*
* O_DIRECT
*
- * 04Jul2002 akpm@zip.com.au
+ * 04Jul2002 Andrew Morton
* Initial version
* 11Sep2002 janetinc@us.ibm.com
* added readv/writev support.
- * 29Oct2002 akpm@zip.com.au
+ * 29Oct2002 Andrew Morton
* rewrote bio_add_page() support.
* 30Oct2002 pbadari@us.ibm.com
* added support for non-aligned IO.
#include <linux/buffer_head.h>
#include <linux/rwsem.h>
#include <linux/uio.h>
-#include <asm/atomic.h>
+#include <linux/atomic.h>
+#include <linux/prefetch.h>
/*
* How many user pages to map in one call to get_user_pages(). This determines
- * the size of a structure on the stack.
+ * the size of a structure in the slab cache
*/
#define DIO_PAGES 64
*
* If blkfactor is zero then the user's request was aligned to the filesystem's
* blocksize.
- *
- * lock_type is DIO_LOCKING for regular files on direct-IO-naive filesystems.
- * This determines whether we need to do the fancy locking which prevents
- * direct-IO from being able to read uninitialised disk blocks. If its zero
- * (blockdev) this locking is not done, and if it is DIO_OWN_LOCKING i_mutex is
- * not held for the entire direct write (taken briefly, initially, during a
- * direct read though, but its never held for the duration of a direct-IO).
*/
-struct dio {
- /* BIO submission state */
+/* dio_state only used in the submission path */
+
+struct dio_submit {
struct bio *bio; /* bio under assembly */
- struct inode *inode;
- int rw;
- loff_t i_size; /* i_size when submitted */
- int lock_type; /* doesn't change */
unsigned blkbits; /* doesn't change */
unsigned blkfactor; /* When we're using an alignment which
is finer than the filesystem's soft
sector_t block_in_file; /* Current offset into the underlying
file in dio_block units. */
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 */
- int reap_counter; /* rate limit reaping */
get_block_t *get_block; /* block mapping function */
- dio_iodone_t *end_io; /* IO completion function */
+ dio_submit_t *submit_io; /* IO submition function */
+
+ loff_t logical_offset_in_bio; /* current first logical block in bio */
sector_t final_block_in_bio; /* current final block in bio + 1 */
sector_t next_block_for_io; /* next block to be put under IO,
in dio_blocks units */
- struct buffer_head map_bh; /* last get_block() result */
/*
* Deferred addition of a page to the dio. These variables are
unsigned cur_page_offset; /* Offset into it, in bytes */
unsigned cur_page_len; /* Nr of bytes at cur_page_offset */
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().
* Page queue. These variables belong to dio_refill_pages() and
* dio_get_page().
*/
- struct page *pages[DIO_PAGES]; /* page buffer */
unsigned head; /* next page to process */
unsigned tail; /* last valid page + 1 */
- int page_errors; /* errno from get_user_pages() */
+};
+
+/* dio_state communicated between submission path and end_io */
+struct dio {
+ int flags; /* doesn't change */
+ int rw;
+ struct inode *inode;
+ 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 */
+ int page_errors; /* errno from get_user_pages() */
+ int is_async; /* is IO async ? */
+ int io_error; /* IO error in completion path */
unsigned long refcount; /* direct_io_worker() and bios */
struct bio *bio_list; /* singly linked via bi_private */
struct task_struct *waiter; /* waiting task (NULL if none) */
/* AIO related stuff */
struct kiocb *iocb; /* kiocb */
- int is_async; /* is IO async ? */
- int io_error; /* IO error in completion path */
ssize_t result; /* IO result */
-};
+
+ /*
+ * pages[] (and any fields placed after it) are not zeroed out at
+ * allocation time. Don't add new fields after pages[] unless you
+ * wish that they not be zeroed.
+ */
+ struct page *pages[DIO_PAGES]; /* page buffer */
+} ____cacheline_aligned_in_smp;
+
+static struct kmem_cache *dio_cache __read_mostly;
+
+static void __inode_dio_wait(struct inode *inode)
+{
+ wait_queue_head_t *wq = bit_waitqueue(&inode->i_state, __I_DIO_WAKEUP);
+ DEFINE_WAIT_BIT(q, &inode->i_state, __I_DIO_WAKEUP);
+
+ do {
+ prepare_to_wait(wq, &q.wait, TASK_UNINTERRUPTIBLE);
+ if (atomic_read(&inode->i_dio_count))
+ schedule();
+ } while (atomic_read(&inode->i_dio_count));
+ finish_wait(wq, &q.wait);
+}
+
+/**
+ * inode_dio_wait - wait for outstanding DIO requests to finish
+ * @inode: inode to wait for
+ *
+ * Waits for all pending direct I/O requests to finish so that we can
+ * proceed with a truncate or equivalent operation.
+ *
+ * Must be called under a lock that serializes taking new references
+ * to i_dio_count, usually by inode->i_mutex.
+ */
+void inode_dio_wait(struct inode *inode)
+{
+ if (atomic_read(&inode->i_dio_count))
+ __inode_dio_wait(inode);
+}
+EXPORT_SYMBOL(inode_dio_wait);
+
+/*
+ * inode_dio_done - signal finish of a direct I/O requests
+ * @inode: inode the direct I/O happens on
+ *
+ * This is called once we've finished processing a direct I/O request,
+ * and is used to wake up callers waiting for direct I/O to be quiesced.
+ */
+void inode_dio_done(struct inode *inode)
+{
+ if (atomic_dec_and_test(&inode->i_dio_count))
+ wake_up_bit(&inode->i_state, __I_DIO_WAKEUP);
+}
+EXPORT_SYMBOL(inode_dio_done);
/*
* How many pages are in the queue?
