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direct-io: separate map_bh from dio
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Only a single b_private field in the map_bh buffer head is needed after
the submission path. Move map_bh separately to avoid storing
this information in the long term slab.

This avoids the weird 104 byte hole in struct dio_submit which also needed
to be memseted early.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
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Andi Kleen authored and root committed Oct 28, 2011
1 parent 6e8267f commit 1877264
Showing 1 changed file with 37 additions and 29 deletions.
66 changes: 37 additions & 29 deletions fs/direct-io.c
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Original file line number Diff line number Diff line change
Expand Up @@ -119,6 +119,7 @@ struct dio {
loff_t i_size; /* i_size when submitted */
dio_iodone_t *end_io; /* IO completion function */

void *private; /* copy from map_bh.b_private */

/* BIO completion state */
spinlock_t bio_lock; /* protects BIO fields below */
Expand All @@ -133,7 +134,6 @@ struct dio {
struct kiocb *iocb; /* kiocb */
ssize_t result; /* IO result */

struct buffer_head map_bh; /* last get_block() result */
/*
* pages[] (and any fields placed after it) are not zeroed out at
* allocation time. Don't add new fields after pages[] unless you
Expand Down Expand Up @@ -301,7 +301,7 @@ static ssize_t dio_complete(struct dio *dio, loff_t offset, ssize_t ret, bool is

if (dio->end_io && dio->result) {
dio->end_io(dio->iocb, offset, transferred,
dio->map_bh.b_private, ret, is_async);
dio->private, ret, is_async);
} else {
if (is_async)
aio_complete(dio->iocb, ret, 0);
Expand Down Expand Up @@ -574,10 +574,10 @@ static int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)
* buffer_mapped(). However the direct-io code will only process holes one
* block at a time - it will repeatedly call get_block() as it walks the hole.
*/
static int get_more_blocks(struct dio *dio, struct dio_submit *sdio)
static int get_more_blocks(struct dio *dio, struct dio_submit *sdio,
struct buffer_head *map_bh)
{
int ret;
struct buffer_head *map_bh = &dio->map_bh;
sector_t fs_startblk; /* Into file, in filesystem-sized blocks */
unsigned long fs_count; /* Number of filesystem-sized blocks */
unsigned long dio_count;/* Number of dio_block-sized blocks */
Expand Down Expand Up @@ -621,6 +621,9 @@ static int get_more_blocks(struct dio *dio, struct dio_submit *sdio)

ret = (*sdio->get_block)(dio->inode, fs_startblk,
map_bh, create);

/* Store for completion */
dio->private = map_bh->b_private;
}
return ret;
}
Expand All @@ -629,7 +632,7 @@ static int get_more_blocks(struct dio *dio, struct dio_submit *sdio)
* There is no bio. Make one now.
*/
static int dio_new_bio(struct dio *dio, struct dio_submit *sdio,
sector_t start_sector)
sector_t start_sector, struct buffer_head *map_bh)
{
sector_t sector;
int ret, nr_pages;
Expand All @@ -638,10 +641,10 @@ static int dio_new_bio(struct dio *dio, struct dio_submit *sdio,
if (ret)
goto out;
sector = start_sector << (sdio->blkbits - 9);
nr_pages = min(sdio->pages_in_io, bio_get_nr_vecs(dio->map_bh.b_bdev));
nr_pages = min(sdio->pages_in_io, bio_get_nr_vecs(map_bh->b_bdev));
nr_pages = min(nr_pages, BIO_MAX_PAGES);
BUG_ON(nr_pages <= 0);
dio_bio_alloc(dio, sdio, dio->map_bh.b_bdev, sector, nr_pages);
dio_bio_alloc(dio, sdio, map_bh->b_bdev, sector, nr_pages);
sdio->boundary = 0;
out:
return ret;
Expand Down Expand Up @@ -686,7 +689,8 @@ static int dio_bio_add_page(struct dio_submit *sdio)
* The caller of this function is responsible for removing cur_page from the
* dio, and for dropping the refcount which came from that presence.
*/
static int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio)
static int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio,
struct buffer_head *map_bh)
{
int ret = 0;

Expand Down Expand Up @@ -721,14 +725,14 @@ static int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio)
}

if (sdio->bio == NULL) {
ret = dio_new_bio(dio, sdio, sdio->cur_page_block);
ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
if (ret)
goto out;
}

if (dio_bio_add_page(sdio) != 0) {
dio_bio_submit(dio, sdio);
ret = dio_new_bio(dio, sdio, sdio->cur_page_block);
ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
if (ret == 0) {
ret = dio_bio_add_page(sdio);
BUG_ON(ret != 0);
Expand Down Expand Up @@ -757,7 +761,8 @@ static int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio)
*/
static int
submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page,
unsigned offset, unsigned len, sector_t blocknr)
unsigned offset, unsigned len, sector_t blocknr,
struct buffer_head *map_bh)
{
int ret = 0;

