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direct-io: Implement generic deferred AIO completions

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Add support to the core direct-io code to defer AIO completions to user
context using a workqueue.  This replaces opencoded and less efficient
code in XFS and ext4 (we save a memory allocation for each direct IO)
and will be needed to properly support O_(D)SYNC for AIO.

The communication between the filesystem and the direct I/O code requires
a new buffer head flag, which is a bit ugly but not avoidable until the
direct I/O code stops abusing the buffer_head structure for communicating
with the filesystems.

Currently this creates a per-superblock unbound workqueue for these
completions, which is taken from an earlier patch by Jan Kara.  I'm
not really convinced about this use and would prefer a "normal" global
workqueue with a high concurrency limit, but this needs further discussion.

JK: Fixed ext4 part, dynamic allocation of the workqueue.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Christoph Hellwig 2013-09-04 15:04:39 +02:00 committed by Al Viro
parent 4b6ccca701
commit 7b7a8665ed
11 changed files with 105 additions and 131 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

85
fs/direct-io.c
View File

@ -127,6 +127,7 @@ struct dio {
spinlock_t bio_lock; /* protects BIO fields below */
int page_errors; /* errno from get_user_pages() */
int is_async; /* is IO async ? */
bool defer_completion; /* defer AIO completion to workqueue? */
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 */
@ -141,7 +142,10 @@ struct dio {
* allocation time. Don't add new fields after pages[] unless you
* wish that they not be zeroed.
*/
struct page *pages[DIO_PAGES]; /* page buffer */
union {
struct page *pages[DIO_PAGES]; /* page buffer */
struct work_struct complete_work;/* deferred AIO completion */
};
} ____cacheline_aligned_in_smp;
static struct kmem_cache *dio_cache __read_mostly;
@ -221,16 +225,16 @@ static inline struct page *dio_get_page(struct dio *dio,
* dio_complete() - called when all DIO BIO I/O has been completed
* @offset: the byte offset in the file of the completed operation
*
* This releases locks as dictated by the locking type, lets interested parties
* know that a DIO operation has completed, and calculates the resulting return
* code for the operation.
* This drops i_dio_count, lets interested parties know that a DIO operation
* has completed, and calculates the resulting return code for the operation.
*
* It lets the filesystem know if it registered an interest earlier via
* get_block. Pass the private field of the map buffer_head so that
* filesystems can use it to hold additional state between get_block calls and
* dio_complete.
*/
static ssize_t dio_complete(struct dio *dio, loff_t offset, ssize_t ret, bool is_async)
static ssize_t dio_complete(struct dio *dio, loff_t offset, ssize_t ret,
bool is_async)
{
ssize_t transferred = 0;
@ -258,19 +262,26 @@ static ssize_t dio_complete(struct dio *dio, loff_t offset, ssize_t ret, bool is
if (ret == 0)
ret = transferred;
if (dio->end_io && dio->result) {
dio->end_io(dio->iocb, offset, transferred,
dio->private, ret, is_async);
} else {
inode_dio_done(dio->inode);
if (is_async)
aio_complete(dio->iocb, ret, 0);
}
if (dio->end_io && dio->result)
dio->end_io(dio->iocb, offset, transferred, dio->private);
inode_dio_done(dio->inode);
if (is_async)
aio_complete(dio->iocb, ret, 0);
kmem_cache_free(dio_cache, dio);
return ret;
}
static void dio_aio_complete_work(struct work_struct *work)
{
struct dio *dio = container_of(work, struct dio, complete_work);
dio_complete(dio, dio->iocb->ki_pos, 0, true);
}
static int dio_bio_complete(struct dio *dio, struct bio *bio);
/*
* Asynchronous IO callback.
*/
@ -290,8 +301,13 @@ static void dio_bio_end_aio(struct bio *bio, int error)
spin_unlock_irqrestore(&dio->bio_lock, flags);
if (remaining == 0) {
dio_complete(dio, dio->iocb->ki_pos, 0, true);
kmem_cache_free(dio_cache, dio);
if (dio->result && dio->defer_completion) {
INIT_WORK(&dio->complete_work, dio_aio_complete_work);
queue_work(dio->inode->i_sb->s_dio_done_wq,
&dio->complete_work);
} else {
dio_complete(dio, dio->iocb->ki_pos, 0, true);
}
}
}
@ -510,6 +526,41 @@ static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)
return ret;
}
/*
* Create workqueue for deferred direct IO completions. We allocate the
* workqueue when it's first needed. This avoids creating workqueue for
* filesystems that don't need it and also allows us to create the workqueue
* late enough so the we can include s_id in the name of the workqueue.
*/
static int sb_init_dio_done_wq(struct super_block *sb)
{
struct workqueue_struct *wq = alloc_workqueue("dio/%s",
WQ_MEM_RECLAIM, 0,
sb->s_id);
if (!wq)
return -ENOMEM;
/*
* This has to be atomic as more DIOs can race to create the workqueue
*/
cmpxchg(&sb->s_dio_done_wq, NULL, wq);
/* Someone created workqueue before us? Free ours... */
if (wq != sb->s_dio_done_wq)
destroy_workqueue(wq);
return 0;
}
static int dio_set_defer_completion(struct dio *dio)
{
struct super_block *sb = dio->inode->i_sb;
if (dio->defer_completion)
return 0;
dio->defer_completion = true;
if (!sb->s_dio_done_wq)
return sb_init_dio_done_wq(sb);
return 0;
}
/*
* Call into the fs to map some more disk blocks. We record the current number
* of available blocks at sdio->blocks_available. These are in units of the
@ -581,6 +632,9 @@ static int get_more_blocks(struct dio *dio, struct dio_submit *sdio,
/* Store for completion */
dio->private = map_bh->b_private;
if (ret == 0 && buffer_defer_completion(map_bh))
ret = dio_set_defer_completion(dio);
}
return ret;
}
@ -1269,7 +1323,6 @@ do_blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
if (drop_refcount(dio) == 0) {
retval = dio_complete(dio, offset, retval, false);
kmem_cache_free(dio_cache, dio);
} else
BUG_ON(retval != -EIOCBQUEUED);