*/
-static inline unsigned dio_pages_present(struct dio *dio)
+static inline unsigned dio_pages_present(struct dio_submit *sdio)
{
- return dio->tail - dio->head;
+ return sdio->tail - sdio->head;
}
/*
* Go grab and pin some userspace pages. Typically we'll get 64 at a time.
*/
-static int dio_refill_pages(struct dio *dio)
+static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)
{
int ret;
int nr_pages;
- nr_pages = min(dio->total_pages - dio->curr_page, DIO_PAGES);
- down_read(¤t->mm->mmap_sem);
- ret = get_user_pages(
- current, /* Task for fault acounting */
- current->mm, /* whose pages? */
- dio->curr_user_address, /* Where from? */
+ 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? */
- 0, /* force (?) */
- &dio->pages[0],
- NULL); /* vmas */
- up_read(¤t->mm->mmap_sem);
+ &dio->pages[0]); /* Put results here */
- if (ret < 0 && dio->blocks_available && (dio->rw & WRITE)) {
+ if (ret < 0 && sdio->blocks_available && (dio->rw & WRITE)) {
struct page *page = ZERO_PAGE(0);
/*
* A memory fault, but the filesystem has some outstanding
dio->page_errors = ret;
page_cache_get(page);
dio->pages[0] = page;
- dio->head = 0;
- dio->tail = 1;
+ sdio->head = 0;
+ sdio->tail = 1;
ret = 0;
goto out;
}
if (ret >= 0) {
- dio->curr_user_address += ret * PAGE_SIZE;
- dio->curr_page += ret;
- dio->head = 0;
- dio->tail = ret;
+ sdio->curr_user_address += ret * PAGE_SIZE;
+ sdio->curr_page += ret;
+ sdio->head = 0;
+ sdio->tail = ret;
ret = 0;
}
out:
* decent number of pages, less frequently. To provide nicer use of the
* L1 cache.
*/
-static struct page *dio_get_page(struct dio *dio)
+static inline struct page *dio_get_page(struct dio *dio,
+ struct dio_submit *sdio)
{
- if (dio_pages_present(dio) == 0) {
+ if (dio_pages_present(sdio) == 0) {
int ret;
- ret = dio_refill_pages(dio);
+ ret = dio_refill_pages(dio, sdio);
if (ret)
return ERR_PTR(ret);
- BUG_ON(dio_pages_present(dio) == 0);
+ BUG_ON(dio_pages_present(sdio) == 0);
}
- return dio->pages[dio->head++];
+ return dio->pages[sdio->head++];
}
/**
* filesystems can use it to hold additional state between get_block calls and
* dio_complete.
*/
-static int dio_complete(struct dio *dio, loff_t offset, int ret)
+static ssize_t dio_complete(struct dio *dio, loff_t offset, ssize_t ret, bool is_async)
{
ssize_t transferred = 0;
transferred = dio->i_size - offset;
}
- if (dio->end_io && dio->result)
- dio->end_io(dio->iocb, offset, transferred,
- dio->map_bh.b_private);
- if (dio->lock_type == DIO_LOCKING)
- /* lockdep: non-owner release */
- up_read_non_owner(&dio->inode->i_alloc_sem);
-
if (ret == 0)
ret = dio->page_errors;
if (ret == 0)
if (ret == 0)
ret = transferred;
+ if (dio->end_io && dio->result) {
+ dio->end_io(dio->iocb, offset, transferred,
+ dio->private, ret, is_async);
+ } else {
+ if (is_async)
+ aio_complete(dio->iocb, ret, 0);
+ inode_dio_done(dio->inode);
+ }
+
return ret;
}
spin_unlock_irqrestore(&dio->bio_lock, flags);
if (remaining == 0) {
- int ret = dio_complete(dio, dio->iocb->ki_pos, 0);
- aio_complete(dio->iocb, ret, 0);
- kfree(dio);
+ dio_complete(dio, dio->iocb->ki_pos, 0, true);
+ kmem_cache_free(dio_cache, dio);
}
}
spin_unlock_irqrestore(&dio->bio_lock, flags);
}
-static int
-dio_bio_alloc(struct dio *dio, struct block_device *bdev,
- sector_t first_sector, int nr_vecs)
+/**
+ * dio_end_io - handle the end io action for the given bio
+ * @bio: The direct io bio thats being completed
+ * @error: Error if there was one
+ *
+ * This is meant to be called by any filesystem that uses their own dio_submit_t
+ * so that the DIO specific endio actions are dealt with after the filesystem
+ * has done it's completion work.
+ */
+void dio_end_io(struct bio *bio, int error)
+{
+ struct dio *dio = bio->bi_private;
+
+ if (dio->is_async)
+ dio_bio_end_aio(bio, error);
+ else
+ dio_bio_end_io(bio, error);
+}
+EXPORT_SYMBOL_GPL(dio_end_io);
+
+static inline void
+dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
+ struct block_device *bdev,
+ sector_t first_sector, int nr_vecs)
{
struct bio *bio;
+ /*
+ * bio_alloc() is guaranteed to return a bio when called with
+ * __GFP_WAIT and we request a valid number of vectors.
+ */
bio = bio_alloc(GFP_KERNEL, nr_vecs);
- if (bio == NULL)
- return -ENOMEM;
bio->bi_bdev = bdev;
bio->bi_sector = first_sector;
else
bio->bi_end_io = dio_bio_end_io;
- dio->bio = bio;
- return 0;
+ sdio->bio = bio;
+ sdio->logical_offset_in_bio = sdio->cur_page_fs_offset;
}
/*
*
* bios hold a dio reference between submit_bio and ->end_io.
