new helper: iov_iter_get_pages()
iov_iter_get_pages(iter, pages, maxsize, &start) grabs references pinning
the pages of up to maxsize of (contiguous) data from iter. Returns the
amount of memory grabbed or -error. In case of success, the requested
area begins at offset start in pages[0] and runs through pages[1], etc.
Less than requested amount might be returned - either because the contiguous
area in the beginning of iterator is smaller than requested, or because
the kernel failed to pin that many pages.
direct-io.c switched to using iov_iter_get_pages()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 387d919..4b410d5 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -77,7 +77,6 @@
unsigned blocks_available; /* At block_in_file. changes */
int reap_counter; /* rate limit reaping */
sector_t final_block_in_request;/* doesn't change */
- unsigned first_block_in_page; /* doesn't change, Used only once */
int boundary; /* prev block is at a boundary */
get_block_t *get_block; /* block mapping function */
dio_submit_t *submit_io; /* IO submition function */
@@ -98,19 +97,14 @@
sector_t cur_page_block; /* Where it starts */
loff_t cur_page_fs_offset; /* Offset in file */
- /*
- * Page fetching state. These variables belong to dio_refill_pages().
- */
- int curr_page; /* changes */
- int total_pages; /* doesn't change */
- unsigned long curr_user_address;/* changes */
-
+ struct iov_iter *iter;
/*
* Page queue. These variables belong to dio_refill_pages() and
* dio_get_page().
*/
unsigned head; /* next page to process */
unsigned tail; /* last valid page + 1 */
+ size_t from, to;
};
/* dio_state communicated between submission path and end_io */
@@ -163,15 +157,10 @@
*/
static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)
{
- int ret;
- int nr_pages;
+ ssize_t ret;
- nr_pages = min(sdio->total_pages - sdio->curr_page, DIO_PAGES);
- ret = get_user_pages_fast(
- sdio->curr_user_address, /* Where from? */
- nr_pages, /* How many pages? */
- dio->rw == READ, /* Write to memory? */
- &dio->pages[0]); /* Put results here */
+ ret = iov_iter_get_pages(sdio->iter, dio->pages, DIO_PAGES * PAGE_SIZE,
+ &sdio->from);
if (ret < 0 && sdio->blocks_available && (dio->rw & WRITE)) {
struct page *page = ZERO_PAGE(0);
@@ -186,18 +175,19 @@
dio->pages[0] = page;
sdio->head = 0;
sdio->tail = 1;
- ret = 0;
- goto out;
+ sdio->from = 0;
+ sdio->to = PAGE_SIZE;
+ return 0;
}
if (ret >= 0) {
- sdio->curr_user_address += ret * PAGE_SIZE;
- sdio->curr_page += ret;
+ iov_iter_advance(sdio->iter, ret);
+ ret += sdio->from;
sdio->head = 0;
- sdio->tail = ret;
- ret = 0;
+ sdio->tail = (ret + PAGE_SIZE - 1) / PAGE_SIZE;
+ sdio->to = ((ret - 1) & (PAGE_SIZE - 1)) + 1;
+ return 0;
}
-out:
return ret;
}
@@ -208,8 +198,9 @@
* L1 cache.
