[PATCH 4/8] btrfs: Switch to iomap_dio_rw() for dio

Goldwyn Rodrigues
2019-12-13T20:41:12Z

From: Goldwyn Rodrigues <rgoldwyn@suse.com>

Switch from __blockdev_direct_IO() to iomap_dio_rw().
Rename btrfs_get_blocks_direct() to btrfs_dio_iomap_begin() and use it
as iomap_begin() for iomap direct I/O functions. This function
allocates and locks all the blocks required for the I/O.
btrfs_submit_direct() is used as the submit_io() hook for direct I/O
ops.

Since we need direct I/O reads to go through iomap_dio_rw(), we change
file_operations.read_iter() to a btrfs_file_read_iter() which calls
btrfs_direct_IO() for direct reads and falls back to
generic_file_buffered_read() for incomplete reads and buffered reads.

We don't need address_space.direct_IO() anymore so set it to noop.
Similarly, we don't need flags used in __blockdev_direct_IO(). iomap is
capable of direct I/O reads from a hole, so we don't need to return
-ENOENT.

BTRFS direct I/O is now done under i_rwsem, shared in case of
reads and exclusive in case of writes. This guards against simultaneous
truncates.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
---
fs/btrfs/ctree.h | 1 +
fs/btrfs/file.c | 21 +++++-
fs/btrfs/inode.c | 192 ++++++++++++++++++++++++++-----------------------------
3 files changed, 110 insertions(+), 104 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index b2e8fd8a8e59..113dcd1a11cd 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2904,6 +2904,7 @@ int btrfs_writepage_cow_fixup(struct page *page, u64 start, u64 end);
void btrfs_writepage_endio_finish_ordered(struct page *page, u64 start,
u64 end, int uptodate);
extern const struct dentry_operations btrfs_dentry_operations;
+ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter);

/* ioctl.c */
long btrfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 0cb43b682789..7010dd7beccc 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1832,7 +1832,7 @@ static ssize_t __btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from)
loff_t endbyte;
int err;

- written = generic_file_direct_write(iocb, from);
+ written = btrfs_direct_IO(iocb, from);

if (written < 0 || !iov_iter_count(from))
return written;
@@ -3444,9 +3444,26 @@ static int btrfs_file_open(struct inode *inode, struct file *filp)
return generic_file_open(inode, filp);
}

+static ssize_t btrfs_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+ ssize_t ret = 0;
+
+ if (iocb->ki_flags & IOCB_DIRECT) {
+ struct inode *inode = file_inode(iocb->ki_filp);
+
+ inode_lock_shared(inode);
+ ret = btrfs_direct_IO(iocb, to);
+ inode_unlock_shared(inode);
+ if (ret < 0)
+ return ret;
+ }
+
+ return generic_file_buffered_read(iocb, to, ret);
+}
+
const struct file_operations btrfs_file_operations = {
.llseek = btrfs_file_llseek,
- .read_iter = generic_file_read_iter,
+ .read_iter = btrfs_file_read_iter,
.splice_read = generic_file_splice_read,
.write_iter = btrfs_file_write_iter,
.mmap = btrfs_file_mmap,
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 56032c518b26..ff5ee99086f0 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -29,6 +29,7 @@
#include <linux/iversion.h>
#include <linux/swap.h>
#include <linux/sched/mm.h>
+#include <linux/iomap.h>
#include <asm/unaligned.h>
#include "misc.h"
#include "ctree.h"
@@ -7510,7 +7511,7 @@ noinline int can_nocow_extent(struct inode *inode, u64 offset, u64 *len,
}

static int lock_extent_direct(struct inode *inode, u64 lockstart, u64 lockend,
- struct extent_state **cached_state, int writing)
+ struct extent_state **cached_state, bool writing)
{
struct btrfs_ordered_extent *ordered;
int ret = 0;
@@ -7648,30 +7649,7 @@ static struct extent_map *create_io_em(struct inode *inode, u64 start, u64 len,
}