*/
-static void dio_bio_submit(struct dio *dio)
+static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
{
- struct bio *bio = dio->bio;
+ struct bio *bio = sdio->bio;
unsigned long flags;
bio->bi_private = dio;
if (dio->is_async && dio->rw == READ)
bio_set_pages_dirty(bio);
- submit_bio(dio->rw, bio);
+ if (sdio->submit_io)
+ sdio->submit_io(dio->rw, bio, dio->inode,
+ sdio->logical_offset_in_bio);
+ else
+ submit_bio(dio->rw, bio);
- dio->bio = NULL;
- dio->boundary = 0;
+ sdio->bio = NULL;
+ sdio->boundary = 0;
+ sdio->logical_offset_in_bio = 0;
}
/*
* Release any resources in case of a failure
*/
-static void dio_cleanup(struct dio *dio)
+static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio)
{
- while (dio_pages_present(dio))
- page_cache_release(dio_get_page(dio));
+ while (dio_pages_present(sdio))
+ page_cache_release(dio_get_page(dio, sdio));
}
/*
*
* This also helps to limit the peak amount of pinned userspace memory.
*/
-static int dio_bio_reap(struct dio *dio)
+static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)
{
int ret = 0;
- if (dio->reap_counter++ >= 64) {
+ if (sdio->reap_counter++ >= 64) {
while (dio->bio_list) {
unsigned long flags;
struct bio *bio;
if (ret == 0)
ret = ret2;
}
- dio->reap_counter = 0;
+ sdio->reap_counter = 0;
}
return ret;
}
/*
* Call into the fs to map some more disk blocks. We record the current number
- * of available blocks at dio->blocks_available. These are in units of the
+ * of available blocks at sdio->blocks_available. These are in units of the
* fs blocksize, (1 << inode->i_blkbits).
*
* The fs is allowed to map lots of blocks at once. If it wants to do that,
* 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)
+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 */
+ sector_t fs_endblk; /* 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 */
- unsigned long blkmask;
int create;
/*
*/
ret = dio->page_errors;
if (ret == 0) {
- BUG_ON(dio->block_in_file >= dio->final_block_in_request);
- fs_startblk = dio->block_in_file >> dio->blkfactor;
- dio_count = dio->final_block_in_request - dio->block_in_file;
- fs_count = dio_count >> dio->blkfactor;
- blkmask = (1 << dio->blkfactor) - 1;
- if (dio_count & blkmask)
- fs_count++;
+ BUG_ON(sdio->block_in_file >= sdio->final_block_in_request);
+ fs_startblk = sdio->block_in_file >> sdio->blkfactor;
+ fs_endblk = (sdio->final_block_in_request - 1) >>
+ sdio->blkfactor;
+ fs_count = fs_endblk - fs_startblk + 1;
map_bh->b_state = 0;
map_bh->b_size = fs_count << dio->inode->i_blkbits;
+ /*
+ * For writes inside i_size on a DIO_SKIP_HOLES filesystem we
+ * forbid block creations: only overwrites are permitted.
+ * We will return early to the caller once we see an
+ * unmapped buffer head returned, and the caller will fall
+ * back to buffered I/O.
+ *
+ * Otherwise the decision is left to the get_blocks method,
+ * which may decide to handle it or also return an unmapped
+ * buffer head.
+ */
create = dio->rw & WRITE;
- if (dio->lock_type == DIO_LOCKING) {
- if (dio->block_in_file < (i_size_read(dio->inode) >>
- dio->blkbits))
+ if (dio->flags & DIO_SKIP_HOLES) {
+ if (sdio->block_in_file < (i_size_read(dio->inode) >>
+ sdio->blkbits))
create = 0;
- } else if (dio->lock_type == DIO_NO_LOCKING) {
- create = 0;
}
- /*
- * For writes inside i_size we forbid block creations: only
- * overwrites are permitted. We fall back to buffered writes
- * at a higher level for inside-i_size block-instantiating
- * writes.
- */
- ret = (*dio->get_block)(dio->inode, fs_startblk,
+ ret = (*sdio->get_block)(dio->inode, fs_startblk,
map_bh, create);
+
+ /* Store for completion */
+ dio->private = map_bh->b_private;
}
return ret;
}
/*
* There is no bio. Make one now.
*/
-static int dio_new_bio(struct dio *dio, sector_t start_sector)
+static inline int dio_new_bio(struct dio *dio, struct dio_submit *sdio,
+ sector_t start_sector, struct buffer_head *map_bh)
{
sector_t sector;
int ret, nr_pages;
- ret = dio_bio_reap(dio);
+ ret = dio_bio_reap(dio, sdio);
if (ret)
goto out;
- sector = start_sector << (dio->blkbits - 9);
- nr_pages = min(dio->pages_in_io, bio_get_nr_vecs(dio->map_bh.b_bdev));
+ sector = start_sector << (sdio->blkbits - 9);
+ 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);
- ret = dio_bio_alloc(dio, dio->map_bh.b_bdev, sector, nr_pages);
- dio->boundary = 0;
+ dio_bio_alloc(dio, sdio, map_bh->b_bdev, sector, nr_pages);
+ sdio->boundary = 0;
out:
return ret;
}
*
* Return zero on success. Non-zero means the caller needs to start a new BIO.