Expand All @@ -782,7 +787,7 @@ submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page,
* avoid metadata seeks.
*/
if (sdio->boundary) {
ret = dio_send_cur_page(dio, sdio);
ret = dio_send_cur_page(dio, sdio, map_bh);
page_cache_release(sdio->cur_page);
sdio->cur_page = NULL;
}
Expand All @@ -793,7 +798,7 @@ submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page,
* If there's a deferred page already there then send it.
*/
if (sdio->cur_page) {
ret = dio_send_cur_page(dio, sdio);
ret = dio_send_cur_page(dio, sdio, map_bh);
page_cache_release(sdio->cur_page);
sdio->cur_page = NULL;
if (ret)
Expand All @@ -815,16 +820,16 @@ submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page,
* file blocks. Only called for S_ISREG files - blockdevs do not set
* buffer_new
*/
static void clean_blockdev_aliases(struct dio *dio)
static void clean_blockdev_aliases(struct dio *dio, struct buffer_head *map_bh)
{
unsigned i;
unsigned nblocks;

nblocks = dio->map_bh.b_size >> dio->inode->i_blkbits;
nblocks = map_bh->b_size >> dio->inode->i_blkbits;

for (i = 0; i < nblocks; i++) {
unmap_underlying_metadata(dio->map_bh.b_bdev,
dio->map_bh.b_blocknr + i);
unmap_underlying_metadata(map_bh->b_bdev,
map_bh->b_blocknr + i);
}
}

Expand All @@ -837,15 +842,16 @@ static void clean_blockdev_aliases(struct dio *dio)
* `end' is zero if we're doing the start of the IO, 1 at the end of the
* IO.
*/
static void dio_zero_block(struct dio *dio, struct dio_submit *sdio, int end)
static void dio_zero_block(struct dio *dio, struct dio_submit *sdio, int end,
struct buffer_head *map_bh)
{
unsigned dio_blocks_per_fs_block;
unsigned this_chunk_blocks; /* In dio_blocks */
unsigned this_chunk_bytes;
struct page *page;

sdio->start_zero_done = 1;
if (!sdio->blkfactor || !buffer_new(&dio->map_bh))
if (!sdio->blkfactor || !buffer_new(map_bh))
return;

dio_blocks_per_fs_block = 1 << sdio->blkfactor;
Expand All @@ -865,7 +871,7 @@ static void dio_zero_block(struct dio *dio, struct dio_submit *sdio, int end)

page = ZERO_PAGE(0);
if (submit_page_section(dio, sdio, page, 0, this_chunk_bytes,
sdio->next_block_for_io))
sdio->next_block_for_io, map_bh))
return;

sdio->next_block_for_io += this_chunk_blocks;
Expand All @@ -887,13 +893,13 @@ static void dio_zero_block(struct dio *dio, struct dio_submit *sdio, int end)
* it should set b_size to PAGE_SIZE or more inside get_block(). This gives
* fine alignment but still allows this function to work in PAGE_SIZE units.
*/
static int do_direct_IO(struct dio *dio, struct dio_submit *sdio)
static int do_direct_IO(struct dio *dio, struct dio_submit *sdio,
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;
struct buffer_head *map_bh = &dio->map_bh;
int ret = 0;

/* The I/O can start at any block offset within the first page */
Expand All @@ -919,7 +925,7 @@ static int do_direct_IO(struct dio *dio, struct dio_submit *sdio)
unsigned long blkmask;
unsigned long dio_remainder;

ret = get_more_blocks(dio, sdio);
ret = get_more_blocks(dio, sdio, map_bh);
if (ret) {
page_cache_release(page);
goto out;
Expand All @@ -932,7 +938,7 @@ static int do_direct_IO(struct dio *dio, struct dio_submit *sdio)
sdio->next_block_for_io =
map_bh->b_blocknr << sdio->blkfactor;
if (buffer_new(map_bh))
clean_blockdev_aliases(dio);
clean_blockdev_aliases(dio, map_bh);

if (!sdio->blkfactor)
goto do_holes;
Expand Down Expand Up @@ -991,7 +997,7 @@ static int do_direct_IO(struct dio *dio, struct dio_submit *sdio)
* we must zero out the start of this block.
*/
if (unlikely(sdio->blkfactor && !sdio->start_zero_done))
dio_zero_block(dio, sdio, 0);
dio_zero_block(dio, sdio, 0, map_bh);

/*
* Work out, in this_chunk_blocks, how much disk we
Expand All @@ -1011,7 +1017,8 @@ static int do_direct_IO(struct dio *dio, struct dio_submit *sdio)
ret = submit_page_section(dio, sdio, page,
offset_in_page,
this_chunk_bytes,
sdio->next_block_for_io);
sdio->next_block_for_io,
map_bh);
if (ret) {
page_cache_release(page);
goto out;
Expand Down Expand Up @@ -1047,6 +1054,7 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
ssize_t ret = 0;
ssize_t ret2;
size_t bytes;
struct buffer_head map_bh = { 0, };

dio->inode = inode;
dio->rw = rw;
Expand Down Expand Up @@ -1101,7 +1109,7 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
sdio->total_pages += (bytes + PAGE_SIZE - 1) / PAGE_SIZE;
sdio->curr_user_address = user_addr;

ret = do_direct_IO(dio, sdio);
ret = do_direct_IO(dio, sdio, &map_bh);

dio->result += iov[seg].iov_len -
((sdio->final_block_in_request - sdio->block_in_file) <<
Expand All @@ -1124,10 +1132,10 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
* There may be some unwritten disk at the end of a part-written
* fs-block-sized block. Go zero that now.
*/
dio_zero_block(dio, sdio, 1);
dio_zero_block(dio, sdio, 1, &map_bh);

if (sdio->cur_page) {
ret2 = dio_send_cur_page(dio, sdio);
ret2 = dio_send_cur_page(dio, sdio, &map_bh);
if (ret == 0)
ret = ret2;
page_cache_release(sdio->cur_page);
Expand Down

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