-static int btrfs_get_blocks_direct_read(struct extent_map *em,
- struct buffer_head *bh_result,
- struct inode *inode,
- u64 start, u64 len)
-{
- struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
-
- if (em->block_start == EXTENT_MAP_HOLE ||
- test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
- return -ENOENT;
-
- len = min(len, em->len - (start - em->start));
-
- bh_result->b_blocknr = (em->block_start + (start - em->start)) >>
- inode->i_blkbits;
- bh_result->b_size = len;
- bh_result->b_bdev = fs_info->fs_devices->latest_bdev;
- set_buffer_mapped(bh_result);
-
- return 0;
-}
-
static int btrfs_get_blocks_direct_write(struct extent_map **map,
- struct buffer_head *bh_result,
struct inode *inode,
struct btrfs_dio_data *dio_data,
u64 start, u64 len)
@@ -7733,7 +7711,6 @@ static int btrfs_get_blocks_direct_write(struct extent_map **map,
}

/* this will cow the extent */
- len = bh_result->b_size;
free_extent_map(em);
*map = em = btrfs_new_extent_direct(inode, start, len);
if (IS_ERR(em)) {
@@ -7744,15 +7721,6 @@ static int btrfs_get_blocks_direct_write(struct extent_map **map,
len = min(len, em->len - (start - em->start));

skip_cow:
- bh_result->b_blocknr = (em->block_start + (start - em->start)) >>
- inode->i_blkbits;
- bh_result->b_size = len;
- bh_result->b_bdev = fs_info->fs_devices->latest_bdev;
- set_buffer_mapped(bh_result);
-
- if (!test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
- set_buffer_new(bh_result);
-
/*
* Need to update the i_size under the extent lock so buffered
* readers will get the updated i_size when we unlock.
@@ -7768,24 +7736,37 @@ static int btrfs_get_blocks_direct_write(struct extent_map **map,
return ret;
}

-static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
- struct buffer_head *bh_result, int create)
+static int btrfs_dio_iomap_begin(struct inode *inode, loff_t start,
+ loff_t length, unsigned flags, struct iomap *iomap,
+ struct iomap *srcmap)
{
struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
struct extent_map *em;
struct extent_state *cached_state = NULL;
struct btrfs_dio_data *dio_data = NULL;
- u64 start = iblock << inode->i_blkbits;
u64 lockstart, lockend;
- u64 len = bh_result->b_size;
+ bool write = !!(flags & IOMAP_WRITE);
int ret = 0;
+ u64 len = length;
+ bool unlock_extents = false;

- if (!create)
+ if (!write)
len = min_t(u64, len, fs_info->sectorsize);

lockstart = start;
lockend = start + len - 1;

+ /*
+ * The generic stuff only does filemap_write_and_wait_range, which
+ * isn't enough if we've written compressed pages to this area, so
+ * we need to flush the dirty pages again to make absolutely sure
+ * that any outstanding dirty pages are on disk.
+ */
+ if (test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT,
+ &BTRFS_I(inode)->runtime_flags))
+ ret = filemap_fdatawrite_range(inode->i_mapping, start,
+ start + length - 1);
+
if (current->journal_info) {
/*
* Need to pull our outstanding extents and set journal_info to NULL so
@@ -7801,7 +7782,7 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
* this range and we need to fallback to buffered.
*/
if (lock_extent_direct(inode, lockstart, lockend, &cached_state,
- create)) {
+ write)) {
ret = -ENOTBLK;
goto err;
}
@@ -7833,35 +7814,52 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
goto unlock_err;
}

