diff options
| author | Al Viro <viro@zeniv.linux.org.uk> | 2021-04-29 20:42:25 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-07-14 17:06:06 +0200 |
| commit | 3854f9c612ae54295b076a478591b5e5987d52d4 (patch) | |
| tree | 6face1ace443602c050b7822242d21cf2a66a54d /lib | |
| parent | 64c430ea07a40dba6a277f3e9518d174269d1542 (diff) | |
teach copy_page_to_iter() to handle compound pages
commit 08aa64796016cb47b2ef3d0924653b4d944b0d65 upstream.
In situation when copy_page_to_iter() got a compound page the current
code would only work on systems with no CONFIG_HIGHMEM. It *is* the majority
of real-world setups, or we would've drown in bug reports by now. Still needs
fixing.
Current variant works for solitary page; rename that to
__copy_page_to_iter() and turn the handling of compound pages into a loop over
subpages.
Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/iov_iter.c | 28 |
1 files changed, 25 insertions, 3 deletions
diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 0ce968a0060b..f4376d30d6ee 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -957,11 +957,9 @@ static inline bool page_copy_sane(struct page *page, size_t offset, size_t n) return false; } -size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes, +static size_t __copy_page_to_iter(struct page *page, size_t offset, size_t bytes, struct iov_iter *i) { - if (unlikely(!page_copy_sane(page, offset, bytes))) - return 0; if (i->type & (ITER_BVEC | ITER_KVEC | ITER_XARRAY)) { void *kaddr = kmap_atomic(page); size_t wanted = copy_to_iter(kaddr + offset, bytes, i); @@ -977,6 +975,30 @@ size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes, else return copy_page_to_iter_pipe(page, offset, bytes, i); } + +size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes, + struct iov_iter *i) +{ + size_t res = 0; + if (unlikely(!page_copy_sane(page, offset, bytes))) + return 0; + page += offset / PAGE_SIZE; // first subpage + offset %= PAGE_SIZE; + while (1) { + size_t n = __copy_page_to_iter(page, offset, + min(bytes, (size_t)PAGE_SIZE - offset), i); + res += n; + bytes -= n; + if (!bytes || !n) + break; + offset += n; + if (offset == PAGE_SIZE) { + page++; + offset = 0; + } + } + return res; +} EXPORT_SYMBOL(copy_page_to_iter); size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes, |