11
fs/ext4/ext4.h
View File

@ -180,7 +180,6 @@ struct ext4_map_blocks {
* Flags for ext4_io_end->flags
*/
#define EXT4_IO_END_UNWRITTEN 0x0001
#define EXT4_IO_END_DIRECT 0x0002
/*
* For converting uninitialized extents on a work queue. 'handle' is used for
@ -196,8 +195,6 @@ typedef struct ext4_io_end {
unsigned int flag; /* unwritten or not */
loff_t offset; /* offset in the file */
ssize_t size; /* size of the extent */
struct kiocb *iocb; /* iocb struct for AIO */
int result; /* error value for AIO */
atomic_t count; /* reference counter */
} ext4_io_end_t;
@ -900,11 +897,9 @@ struct ext4_inode_info {
* Completed IOs that need unwritten extents handling and don't have
* transaction reserved
*/
struct list_head i_unrsv_conversion_list;
atomic_t i_ioend_count; /* Number of outstanding io_end structs */
atomic_t i_unwritten; /* Nr. of inflight conversions pending */
struct work_struct i_rsv_conversion_work;
struct work_struct i_unrsv_conversion_work;
spinlock_t i_block_reservation_lock;
@ -1276,8 +1271,6 @@ struct ext4_sb_info {
struct flex_groups *s_flex_groups;
ext4_group_t s_flex_groups_allocated;
/* workqueue for unreserved extent convertions (dio) */
struct workqueue_struct *unrsv_conversion_wq;
/* workqueue for reserved extent conversions (buffered io) */
struct workqueue_struct *rsv_conversion_wq;
@ -1340,9 +1333,6 @@ static inline void ext4_set_io_unwritten_flag(struct inode *inode,
struct ext4_io_end *io_end)
{
if (!(io_end->flag & EXT4_IO_END_UNWRITTEN)) {
/* Writeback has to have coversion transaction reserved */
WARN_ON(EXT4_SB(inode->i_sb)->s_journal && !io_end->handle &&
!(io_end->flag & EXT4_IO_END_DIRECT));
io_end->flag |= EXT4_IO_END_UNWRITTEN;
atomic_inc(&EXT4_I(inode)->i_unwritten);
}
@ -2716,7 +2706,6 @@ extern void ext4_put_io_end_defer(ext4_io_end_t *io_end);
extern void ext4_io_submit_init(struct ext4_io_submit *io,
struct writeback_control *wbc);
extern void ext4_end_io_rsv_work(struct work_struct *work);
extern void ext4_end_io_unrsv_work(struct work_struct *work);
extern void ext4_io_submit(struct ext4_io_submit *io);
extern int ext4_bio_write_page(struct ext4_io_submit *io,
struct page *page,