*/
-static int dio_bio_add_page(struct dio *dio)
+static inline int dio_bio_add_page(struct dio_submit *sdio)
{
int ret;
- ret = bio_add_page(dio->bio, dio->cur_page,
- dio->cur_page_len, dio->cur_page_offset);
- if (ret == dio->cur_page_len) {
+ ret = bio_add_page(sdio->bio, sdio->cur_page,
+ sdio->cur_page_len, sdio->cur_page_offset);
+ if (ret == sdio->cur_page_len) {
/*
* Decrement count only, if we are done with this page
*/
- if ((dio->cur_page_len + dio->cur_page_offset) == PAGE_SIZE)
- dio->pages_in_io--;
- page_cache_get(dio->cur_page);
- dio->final_block_in_bio = dio->cur_page_block +
- (dio->cur_page_len >> dio->blkbits);
+ if ((sdio->cur_page_len + sdio->cur_page_offset) == PAGE_SIZE)
+ sdio->pages_in_io--;
+ page_cache_get(sdio->cur_page);
+ sdio->final_block_in_bio = sdio->cur_page_block +
+ (sdio->cur_page_len >> sdio->blkbits);
ret = 0;
} else {
ret = 1;
* 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)
+static inline int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio,
+ struct buffer_head *map_bh)
{
int ret = 0;
- if (dio->bio) {
+ if (sdio->bio) {
+ loff_t cur_offset = sdio->cur_page_fs_offset;
+ loff_t bio_next_offset = sdio->logical_offset_in_bio +
+ sdio->bio->bi_size;
+
/*
- * See whether this new request is contiguous with the old
+ * See whether this new request is contiguous with the old.
+ *
+ * Btrfs cannot handle having logically non-contiguous requests
+ * submitted. For example if you have
+ *
+ * Logical: [0-4095][HOLE][8192-12287]
+ * Physical: [0-4095] [4096-8191]
+ *
+ * We cannot submit those pages together as one BIO. So if our
+ * current logical offset in the file does not equal what would
+ * be the next logical offset in the bio, submit the bio we
+ * have.
*/
- if (dio->final_block_in_bio != dio->cur_page_block)
- dio_bio_submit(dio);
+ if (sdio->final_block_in_bio != sdio->cur_page_block ||
+ cur_offset != bio_next_offset)
+ dio_bio_submit(dio, sdio);
/*
* Submit now if the underlying fs is about to perform a
* metadata read
*/
- if (dio->boundary)
- dio_bio_submit(dio);
+ else if (sdio->boundary)
+ dio_bio_submit(dio, sdio);
}
- if (dio->bio == NULL) {
- ret = dio_new_bio(dio, dio->cur_page_block);
+ if (sdio->bio == NULL) {
+ ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
if (ret)
goto out;
}
- if (dio_bio_add_page(dio) != 0) {
- dio_bio_submit(dio);
- ret = dio_new_bio(dio, dio->cur_page_block);
+ if (dio_bio_add_page(sdio) != 0) {
+ dio_bio_submit(dio, sdio);
+ ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
if (ret == 0) {
- ret = dio_bio_add_page(dio);
+ ret = dio_bio_add_page(sdio);
BUG_ON(ret != 0);
}
}
* If that doesn't work out then we put the old page into the bio and add this
* page to the dio instead.
*/
-static int
-submit_page_section(struct dio *dio, struct page *page,
- unsigned offset, unsigned len, sector_t blocknr)
+static inline int
+submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page,
+ unsigned offset, unsigned len, sector_t blocknr,
+ struct buffer_head *map_bh)
{
int ret = 0;
/*
* Can we just grow the current page's presence in the dio?
*/
- if ( (dio->cur_page == page) &&
- (dio->cur_page_offset + dio->cur_page_len == offset) &&
- (dio->cur_page_block +
- (dio->cur_page_len >> dio->blkbits) == blocknr)) {
- dio->cur_page_len += len;
+ if (sdio->cur_page == page &&
+ sdio->cur_page_offset + sdio->cur_page_len == offset &&
+ sdio->cur_page_block +
+ (sdio->cur_page_len >> sdio->blkbits) == blocknr) {
+ sdio->cur_page_len += len;
/*
- * If dio->boundary then we want to schedule the IO now to
+ * If sdio->boundary then we want to schedule the IO now to
* avoid metadata seeks.
*/
- if (dio->boundary) {
- ret = dio_send_cur_page(dio);
- page_cache_release(dio->cur_page);
- dio->cur_page = NULL;
+ if (sdio->boundary) {
+ ret = dio_send_cur_page(dio, sdio, map_bh);
+ page_cache_release(sdio->cur_page);
+ sdio->cur_page = NULL;
}
goto out;
}
/*
* If there's a deferred page already there then send it.
*/
- if (dio->cur_page) {
- ret = dio_send_cur_page(dio);
- page_cache_release(dio->cur_page);
- dio->cur_page = NULL;
+ if (sdio->cur_page) {
+ ret = dio_send_cur_page(dio, sdio, map_bh);
+ page_cache_release(sdio->cur_page);
+ sdio->cur_page = NULL;
if (ret)
goto out;
}
page_cache_get(page); /* It is in dio */
- dio->cur_page = page;
- dio->cur_page_offset = offset;
- dio->cur_page_len = len;
- dio->cur_page_block = blocknr;
+ sdio->cur_page = page;
+ sdio->cur_page_offset = offset;
+ sdio->cur_page_len = len;
+ sdio->cur_page_block = blocknr;
+ sdio->cur_page_fs_offset = sdio->block_in_file << sdio->blkbits;
out:
return ret;
}
* 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);
}
}
* `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, int end)
+static inline 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;
- dio->start_zero_done = 1;
- if (!dio->blkfactor || !buffer_new(&dio->map_bh))
+ sdio->start_zero_done = 1;
+ if (!sdio->blkfactor || !buffer_new(map_bh))
return;
- dio_blocks_per_fs_block = 1 << dio->blkfactor;
- this_chunk_blocks = dio->block_in_file & (dio_blocks_per_fs_block - 1);
+ dio_blocks_per_fs_block = 1 << sdio->blkfactor;
+ this_chunk_blocks = sdio->block_in_file & (dio_blocks_per_fs_block - 1);
