From 581f9a2ac5a5ebd4f8dacae0077a5c723b50a868 Mon Sep 17 00:00:00 2001 From: Zach Brown Date: Fri, 14 Jun 2013 15:54:14 -0500 Subject: [PATCH] iov_iter: add a shorten call The generic direct write path wants to shorten its memory vector. It does this when it finds that it has to perform a partial write due to LIMIT_FSIZE. .direct_IO() always performs IO on all of the referenced memory because it doesn't have an argument to specify the length of the IO. We add an iov_iter operation for this so that the generic path can ask to shorten the memory vector without having to know what kind it is. We're happy to shorten the kernel copy of the iovec array, but we refuse to shorten the bio_vec array and return an error in this case. Signed-off-by: Dave Kleikamp Cc: Zach Brown --- fs/iov-iter.c | 15 +++++++++++++++ include/linux/fs.h | 5 +++++ 2 files changed, 20 insertions(+) diff --git a/fs/iov-iter.c b/fs/iov-iter.c index 5624e367f760..ec461c8fea22 100644 --- a/fs/iov-iter.c +++ b/fs/iov-iter.c @@ -226,6 +226,11 @@ static size_t ii_bvec_single_seg_count(const struct iov_iter *i) return min(i->count, bvec->bv_len - i->iov_offset); } +static int ii_bvec_shorten(struct iov_iter *i, size_t count) +{ + return -EINVAL; +} + struct iov_iter_ops ii_bvec_ops = { .ii_copy_to_user_atomic = ii_bvec_copy_to_user_atomic, .ii_copy_to_user = ii_bvec_copy_to_user, @@ -234,6 +239,7 @@ struct iov_iter_ops ii_bvec_ops = { .ii_advance = ii_bvec_advance, .ii_fault_in_readable = ii_bvec_fault_in_readable, .ii_single_seg_count = ii_bvec_single_seg_count, + .ii_shorten = ii_bvec_shorten, }; EXPORT_SYMBOL(ii_bvec_ops); #endif /* CONFIG_BLOCK */ @@ -384,6 +390,14 @@ static size_t ii_iovec_single_seg_count(const struct iov_iter *i) return min(i->count, iov->iov_len - i->iov_offset); } +static int ii_iovec_shorten(struct iov_iter *i, size_t count) +{ + struct iovec *iov = (struct iovec *)i->data; + i->nr_segs = iov_shorten(iov, i->nr_segs, count); + i->count = min(i->count, count); + return 0; +} + struct iov_iter_ops ii_iovec_ops = { .ii_copy_to_user_atomic = ii_iovec_copy_to_user_atomic, .ii_copy_to_user = ii_iovec_copy_to_user, @@ -392,5 +406,6 @@ struct iov_iter_ops ii_iovec_ops = { .ii_advance = ii_iovec_advance, .ii_fault_in_readable = ii_iovec_fault_in_readable, .ii_single_seg_count = ii_iovec_single_seg_count, + .ii_shorten = ii_iovec_shorten, }; EXPORT_SYMBOL(ii_iovec_ops); diff --git a/include/linux/fs.h b/include/linux/fs.h index c2cd17ce27a3..a89bcb9573a6 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -309,6 +309,7 @@ struct iov_iter_ops { void (*ii_advance)(struct iov_iter *, size_t); int (*ii_fault_in_readable)(struct iov_iter *, size_t); size_t (*ii_single_seg_count)(const struct iov_iter *); + int (*ii_shorten)(struct iov_iter *, size_t); }; static inline size_t iov_iter_copy_to_user_atomic(struct page *page, @@ -348,6 +349,10 @@ static inline size_t iov_iter_single_seg_count(const struct iov_iter *i) { return i->ops->ii_single_seg_count(i); } +static inline int iov_iter_shorten(struct iov_iter *i, size_t count) +{ + return i->ops->ii_shorten(i, count); +} #ifdef CONFIG_BLOCK extern struct iov_iter_ops ii_bvec_ops; -- 2.39.5