28
fs/ext4/inode.c
View File

@ -727,8 +727,12 @@ static int _ext4_get_block(struct inode *inode, sector_t iblock,
ret = ext4_map_blocks(handle, inode, &map, flags);
if (ret > 0) {
ext4_io_end_t *io_end = ext4_inode_aio(inode);
map_bh(bh, inode->i_sb, map.m_pblk);
bh->b_state = (bh->b_state & ~EXT4_MAP_FLAGS) | map.m_flags;
if (io_end && io_end->flag & EXT4_IO_END_UNWRITTEN)
set_buffer_defer_completion(bh);
bh->b_size = inode->i_sb->s_blocksize * map.m_len;
ret = 0;
}
@ -2991,19 +2995,13 @@ static int ext4_get_block_write_nolock(struct inode *inode, sector_t iblock,
}
static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
ssize_t size, void *private, int ret,
bool is_async)
ssize_t size, void *private)
{
struct inode *inode = file_inode(iocb->ki_filp);
ext4_io_end_t *io_end = iocb->private;
/* if not async direct IO just return */
if (!io_end) {
inode_dio_done(inode);
if (is_async)
aio_complete(iocb, ret, 0);
if (!io_end)
return;
}
ext_debug("ext4_end_io_dio(): io_end 0x%p "
"for inode %lu, iocb 0x%p, offset %llu, size %zd\n",
@ -3013,11 +3011,7 @@ static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
iocb->private = NULL;
io_end->offset = offset;
io_end->size = size;
if (is_async) {
io_end->iocb = iocb;
io_end->result = ret;
}
ext4_put_io_end_defer(io_end);
ext4_put_io_end(io_end);
}
/*
@ -3102,7 +3096,6 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb,
ret = -ENOMEM;
goto retake_lock;
}
io_end->flag |= EXT4_IO_END_DIRECT;
/*
* Grab reference for DIO. Will be dropped in ext4_end_io_dio()
*/
@ -3147,13 +3140,6 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb,
if (ret <= 0 && ret != -EIOCBQUEUED && iocb->private) {
WARN_ON(iocb->private != io_end);
WARN_ON(io_end->flag & EXT4_IO_END_UNWRITTEN);
WARN_ON(io_end->iocb);
/*
* Generic code already did inode_dio_done() so we
* have to clear EXT4_IO_END_DIRECT to not do it for
* the second time.
*/
io_end->flag = 0;
ext4_put_io_end(io_end);
iocb->private = NULL;
}

30
fs/ext4/page-io.c
View File

@ -123,10 +123,6 @@ static void ext4_release_io_end(ext4_io_end_t *io_end)
ext4_finish_bio(bio);
bio_put(bio);
}
if (io_end->flag & EXT4_IO_END_DIRECT)
inode_dio_done(io_end->inode);
if (io_end->iocb)
aio_complete(io_end->iocb, io_end->result, 0);
kmem_cache_free(io_end_cachep, io_end);
}
@ -204,19 +200,14 @@ static void ext4_add_complete_io(ext4_io_end_t *io_end)
struct workqueue_struct *wq;
unsigned long flags;
BUG_ON(!(io_end->flag & EXT4_IO_END_UNWRITTEN));
/* Only reserved conversions from writeback should enter here */
WARN_ON(!(io_end->flag & EXT4_IO_END_UNWRITTEN));
WARN_ON(!io_end->handle);
spin_lock_irqsave(&ei->i_completed_io_lock, flags);
if (io_end->handle) {
wq = EXT4_SB(io_end->inode->i_sb)->rsv_conversion_wq;
if (list_empty(&ei->i_rsv_conversion_list))
queue_work(wq, &ei->i_rsv_conversion_work);
list_add_tail(&io_end->list, &ei->i_rsv_conversion_list);
} else {
wq = EXT4_SB(io_end->inode->i_sb)->unrsv_conversion_wq;
if (list_empty(&ei->i_unrsv_conversion_list))
queue_work(wq, &ei->i_unrsv_conversion_work);
list_add_tail(&io_end->list, &ei->i_unrsv_conversion_list);
}
wq = EXT4_SB(io_end->inode->i_sb)->rsv_conversion_wq;
if (list_empty(&ei->i_rsv_conversion_list))
queue_work(wq, &ei->i_rsv_conversion_work);
list_add_tail(&io_end->list, &ei->i_rsv_conversion_list);
spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
}
@ -256,13 +247,6 @@ void ext4_end_io_rsv_work(struct work_struct *work)
ext4_do_flush_completed_IO(&ei->vfs_inode, &ei->i_rsv_conversion_list);
}
void ext4_end_io_unrsv_work(struct work_struct *work)
{
struct ext4_inode_info *ei = container_of(work, struct ext4_inode_info,
i_unrsv_conversion_work);
ext4_do_flush_completed_IO(&ei->vfs_inode, &ei->i_unrsv_conversion_list);
}
ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags)
{
ext4_io_end_t *io = kmem_cache_zalloc(io_end_cachep, flags);