if (!this_chunk_blocks)
return;
if (end)
this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks;
- this_chunk_bytes = this_chunk_blocks << dio->blkbits;
+ this_chunk_bytes = this_chunk_blocks << sdio->blkbits;
page = ZERO_PAGE(0);
- if (submit_page_section(dio, page, 0, this_chunk_bytes,
- dio->next_block_for_io))
+ if (submit_page_section(dio, sdio, page, 0, this_chunk_bytes,
+ sdio->next_block_for_io, map_bh))
return;
- dio->next_block_for_io += this_chunk_blocks;
+ sdio->next_block_for_io += this_chunk_blocks;
}
/*
* 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)
+static int do_direct_IO(struct dio *dio, struct dio_submit *sdio,
+ struct buffer_head *map_bh)
{
- const unsigned blkbits = dio->blkbits;
+ 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 */
- block_in_page = dio->first_block_in_page;
+ block_in_page = sdio->first_block_in_page;
- while (dio->block_in_file < dio->final_block_in_request) {
- page = dio_get_page(dio);
+ while (sdio->block_in_file < sdio->final_block_in_request) {
+ page = dio_get_page(dio, sdio);
if (IS_ERR(page)) {
ret = PTR_ERR(page);
goto out;
unsigned this_chunk_blocks; /* # of blocks */
unsigned u;
- if (dio->blocks_available == 0) {
+ if (sdio->blocks_available == 0) {
/*
* Need to go and map some more disk
*/
unsigned long blkmask;
unsigned long dio_remainder;
- ret = get_more_blocks(dio);
+ ret = get_more_blocks(dio, sdio, map_bh);
if (ret) {
page_cache_release(page);
goto out;
if (!buffer_mapped(map_bh))
goto do_holes;
- dio->blocks_available =
- map_bh->b_size >> dio->blkbits;
- dio->next_block_for_io =
- map_bh->b_blocknr << dio->blkfactor;
+ sdio->blocks_available =
+ map_bh->b_size >> sdio->blkbits;
+ 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 (!dio->blkfactor)
+ if (!sdio->blkfactor)
goto do_holes;
- blkmask = (1 << dio->blkfactor) - 1;
- dio_remainder = (dio->block_in_file & blkmask);
+ blkmask = (1 << sdio->blkfactor) - 1;
+ dio_remainder = (sdio->block_in_file & blkmask);
/*
* If we are at the start of IO and that IO
* on-disk
*/
if (!buffer_new(map_bh))
- dio->next_block_for_io += dio_remainder;
- dio->blocks_available -= dio_remainder;
+ sdio->next_block_for_io += dio_remainder;
+ sdio->blocks_available -= dio_remainder;
}
do_holes:
/* Handle holes */
*/
i_size_aligned = ALIGN(i_size_read(dio->inode),
1 << blkbits);
- if (dio->block_in_file >=
+ if (sdio->block_in_file >=
i_size_aligned >> blkbits) {
/* We hit eof */
page_cache_release(page);
}
zero_user(page, block_in_page << blkbits,
1 << blkbits);
- dio->block_in_file++;
+ sdio->block_in_file++;
block_in_page++;
goto next_block;
}
* is finer than the underlying fs, go check to see if
* we must zero out the start of this block.
*/
- if (unlikely(dio->blkfactor && !dio->start_zero_done))
- dio_zero_block(dio, 0);
+ if (unlikely(sdio->blkfactor && !sdio->start_zero_done))
+ dio_zero_block(dio, sdio, 0, map_bh);
/*
* Work out, in this_chunk_blocks, how much disk we
* can add to this page
*/
- this_chunk_blocks = dio->blocks_available;
+ this_chunk_blocks = sdio->blocks_available;
u = (PAGE_SIZE - offset_in_page) >> blkbits;
if (this_chunk_blocks > u)
this_chunk_blocks = u;
- u = dio->final_block_in_request - dio->block_in_file;
+ u = sdio->final_block_in_request - sdio->block_in_file;
if (this_chunk_blocks > u)
this_chunk_blocks = u;
this_chunk_bytes = this_chunk_blocks << blkbits;
BUG_ON(this_chunk_bytes == 0);
- dio->boundary = buffer_boundary(map_bh);
- ret = submit_page_section(dio, page, offset_in_page,
- this_chunk_bytes, dio->next_block_for_io);
+ sdio->boundary = buffer_boundary(map_bh);
+ ret = submit_page_section(dio, sdio, page,
+ offset_in_page,
+ this_chunk_bytes,
+ sdio->next_block_for_io,
+ map_bh);
if (ret) {
page_cache_release(page);
goto out;
}
- dio->next_block_for_io += this_chunk_blocks;
+ sdio->next_block_for_io += this_chunk_blocks;
- dio->block_in_file += this_chunk_blocks;
+ sdio->block_in_file += this_chunk_blocks;
block_in_page += this_chunk_blocks;
- dio->blocks_available -= this_chunk_blocks;
+ sdio->blocks_available -= this_chunk_blocks;
next_block:
- BUG_ON(dio->block_in_file > dio->final_block_in_request);
- if (dio->block_in_file == dio->final_block_in_request)
+ BUG_ON(sdio->block_in_file > sdio->final_block_in_request);
+ if (sdio->block_in_file == sdio->final_block_in_request)
break;
}
return ret;
}
+static inline int drop_refcount(struct dio *dio)
+{
+ int ret2;
+ unsigned long flags;
+
+ /*
+ * Sync will always be dropping the final ref and completing the
+ * operation. AIO can if it was a broken operation described above or
+ * in fact if all the bios race to complete before we get here. In
+ * that case dio_complete() translates the EIOCBQUEUED into the proper
+ * return code that the caller will hand to aio_complete().
+ *
+ * This is managed by the bio_lock instead of being an atomic_t so that
+ * completion paths can drop their ref and use the remaining count to
+ * decide to wake the submission path atomically.
+ */
+ spin_lock_irqsave(&dio->bio_lock, flags);
+ ret2 = --dio->refcount;
+ spin_unlock_irqrestore(&dio->bio_lock, flags);
+ return ret2;
+}
+
/*
- * Releases both i_mutex and i_alloc_sem
+ * This is a library function for use by filesystem drivers.
