new helper: iov_iter_npages()

counts the pages covered by iov_iter, up to given limit.
do_block_direct_io() and fuse_iter_npages() switched to
it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/direct-io.c b/fs/direct-io.c
index 4b410d58faae96380fa18edc75b16e64331a977a..98040ba388ac1e2db62f96f253bc141758013b10 100644 (file)
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -1100,7 +1100,6 @@ do_blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
        get_block_t get_block, dio_iodone_t end_io,
        dio_submit_t submit_io, int flags)
 {
-       int seg;
        unsigned i_blkbits = ACCESS_ONCE(inode->i_blkbits);
        unsigned blkbits = i_blkbits;
        unsigned blocksize_mask = (1 << blkbits) - 1;
@@ -1108,7 +1107,6 @@ do_blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
        loff_t end = offset + iov_iter_count(iter);
        struct dio *dio;
        struct dio_submit sdio = { 0, };
-       unsigned long user_addr;
        struct buffer_head map_bh = { 0, };
        struct blk_plug plug;
        unsigned long align = offset | iov_iter_alignment(iter);
@@ -1231,12 +1229,7 @@ do_blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
        if (unlikely(sdio.blkfactor))
                sdio.pages_in_io = 2;
 
-       for (seg = 0; seg < iter->nr_segs; seg++) {
-               user_addr = (unsigned long)iter->iov[seg].iov_base;
-               sdio.pages_in_io +=
-                       ((user_addr + iter->iov[seg].iov_len + PAGE_SIZE-1) /
-                               PAGE_SIZE - user_addr / PAGE_SIZE);
-       }
+       sdio.pages_in_io += iov_iter_npages(iter, INT_MAX);
 
        blk_start_plug(&plug);
 

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 7db564d18dc6cd9d69aa02643a5fd5af8b836991..7026014717bcd37069921b928f4877568d63d3bf 100644 (file)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1310,7 +1310,7 @@ static int fuse_get_user_pages(struct fuse_req *req, struct iov_iter *ii,
 
        while (nbytes < *nbytesp && req->num_pages < req->max_pages) {
                unsigned npages;
-               size_t start, end, frag_size;
+               size_t start;
                unsigned n = req->max_pages - req->num_pages;
                ssize_t ret = iov_iter_get_pages(ii,
                                        &req->pages[req->num_pages],
@@ -1344,19 +1344,7 @@ static int fuse_get_user_pages(struct fuse_req *req, struct iov_iter *ii,
 
 static inline int fuse_iter_npages(const struct iov_iter *ii_p)
 {
-       struct iov_iter ii = *ii_p;
-       int npages = 0;
-
-       while (iov_iter_count(&ii) && npages < FUSE_MAX_PAGES_PER_REQ) {
-               unsigned long user_addr = fuse_get_user_addr(&ii);
-               unsigned offset = user_addr & ~PAGE_MASK;
-               size_t frag_size = iov_iter_single_seg_count(&ii);
-
-               npages += (frag_size + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
-               iov_iter_advance(&ii, frag_size);
-       }
-
-       return min(npages, FUSE_MAX_PAGES_PER_REQ);
+       return iov_iter_npages(ii_p, FUSE_MAX_PAGES_PER_REQ);
 }
 
 ssize_t fuse_direct_io(struct fuse_io_priv *io, struct iov_iter *iter,

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 341986116d83dd284b84b4b8a418a7c0fc2bc82e..2f8825b066808d2741c03947c5db17eb3f9d4e09 100644 (file)
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -73,6 +73,7 @@ void iov_iter_init(struct iov_iter *i, int direction, const struct iovec *iov,
                        unsigned long nr_segs, size_t count);
 ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages,
                        size_t maxsize, size_t *start);
+int iov_iter_npages(const struct iov_iter *i, int maxpages);
 
 static inline size_t iov_iter_count(struct iov_iter *i)
 {

diff --git a/mm/iov_iter.c b/mm/iov_iter.c
index 45204cd5ccd8a9d5409e337f6a04edc3b722f954..0b677f8f9bad8576ad154c2707677fa32cd980d7 100644 (file)
--- a/mm/iov_iter.c
+++ b/mm/iov_iter.c
@@ -262,3 +262,30 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
        return (res == n ? len : res * PAGE_SIZE) - *start;
 }
 EXPORT_SYMBOL(iov_iter_get_pages);
+
+int iov_iter_npages(const struct iov_iter *i, int maxpages)
+{
+       size_t offset = i->iov_offset;
+       size_t size = i->count;
+       const struct iovec *iov = i->iov;
+       int npages = 0;
+       int n;
+
+       for (n = 0; size && n < i->nr_segs; n++, iov++) {
+               unsigned long addr = (unsigned long)iov->iov_base + offset;
+               size_t len = iov->iov_len - offset;
+               offset = 0;
+               if (unlikely(!len))     /* empty segment */
+                       continue;
+               if (len > size)
+                       len = size;
+               npages += (addr + len + PAGE_SIZE - 1) / PAGE_SIZE
+                         - addr / PAGE_SIZE;
+               if (npages >= maxpages) /* don't bother going further */
+                       return maxpages;
+               size -= len;
+               offset = 0;
+       }
+       return min(npages, maxpages);
+}
+EXPORT_SYMBOL(iov_iter_npages);