16
fs/ext4/super.c
View File

@ -762,9 +762,7 @@ static void ext4_put_super(struct super_block *sb)
ext4_unregister_li_request(sb);
dquot_disable(sb, -1, DQUOT_USAGE_ENABLED | DQUOT_LIMITS_ENABLED);
flush_workqueue(sbi->unrsv_conversion_wq);
flush_workqueue(sbi->rsv_conversion_wq);
destroy_workqueue(sbi->unrsv_conversion_wq);
destroy_workqueue(sbi->rsv_conversion_wq);
if (sbi->s_journal) {
@ -875,14 +873,12 @@ static struct inode *ext4_alloc_inode(struct super_block *sb)
#endif
ei->jinode = NULL;
INIT_LIST_HEAD(&ei->i_rsv_conversion_list);
INIT_LIST_HEAD(&ei->i_unrsv_conversion_list);
spin_lock_init(&ei->i_completed_io_lock);
ei->i_sync_tid = 0;
ei->i_datasync_tid = 0;
atomic_set(&ei->i_ioend_count, 0);
atomic_set(&ei->i_unwritten, 0);
INIT_WORK(&ei->i_rsv_conversion_work, ext4_end_io_rsv_work);
INIT_WORK(&ei->i_unrsv_conversion_work, ext4_end_io_unrsv_work);
return &ei->vfs_inode;
}
@ -3954,14 +3950,6 @@ no_journal:
goto failed_mount4;
}
EXT4_SB(sb)->unrsv_conversion_wq =
alloc_workqueue("ext4-unrsv-conversion", WQ_MEM_RECLAIM | WQ_UNBOUND, 1);
if (!EXT4_SB(sb)->unrsv_conversion_wq) {
printk(KERN_ERR "EXT4-fs: failed to create workqueue\n");
ret = -ENOMEM;
goto failed_mount4;
}
/*
* The jbd2_journal_load will have done any necessary log recovery,
* so we can safely mount the rest of the filesystem now.
@ -4115,8 +4103,6 @@ failed_mount4:
ext4_msg(sb, KERN_ERR, "mount failed");
if (EXT4_SB(sb)->rsv_conversion_wq)
destroy_workqueue(EXT4_SB(sb)->rsv_conversion_wq);
if (EXT4_SB(sb)->unrsv_conversion_wq)
destroy_workqueue(EXT4_SB(sb)->unrsv_conversion_wq);
failed_mount_wq:
if (sbi->s_journal) {
jbd2_journal_destroy(sbi->s_journal);
@ -4564,7 +4550,6 @@ static int ext4_sync_fs(struct super_block *sb, int wait)
trace_ext4_sync_fs(sb, wait);
flush_workqueue(sbi->rsv_conversion_wq);
flush_workqueue(sbi->unrsv_conversion_wq);
/*
* Writeback quota in non-journalled quota case - journalled quota has
* no dirty dquots
@ -4600,7 +4585,6 @@ static int ext4_sync_fs_nojournal(struct super_block *sb, int wait)
trace_ext4_sync_fs(sb, wait);
flush_workqueue(EXT4_SB(sb)->rsv_conversion_wq);
flush_workqueue(EXT4_SB(sb)->unrsv_conversion_wq);
dquot_writeback_dquots(sb, -1);
if (wait && test_opt(sb, BARRIER))
ret = blkdev_issue_flush(sb->s_bdev, GFP_KERNEL, NULL);