+ *
+ * The locking rules are governed by the flags parameter:
+ * - if the flags value contains DIO_LOCKING we use a fancy locking
+ * scheme for dumb filesystems.
+ * For writes this function is called under i_mutex and returns with
+ * i_mutex held, for reads, i_mutex is not held on entry, but it is
+ * taken and dropped again before returning.
+ * - if the flags value does NOT contain DIO_LOCKING we don't use any
+ * internal locking but rather rely on the filesystem to synchronize
+ * direct I/O reads/writes versus each other and truncate.
+ *
+ * To help with locking against truncate we incremented the i_dio_count
+ * counter before starting direct I/O, and decrement it once we are done.
+ * Truncate can wait for it to reach zero to provide exclusion. It is
+ * expected that filesystem provide exclusion between new direct I/O
+ * and truncates. For DIO_LOCKING filesystems this is done by i_mutex,
+ * but other filesystems need to take care of this on their own.
+ *
+ * NOTE: if you pass "sdio" to anything by pointer make sure that function
+ * is always inlined. Otherwise gcc is unable to split the structure into
+ * individual fields and will generate much worse code. This is important
+ * for the whole file.
*/
-static ssize_t
-direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
- const struct iovec *iov, loff_t offset, unsigned long nr_segs,
- unsigned blkbits, get_block_t get_block, dio_iodone_t end_io,
- struct dio *dio)
+static inline ssize_t
+do_blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
+ struct block_device *bdev, const struct iovec *iov, loff_t offset,
+ unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io,
+ dio_submit_t submit_io, int flags)
{
- unsigned long user_addr;
- unsigned long flags;
int seg;
- ssize_t ret = 0;
- ssize_t ret2;
+ size_t size;
+ unsigned long addr;
+ unsigned blkbits = inode->i_blkbits;
+ unsigned blocksize_mask = (1 << blkbits) - 1;
+ ssize_t retval = -EINVAL;
+ loff_t end = offset;
+ struct dio *dio;
+ struct dio_submit sdio = { 0, };
+ unsigned long user_addr;
size_t bytes;
+ struct buffer_head map_bh = { 0, };
+
+ if (rw & WRITE)
+ rw = WRITE_ODIRECT;
+
+ /*
+ * Avoid references to bdev if not absolutely needed to give
+ * the early prefetch in the caller enough time.
+ */
+
+ if (offset & blocksize_mask) {
+ if (bdev)
+ blkbits = blksize_bits(bdev_logical_block_size(bdev));
+ blocksize_mask = (1 << blkbits) - 1;
+ if (offset & blocksize_mask)
+ goto out;
+ }
+
+ /* Check the memory alignment. Blocks cannot straddle pages */
+ for (seg = 0; seg < nr_segs; seg++) {
+ addr = (unsigned long)iov[seg].iov_base;
+ size = iov[seg].iov_len;
+ end += size;
+ if (unlikely((addr & blocksize_mask) ||
+ (size & blocksize_mask))) {
+ if (bdev)
+ blkbits = blksize_bits(
+ bdev_logical_block_size(bdev));
+ blocksize_mask = (1 << blkbits) - 1;
+ if ((addr & blocksize_mask) || (size & blocksize_mask))
+ goto out;
+ }
+ }
+
+ /* watch out for a 0 len io from a tricksy fs */
+ if (rw == READ && end == offset)
+ return 0;
+
+ dio = kmem_cache_alloc(dio_cache, GFP_KERNEL);
+ retval = -ENOMEM;
+ if (!dio)
+ goto out;
+ /*
+ * Believe it or not, zeroing out the page array caused a .5%
+ * performance regression in a database benchmark. So, we take
+ * care to only zero out what's needed.
+ */
+ memset(dio, 0, offsetof(struct dio, pages));
+
+ dio->flags = flags;
+ if (dio->flags & DIO_LOCKING) {
+ if (rw == READ) {
+ struct address_space *mapping =
+ iocb->ki_filp->f_mapping;
+
+ /* will be released by direct_io_worker */
+ mutex_lock(&inode->i_mutex);
+
+ retval = filemap_write_and_wait_range(mapping, offset,
+ end - 1);
+ if (retval) {
+ mutex_unlock(&inode->i_mutex);
+ kmem_cache_free(dio_cache, dio);
+ goto out;
+ }
+ }
+ }
+
+ /*
+ * Will be decremented at I/O completion time.
+ */
+ atomic_inc(&inode->i_dio_count);
+
+ /*
+ * For file extending writes updating i_size before data
+ * writeouts complete can expose uninitialized blocks. So
+ * even for AIO, we need to wait for i/o to complete before
+ * returning in this case.
+ */
+ dio->is_async = !is_sync_kiocb(iocb) && !((rw & WRITE) &&
+ (end > i_size_read(inode)));
+
+ retval = 0;
dio->inode = inode;
dio->rw = rw;
- dio->blkbits = blkbits;
- dio->blkfactor = inode->i_blkbits - blkbits;
- dio->block_in_file = offset >> blkbits;
+ sdio.blkbits = blkbits;
+ sdio.blkfactor = inode->i_blkbits - blkbits;
+ sdio.block_in_file = offset >> blkbits;
- dio->get_block = get_block;
+ sdio.get_block = get_block;
dio->end_io = end_io;
- dio->final_block_in_bio = -1;
- dio->next_block_for_io = -1;
+ sdio.submit_io = submit_io;
+ sdio.final_block_in_bio = -1;
+ sdio.next_block_for_io = -1;
dio->iocb = iocb;
dio->i_size = i_size_read(inode);
* In case of non-aligned buffers, we may need 2 more
* pages since we need to zero out first and last block.