- if (create) {
- ret = btrfs_get_blocks_direct_write(&em, bh_result, inode,
+ len = min(len, em->len - (start - em->start));
+ if (write) {
+ ret = btrfs_get_blocks_direct_write(&em, inode,
dio_data, start, len);
if (ret < 0)
goto unlock_err;
-
- unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart,
- lockend, &cached_state);
+ unlock_extents = true;
+ /* Recalc len in case the new em is smaller than requested */
+ len = min(len, em->len - (start - em->start));
+ } else if (em->block_start == EXTENT_MAP_HOLE ||
+ test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) {
+ /* Unlock in case of direct reading from a hole */
+ unlock_extents = true;
} else {
- ret = btrfs_get_blocks_direct_read(em, bh_result, inode,
- start, len);
- /* Can be negative only if we read from a hole */
- if (ret < 0) {
- ret = 0;
- free_extent_map(em);
- goto unlock_err;
- }
/*
* We need to unlock only the end area that we aren't using.
* The rest is going to be unlocked by the endio routine.
*/
- lockstart = start + bh_result->b_size;
- if (lockstart < lockend) {
- unlock_extent_cached(&BTRFS_I(inode)->io_tree,
- lockstart, lockend, &cached_state);
- } else {
- free_extent_state(cached_state);
- }
+ lockstart = start + len;
+ if (lockstart < lockend)
+ unlock_extents = true;
+ }
+
+ if (unlock_extents)
+ unlock_extent_cached(&BTRFS_I(inode)->io_tree,
+ lockstart, lockend, &cached_state);
+ else
+ free_extent_state(cached_state);
+
+ /*
+ * Translate extent map information to iomap
+ * We trim the extents (and move the addr) even though
+ * iomap code does that, since we have locked only the parts
+ * we are performing I/O in.
+ */
+ if ((em->block_start == EXTENT_MAP_HOLE) ||
+ (test_bit(EXTENT_FLAG_PREALLOC, &em->flags) && !write)) {
+ iomap->addr = IOMAP_NULL_ADDR;
+ iomap->type = IOMAP_HOLE;
+ } else {
+ iomap->addr = em->block_start + (start - em->start);
+ iomap->type = IOMAP_MAPPED;
}
+ iomap->offset = start;
+ iomap->bdev = fs_info->fs_devices->latest_bdev;
+ iomap->length = len;

free_extent_map(em);

@@ -8229,10 +8227,9 @@ static void btrfs_endio_direct_read(struct bio *bio)

kfree(dip);

- dio_bio->bi_status = err;
- dio_end_io(dio_bio);
btrfs_io_bio_free_csum(io_bio);
- bio_put(bio);
+ dio_bio->bi_status = err;
+ bio_endio(dio_bio);
}

static void __endio_write_update_ordered(struct inode *inode,
@@ -8289,8 +8286,7 @@ static void btrfs_endio_direct_write(struct bio *bio)
kfree(dip);

dio_bio->bi_status = bio->bi_status;
- dio_end_io(dio_bio);
- bio_put(bio);
+ bio_endio(dio_bio);
}

static blk_status_t btrfs_submit_bio_start_direct_io(void *private_data,
@@ -8522,9 +8518,10 @@ static int btrfs_submit_direct_hook(struct btrfs_dio_private *dip)
return 0;
}

-static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
+static blk_qc_t btrfs_submit_direct(struct bio *dio_bio, struct file *file,
loff_t file_offset)
{
+ struct inode *inode = file_inode(file);
struct btrfs_dio_private *dip = NULL;
struct bio *bio = NULL;
struct btrfs_io_bio *io_bio;
@@ -8575,7 +8572,7 @@ static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,

ret = btrfs_submit_direct_hook(dip);
if (!ret)
- return;
+ return BLK_QC_T_NONE;

btrfs_io_bio_free_csum(io_bio);

