File

@ -398,7 +398,7 @@ static noinline int btrfs_copy_from_user(loff_t pos, size_t write_bytes,
/*
* Copy data from userspace to the current page
*/
copied = iov_iter_copy_from_user_atomic(page, i, offset, count);
copied = copy_page_from_iter_atomic(page, offset, count, i);
/* Flush processor's dcache for this page */
flush_dcache_page(page);
@ -412,20 +412,19 @@ static noinline int btrfs_copy_from_user(loff_t pos, size_t write_bytes,
* The rest of the btrfs_file_write code will fall
* back to page at a time copies after we return 0.
*/
if (!PageUptodate(page) && copied < count)
copied = 0;
if (unlikely(copied < count)) {
if (!PageUptodate(page)) {
iov_iter_revert(i, copied);
copied = 0;
}
if (!copied)
break;
}
iov_iter_advance(i, copied);
write_bytes -= copied;
total_copied += copied;
/* Return to btrfs_file_write_iter to fault page */
if (unlikely(copied == 0))
break;
if (copied < PAGE_SIZE - offset) {
offset += copied;
} else {
offset += copied;
if (offset == PAGE_SIZE) {
pg++;
offset = 0;
}

3
fs/fuse/file.c
View File

@ -1171,10 +1171,9 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
if (mapping_writably_mapped(mapping))
flush_dcache_page(page);
tmp = iov_iter_copy_from_user_atomic(page, ii, offset, bytes);
tmp = copy_page_from_iter_atomic(page, offset, bytes, ii);
flush_dcache_page(page);
iov_iter_advance(ii, tmp);
if (!tmp) {
unlock_page(page);
put_page(page);

14
fs/iomap/buffered-io.c
View File

@ -785,13 +785,15 @@ iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
if (mapping_writably_mapped(inode->i_mapping))
flush_dcache_page(page);
copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
copied = copy_page_from_iter_atomic(page, offset, bytes, i);
status = iomap_write_end(inode, pos, bytes, copied, page, iomap,
srcmap);
cond_resched();
if (unlikely(copied != status))
iov_iter_revert(i, copied - status);
cond_resched();
if (unlikely(status == 0)) {
/*
* A short copy made iomap_write_end() reject the
@ -803,11 +805,9 @@ iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
bytes = copied;
goto again;
}
copied = status;
iov_iter_advance(i, copied);
pos += copied;
written += copied;
length -= copied;
pos += status;
written += status;
length -= status;
balance_dirty_pages_ratelimited(inode->i_mapping);
} while (iov_iter_count(i) && length);

4
fs/ntfs/file.c
View File

@ -1690,9 +1690,7 @@ static size_t ntfs_copy_from_user_iter(struct page **pages, unsigned nr_pages,
len = PAGE_SIZE - ofs;
if (len > bytes)
len = bytes;
copied = iov_iter_copy_from_user_atomic(*pages, i, ofs,
len);
iov_iter_advance(i, copied);
copied = copy_page_from_iter_atomic(*pages, ofs, len, i);
total += copied;
bytes -= copied;
if (!bytes)

4
include/linux/uio.h
View File

@ -115,8 +115,8 @@ static inline struct iovec iov_iter_iovec(const struct iov_iter *iter)
};
}
size_t iov_iter_copy_from_user_atomic(struct page *page,
struct iov_iter *i, unsigned long offset, size_t bytes);
size_t copy_page_from_iter_atomic(struct page *page, unsigned offset,
size_t bytes, struct iov_iter *i);
void iov_iter_advance(struct iov_iter *i, size_t bytes);
void iov_iter_revert(struct iov_iter *i, size_t bytes);
int iov_iter_fault_in_readable(const struct iov_iter *i, size_t bytes);

30
lib/iov_iter.c
View File

@ -114,28 +114,6 @@
n = wanted - n; \
}
#define iterate_all_kinds(i, n, v, I, B, K, X) { \
if (likely(n)) { \
size_t skip = i->iov_offset; \
if (likely(iter_is_iovec(i))) { \
const struct iovec *iov; \
struct iovec v; \
iterate_iovec(i, n, v, iov, skip, (I)) \
} else if (iov_iter_is_bvec(i)) { \
struct bio_vec v; \
struct bvec_iter __bi; \
iterate_bvec(i, n, v, __bi, skip, (B)) \
} else if (iov_iter_is_kvec(i)) { \
const struct kvec *kvec; \
struct kvec v; \
iterate_kvec(i, n, v, kvec, skip, (K)) \
} else if (iov_iter_is_xarray(i)) { \
struct bio_vec v; \
iterate_xarray(i, n, v, skip, (X)); \
} \
} \
}
#define iterate_and_advance(i, n, v, I, B, K, X) { \
if (unlikely(i->count < n)) \
n = i->count; \
@ -1009,8 +987,8 @@ size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
}
EXPORT_SYMBOL(iov_iter_zero);
size_t iov_iter_copy_from_user_atomic(struct page *page,
struct iov_iter *i, unsigned long offset, size_t bytes)
size_t copy_page_from_iter_atomic(struct page *page, unsigned offset, size_t bytes,
struct iov_iter *i)
{
char *kaddr = kmap_atomic(page), *p = kaddr + offset;
if (unlikely(!page_copy_sane(page, offset, bytes))) {
@ -1022,7 +1000,7 @@ size_t iov_iter_copy_from_user_atomic(struct page *page,
WARN_ON(1);
return 0;
}
iterate_all_kinds(i, bytes, v,
iterate_and_advance(i, bytes, v,
copyin((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
memcpy_from_page((p += v.bv_len) - v.bv_len, v.bv_page,
v.bv_offset, v.bv_len),
@ -1033,7 +1011,7 @@ size_t iov_iter_copy_from_user_atomic(struct page *page,
kunmap_atomic(kaddr);
return bytes;
}
EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
EXPORT_SYMBOL(copy_page_from_iter_atomic);
static inline void pipe_truncate(struct iov_iter *i)
{

16
mm/filemap.c
View File

@ -3661,14 +3661,16 @@ ssize_t generic_perform_write(struct file *file,
if (mapping_writably_mapped(mapping))
flush_dcache_page(page);
copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
copied = copy_page_from_iter_atomic(page, offset, bytes, i);
flush_dcache_page(page);
status = a_ops->write_end(file, mapping, pos, bytes, copied,
page, fsdata);
if (unlikely(status < 0))
break;
if (unlikely(status != copied)) {
iov_iter_revert(i, copied - max(status, 0L));
if (unlikely(status < 0))
break;
}
cond_resched();
if (unlikely(status == 0)) {
@ -3682,10 +3684,8 @@ ssize_t generic_perform_write(struct file *file,
bytes = copied;
goto again;
}
copied = status;
iov_iter_advance(i, copied);
pos += copied;
written += copied;
pos += status;
written += status;
balance_dirty_pages_ratelimited(mapping);
} while (iov_iter_count(i));