*/
- if (unlikely(dio->blkfactor))
- dio->pages_in_io = 2;
+ if (unlikely(sdio.blkfactor))
+ sdio.pages_in_io = 2;
for (seg = 0; seg < nr_segs; seg++) {
user_addr = (unsigned long)iov[seg].iov_base;
- dio->pages_in_io +=
- ((user_addr+iov[seg].iov_len +PAGE_SIZE-1)/PAGE_SIZE
- - user_addr/PAGE_SIZE);
+ sdio.pages_in_io +=
+ ((user_addr + iov[seg].iov_len + PAGE_SIZE-1) /
+ PAGE_SIZE - user_addr / PAGE_SIZE);
}
for (seg = 0; seg < nr_segs; seg++) {
user_addr = (unsigned long)iov[seg].iov_base;
- dio->size += bytes = iov[seg].iov_len;
+ sdio.size += bytes = iov[seg].iov_len;
/* Index into the first page of the first block */
- dio->first_block_in_page = (user_addr & ~PAGE_MASK) >> blkbits;
- dio->final_block_in_request = dio->block_in_file +
+ sdio.first_block_in_page = (user_addr & ~PAGE_MASK) >> blkbits;
+ sdio.final_block_in_request = sdio.block_in_file +
(bytes >> blkbits);
/* Page fetching state */
- dio->head = 0;
- dio->tail = 0;
- dio->curr_page = 0;
+ sdio.head = 0;
+ sdio.tail = 0;
+ sdio.curr_page = 0;
- dio->total_pages = 0;
+ sdio.total_pages = 0;
if (user_addr & (PAGE_SIZE-1)) {
- dio->total_pages++;
+ sdio.total_pages++;
bytes -= PAGE_SIZE - (user_addr & (PAGE_SIZE - 1));
}
- dio->total_pages += (bytes + PAGE_SIZE - 1) / PAGE_SIZE;
- dio->curr_user_address = user_addr;
-
- ret = do_direct_IO(dio);
+ sdio.total_pages += (bytes + PAGE_SIZE - 1) / PAGE_SIZE;
+ sdio.curr_user_address = user_addr;
+
+ retval = do_direct_IO(dio, &sdio, &map_bh);
dio->result += iov[seg].iov_len -
- ((dio->final_block_in_request - dio->block_in_file) <<
+ ((sdio.final_block_in_request - sdio.block_in_file) <<
blkbits);
- if (ret) {
- dio_cleanup(dio);
+ if (retval) {
+ dio_cleanup(dio, &sdio);
break;
}
} /* end iovec loop */
- if (ret == -ENOTBLK && (rw & WRITE)) {
+ if (retval == -ENOTBLK) {
/*
* The remaining part of the request will be
* be handled by buffered I/O when we return
*/
- ret = 0;
+ retval = 0;
}
/*
* 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, 1);
-
- if (dio->cur_page) {
- ret2 = dio_send_cur_page(dio);
- if (ret == 0)
- ret = ret2;
- page_cache_release(dio->cur_page);
- dio->cur_page = NULL;
- }
- if (dio->bio)
- dio_bio_submit(dio);
+ dio_zero_block(dio, &sdio, 1, &map_bh);
- /* All IO is now issued, send it on its way */
- blk_run_address_space(inode->i_mapping);
+ if (sdio.cur_page) {
+ ssize_t ret2;
+
+ ret2 = dio_send_cur_page(dio, &sdio, &map_bh);
+ if (retval == 0)
+ retval = ret2;
+ page_cache_release(sdio.cur_page);
+ sdio.cur_page = NULL;
+ }
+ if (sdio.bio)
+ dio_bio_submit(dio, &sdio);
/*
* It is possible that, we return short IO due to end of file.
* In that case, we need to release all the pages we got hold on.
*/
- dio_cleanup(dio);
+ dio_cleanup(dio, &sdio);
/*
* All block lookups have been performed. For READ requests
* we can let i_mutex go now that its achieved its purpose
* of protecting us from looking up uninitialized blocks.
*/
- if ((rw == READ) && (dio->lock_type == DIO_LOCKING))
+ if (rw == READ && (dio->flags & DIO_LOCKING))
mutex_unlock(&dio->inode->i_mutex);
/*
* call aio_complete is when we return -EIOCBQUEUED, so we key on that.
* This had *better* be the only place that raises -EIOCBQUEUED.
*/
- BUG_ON(ret == -EIOCBQUEUED);
- if (dio->is_async && ret == 0 && dio->result &&
- ((rw & READ) || (dio->result == dio->size)))
- ret = -EIOCBQUEUED;
+ BUG_ON(retval == -EIOCBQUEUED);
+ if (dio->is_async && retval == 0 && dio->result &&
+ ((rw & READ) || (dio->result == sdio.size)))
+ retval = -EIOCBQUEUED;
- if (ret != -EIOCBQUEUED)
+ if (retval != -EIOCBQUEUED)
dio_await_completion(dio);
- /*
- * Sync will always be dropping the final ref and completing the
- * operation. AIO can if it was a broken operation described above or
- * in fact if all the bios race to complete before we get here. In
- * that case dio_complete() translates the EIOCBQUEUED into the proper
- * return code that the caller will hand to aio_complete().
- *
- * This is managed by the bio_lock instead of being an atomic_t so that
- * completion paths can drop their ref and use the remaining count to
- * decide to wake the submission path atomically.
- */
- spin_lock_irqsave(&dio->bio_lock, flags);
- ret2 = --dio->refcount;
- spin_unlock_irqrestore(&dio->bio_lock, flags);
-
- if (ret2 == 0) {
- ret = dio_complete(dio, offset, ret);
- kfree(dio);
+ if (drop_refcount(dio) == 0) {
+ retval = dio_complete(dio, offset, retval, false);
+ kmem_cache_free(dio_cache, dio);
} else
- BUG_ON(ret != -EIOCBQUEUED);
+ BUG_ON(retval != -EIOCBQUEUED);
- return ret;
+out:
+ return retval;
}
-/*
- * This is a library function for use by filesystem drivers.