@@ -8594,7 +8591,7 @@ static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
/*
* The end io callbacks free our dip, do the final put on bio
* and all the cleanup and final put for dio_bio (through
- * dio_end_io()).
+ * end_io()).
*/
dip = NULL;
bio = NULL;
@@ -8609,15 +8606,12 @@ static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
file_offset + dio_bio->bi_iter.bi_size - 1);

dio_bio->bi_status = BLK_STS_IOERR;
- /*
- * Releases and cleans up our dio_bio, no need to bio_put()
- * nor bio_endio()/bio_io_error() against dio_bio.
- */
- dio_end_io(dio_bio);
+ bio_endio(dio_bio);
}
if (bio)
bio_put(bio);
kfree(dip);
+ return BLK_QC_T_NONE;
}

static ssize_t check_direct_IO(struct btrfs_fs_info *fs_info,
@@ -8653,7 +8647,23 @@ static ssize_t check_direct_IO(struct btrfs_fs_info *fs_info,
return retval;
}

-static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
+static const struct iomap_ops btrfs_dio_iomap_ops = {
+ .iomap_begin = btrfs_dio_iomap_begin,
+};
+
+static const struct iomap_dio_ops btrfs_dops = {
+ .submit_io = btrfs_submit_direct,
+};
+
+
+/*
+ * btrfs_direct_IO - perform direct I/O
+ * inode->i_rwsem must be locked before calling this function, shared or exclusive.
+ * @iocb - kernel iocb
+ * @iter - iter to/from data is copied
+ */
+
+ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file->f_mapping->host;
@@ -8662,28 +8672,15 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
struct extent_changeset *data_reserved = NULL;
loff_t offset = iocb->ki_pos;
size_t count = 0;
- int flags = 0;
- bool wakeup = true;
bool relock = false;
ssize_t ret;

+ lockdep_assert_held(&inode->i_rwsem);
+
if (check_direct_IO(fs_info, iter, offset))
return 0;

- inode_dio_begin(inode);
-
- /*
- * The generic stuff only does filemap_write_and_wait_range, which
- * isn't enough if we've written compressed pages to this area, so
- * we need to flush the dirty pages again to make absolutely sure
- * that any outstanding dirty pages are on disk.
- */
count = iov_iter_count(iter);
- if (test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT,
- &BTRFS_I(inode)->runtime_flags))
- filemap_fdatawrite_range(inode->i_mapping, offset,
- offset + count - 1);
-
if (iov_iter_rw(iter) == WRITE) {
/*
* If the write DIO is beyond the EOF, we need update
@@ -8714,17 +8711,11 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
dio_data.unsubmitted_oe_range_end = (u64)offset;
current->journal_info = &dio_data;
down_read(&BTRFS_I(inode)->dio_sem);
- } else if (test_bit(BTRFS_INODE_READDIO_NEED_LOCK,
- &BTRFS_I(inode)->runtime_flags)) {
- inode_dio_end(inode);
- flags = DIO_LOCKING | DIO_SKIP_HOLES;
- wakeup = false;
}

- ret = __blockdev_direct_IO(iocb, inode,
- fs_info->fs_devices->latest_bdev,
- iter, btrfs_get_blocks_direct, NULL,
- btrfs_submit_direct, flags);
+ ret = iomap_dio_rw(iocb, iter, &btrfs_dio_iomap_ops, &btrfs_dops,
+ is_sync_kiocb(iocb));
+
if (iov_iter_rw(iter) == WRITE) {
up_read(&BTRFS_I(inode)->dio_sem);
current->journal_info = NULL;
@@ -8751,11 +8742,8 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
btrfs_delalloc_release_extents(BTRFS_I(inode), count);
}
out:
- if (wakeup)
- inode_dio_end(inode);
if (relock)
inode_lock(inode);
-
extent_changeset_free(data_reserved);
return ret;
}
@@ -11045,7 +11033,7 @@ static const struct address_space_operations btrfs_aops = {
.writepage = btrfs_writepage,
.writepages = btrfs_writepages,
.readpages = btrfs_readpages,
- .direct_IO = btrfs_direct_IO,
+ .direct_IO = noop_direct_IO,
.invalidatepage = btrfs_invalidatepage,
.releasepage = btrfs_releasepage,
.set_page_dirty = btrfs_set_page_dirty,
--
2.16.4