*/
static inline struct page *dio_get_page(struct dio *dio,
- struct dio_submit *sdio)
+ struct dio_submit *sdio, size_t *from, size_t *to)
{
+ int n;
if (dio_pages_present(sdio) == 0) {
int ret;
@@ -218,7 +209,10 @@
return ERR_PTR(ret);
BUG_ON(dio_pages_present(sdio) == 0);
}
- return dio->pages[sdio->head++];
+ n = sdio->head++;
+ *from = n ? 0 : sdio->from;
+ *to = (n == sdio->tail - 1) ? sdio->to : PAGE_SIZE;
+ return dio->pages[n];
}
/**
@@ -422,8 +416,8 @@
*/
static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio)
{
- while (dio_pages_present(sdio))
- page_cache_release(dio_get_page(dio, sdio));
+ while (sdio->head < sdio->tail)
+ page_cache_release(dio->pages[sdio->head++]);
}
/*
@@ -912,23 +906,18 @@
struct buffer_head *map_bh)
{
const unsigned blkbits = sdio->blkbits;
- const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
- struct page *page;
- unsigned block_in_page;
int ret = 0;
- /* The I/O can start at any block offset within the first page */
- block_in_page = sdio->first_block_in_page;
-
while (sdio->block_in_file < sdio->final_block_in_request) {
- page = dio_get_page(dio, sdio);
+ struct page *page;
+ size_t from, to;
+ page = dio_get_page(dio, sdio, &from, &to);
if (IS_ERR(page)) {
ret = PTR_ERR(page);
goto out;
}
- while (block_in_page < blocks_per_page) {
- unsigned offset_in_page = block_in_page << blkbits;
+ while (from < to) {
unsigned this_chunk_bytes; /* # of bytes mapped */
unsigned this_chunk_blocks; /* # of blocks */
unsigned u;
@@ -999,10 +988,9 @@
page_cache_release(page);
goto out;
}
- zero_user(page, block_in_page << blkbits,
- 1 << blkbits);
+ zero_user(page, from, 1 << blkbits);
sdio->block_in_file++;
- block_in_page++;
+ from += 1 << blkbits;
dio->result += 1 << blkbits;
goto next_block;
}
@@ -1020,7 +1008,7 @@
* can add to this page
*/
this_chunk_blocks = sdio->blocks_available;
- u = (PAGE_SIZE - offset_in_page) >> blkbits;
+ u = (to - from) >> blkbits;
if (this_chunk_blocks > u)
this_chunk_blocks = u;
u = sdio->final_block_in_request - sdio->block_in_file;
@@ -1032,7 +1020,7 @@
if (this_chunk_blocks == sdio->blocks_available)
sdio->boundary = buffer_boundary(map_bh);
ret = submit_page_section(dio, sdio, page,
- offset_in_page,
+ from,
this_chunk_bytes,
sdio->next_block_for_io,
map_bh);
@@ -1043,9 +1031,9 @@
sdio->next_block_for_io += this_chunk_blocks;
sdio->block_in_file += this_chunk_blocks;
- block_in_page += this_chunk_blocks;
+ from += this_chunk_bytes;
+ dio->result += this_chunk_bytes;
sdio->blocks_available -= this_chunk_blocks;
- dio->result += this_chunk_blocks << blkbits;
next_block:
BUG_ON(sdio->block_in_file > sdio->final_block_in_request);
if (sdio->block_in_file == sdio->final_block_in_request)
@@ -1054,7 +1042,6 @@
/* Drop the ref which was taken in get_user_pages() */
page_cache_release(page);
- block_in_page = 0;
}
out:
return ret;
@@ -1122,7 +1109,6 @@
struct dio *dio;
struct dio_submit sdio = { 0, };
unsigned long user_addr;
- size_t bytes;
struct buffer_head map_bh = { 0, };
struct blk_plug plug;
unsigned long align = offset | iov_iter_alignment(iter);
@@ -1234,6 +1220,10 @@
spin_lock_init(&dio->bio_lock);
dio->refcount = 1;
+ sdio.iter = iter;
+ sdio.final_block_in_request =
+ (offset + iov_iter_count(iter)) >> blkbits;
+
/*
* In case of non-aligned buffers, we may need 2 more
* pages since we need to zero out first and last block.
@@ -1250,34 +1240,9 @@
blk_start_plug(&plug);
- for (seg = 0; seg < iter->nr_segs; seg++) {
- user_addr = (unsigned long)iter->iov[seg].iov_base;
- sdio.size += bytes = iter->iov[seg].iov_len;
-
- /* Index into the first page of the first block */
- sdio.first_block_in_page = (user_addr & ~PAGE_MASK) >> blkbits;
- sdio.final_block_in_request = sdio.block_in_file +
- (bytes >> blkbits);
- /* Page fetching state */
- sdio.head = 0;
- sdio.tail = 0;
- sdio.curr_page = 0;
-
- sdio.total_pages = 0;
- if (user_addr & (PAGE_SIZE-1)) {
- sdio.total_pages++;
- bytes -= PAGE_SIZE - (user_addr & (PAGE_SIZE - 1));
- }
- sdio.total_pages += (bytes + PAGE_SIZE - 1) / PAGE_SIZE;
- sdio.curr_user_address = user_addr;
-
- retval = do_direct_IO(dio, &sdio, &map_bh);
-
- if (retval) {
- dio_cleanup(dio, &sdio);
- break;
- }
- } /* end iovec loop */
+ retval = do_direct_IO(dio, &sdio, &map_bh);
+ if (retval)
+ dio_cleanup(dio, &sdio);
if (retval == -ENOTBLK) {
/*