- * The locking rules are governed by the dio_lock_type parameter.
- *
- * DIO_NO_LOCKING (no locking, for raw block device access)
- * For writes, i_mutex is not held on entry; it is never taken.
- *
- * DIO_LOCKING (simple locking for regular files)
- * For writes we are called under i_mutex and return with i_mutex held, even
- * though it is internally dropped.
- * For reads, i_mutex is not held on entry, but it is taken and dropped before
- * returning.
- *
- * DIO_OWN_LOCKING (filesystem provides synchronisation and handling of
- * uninitialised data, allowing parallel direct readers and writers)
- * For writes we are called without i_mutex, return without it, never touch it.
- * For reads we are called under i_mutex and return with i_mutex held, even
- * though it may be internally dropped.
- *
- * Additional i_alloc_sem locking requirements described inline below.
- */
ssize_t
__blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
- struct block_device *bdev, const struct iovec *iov, loff_t offset,
+ struct block_device *bdev, const struct iovec *iov, loff_t offset,
unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io,
- int dio_lock_type)
+ dio_submit_t submit_io, int flags)
{
- int seg;
- size_t size;
- unsigned long addr;
- unsigned blkbits = inode->i_blkbits;
- unsigned bdev_blkbits = 0;
- unsigned blocksize_mask = (1 << blkbits) - 1;
- ssize_t retval = -EINVAL;
- loff_t end = offset;
- struct dio *dio;
- int release_i_mutex = 0;
- int acquire_i_mutex = 0;
-
- if (rw & WRITE)
- rw = WRITE_SYNC;
-
- if (bdev)
- bdev_blkbits = blksize_bits(bdev_hardsect_size(bdev));
-
- if (offset & blocksize_mask) {
- if (bdev)
- blkbits = bdev_blkbits;
- blocksize_mask = (1 << blkbits) - 1;
- if (offset & blocksize_mask)
- goto out;
- }
-
- /* Check the memory alignment. Blocks cannot straddle pages */
- for (seg = 0; seg < nr_segs; seg++) {
- addr = (unsigned long)iov[seg].iov_base;
- size = iov[seg].iov_len;
- end += size;
- if ((addr & blocksize_mask) || (size & blocksize_mask)) {
- if (bdev)
- blkbits = bdev_blkbits;
- blocksize_mask = (1 << blkbits) - 1;
- if ((addr & blocksize_mask) || (size & blocksize_mask))
- goto out;
- }
- }
-
- dio = kzalloc(sizeof(*dio), GFP_KERNEL);
- retval = -ENOMEM;
- if (!dio)
- goto out;
-
- /*
- * For block device access DIO_NO_LOCKING is used,
- * neither readers nor writers do any locking at all
- * For regular files using DIO_LOCKING,
- * readers need to grab i_mutex and i_alloc_sem
- * writers need to grab i_alloc_sem only (i_mutex is already held)
- * For regular files using DIO_OWN_LOCKING,
- * neither readers nor writers take any locks here
- */
- dio->lock_type = dio_lock_type;
- if (dio_lock_type != DIO_NO_LOCKING) {
- /* watch out for a 0 len io from a tricksy fs */
- if (rw == READ && end > offset) {
- struct address_space *mapping;
-
- mapping = iocb->ki_filp->f_mapping;
- if (dio_lock_type != DIO_OWN_LOCKING) {
- mutex_lock(&inode->i_mutex);
- release_i_mutex = 1;
- }
-
- retval = filemap_write_and_wait_range(mapping, offset,
- end - 1);
- if (retval) {
- kfree(dio);
- goto out;
- }
-
- if (dio_lock_type == DIO_OWN_LOCKING) {
- mutex_unlock(&inode->i_mutex);
- acquire_i_mutex = 1;
- }
- }
-
- if (dio_lock_type == DIO_LOCKING)
- /* lockdep: not the owner will release it */
- down_read_non_owner(&inode->i_alloc_sem);
- }
-
/*
- * For file extending writes updating i_size before data
- * writeouts complete can expose uninitialized blocks. So
- * even for AIO, we need to wait for i/o to complete before
- * returning in this case.
+ * The block device state is needed in the end to finally
+ * submit everything. Since it's likely to be cache cold
+ * prefetch it here as first thing to hide some of the
+ * latency.
+ *
+ * Attempt to prefetch the pieces we likely need later.
*/
- dio->is_async = !is_sync_kiocb(iocb) && !((rw & WRITE) &&
- (end > i_size_read(inode)));
+ prefetch(&bdev->bd_disk->part_tbl);
+ prefetch(bdev->bd_queue);
+ prefetch((char *)bdev->bd_queue + SMP_CACHE_BYTES);
- retval = direct_io_worker(rw, iocb, inode, iov, offset,
- nr_segs, blkbits, get_block, end_io, dio);
+ return do_blockdev_direct_IO(rw, iocb, inode, bdev, iov, offset,
+ nr_segs, get_block, end_io,
+ submit_io, flags);
+}
- if (rw == READ && dio_lock_type == DIO_LOCKING)
- release_i_mutex = 0;
+EXPORT_SYMBOL(__blockdev_direct_IO);
-out:
- if (release_i_mutex)
- mutex_unlock(&inode->i_mutex);
- else if (acquire_i_mutex)
- mutex_lock(&inode->i_mutex);
- return retval;
+static __init int dio_init(void)
+{
+ dio_cache = KMEM_CACHE(dio, SLAB_PANIC);
+ return 0;
}
-EXPORT_SYMBOL(__blockdev_direct_IO);
+module_init(dio_init)
projects / linux-flexiantxendom0-3.2.10.git / blobdiff