8
fs/ocfs2/aops.c
View File

@ -565,9 +565,7 @@ bail:
static void ocfs2_dio_end_io(struct kiocb *iocb,
loff_t offset,
ssize_t bytes,
void *private,
int ret,
bool is_async)
void *private)
{
struct inode *inode = file_inode(iocb->ki_filp);
int level;
@ -592,10 +590,6 @@ static void ocfs2_dio_end_io(struct kiocb *iocb,
level = ocfs2_iocb_rw_locked_level(iocb);
ocfs2_rw_unlock(inode, level);
inode_dio_done(inode);
if (is_async)
aio_complete(iocb, ret, 0);
}
/*

18
fs/super.c
View File

@ -152,15 +152,9 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags)
static const struct super_operations default_op;
if (s) {
if (security_sb_alloc(s)) {
/*
* We cannot call security_sb_free() without
* security_sb_alloc() succeeding. So bail out manually
*/
kfree(s);
s = NULL;
goto out;
}
if (security_sb_alloc(s))
goto out_free_sb;
#ifdef CONFIG_SMP
s->s_files = alloc_percpu(struct list_head);
if (!s->s_files)
@ -228,6 +222,7 @@ err_out:
free_percpu(s->s_files);
#endif
destroy_sb_writers(s);
out_free_sb:
kfree(s);
s = NULL;
goto out;
@ -414,6 +409,11 @@ void generic_shutdown_super(struct super_block *sb)
evict_inodes(sb);
if (sb->s_dio_done_wq) {
destroy_workqueue(sb->s_dio_done_wq);
sb->s_dio_done_wq = NULL;
}
if (sop->put_super)
sop->put_super(sb);

28
fs/xfs/xfs_aops.c
View File

@ -86,14 +86,6 @@ xfs_destroy_ioend(
bh->b_end_io(bh, !ioend->io_error);
}
if (ioend->io_iocb) {
inode_dio_done(ioend->io_inode);
if (ioend->io_isasync) {
aio_complete(ioend->io_iocb, ioend->io_error ?
ioend->io_error : ioend->io_result, 0);
}
}
mempool_free(ioend, xfs_ioend_pool);
}
@ -281,7 +273,6 @@ xfs_alloc_ioend(
* all the I/O from calling the completion routine too early.
*/
atomic_set(&ioend->io_remaining, 1);
ioend->io_isasync = 0;
ioend->io_isdirect = 0;
ioend->io_error = 0;
ioend->io_list = NULL;
@ -291,8 +282,6 @@ xfs_alloc_ioend(
ioend->io_buffer_tail = NULL;
ioend->io_offset = 0;
ioend->io_size = 0;
ioend->io_iocb = NULL;
ioend->io_result = 0;
ioend->io_append_trans = NULL;
INIT_WORK(&ioend->io_work, xfs_end_io);
@ -1292,8 +1281,10 @@ __xfs_get_blocks(
if (create || !ISUNWRITTEN(&imap))
xfs_map_buffer(inode, bh_result, &imap, offset);
if (create && ISUNWRITTEN(&imap)) {
if (direct)
if (direct) {
bh_result->b_private = inode;
set_buffer_defer_completion(bh_result);
}
set_buffer_unwritten(bh_result);
}
}
@ -1390,9 +1381,7 @@ xfs_end_io_direct_write(
struct kiocb *iocb,
loff_t offset,
ssize_t size,
void *private,
int ret,
bool is_async)
void *private)
{
struct xfs_ioend *ioend = iocb->private;
@ -1414,17 +1403,10 @@ xfs_end_io_direct_write(
ioend->io_offset = offset;
ioend->io_size = size;
ioend->io_iocb = iocb;
ioend->io_result = ret;
if (private && size > 0)
ioend->io_type = XFS_IO_UNWRITTEN;
if (is_async) {
ioend->io_isasync = 1;
xfs_finish_ioend(ioend);
} else {
xfs_finish_ioend_sync(ioend);
}
xfs_finish_ioend_sync(ioend);
}
STATIC ssize_t

3
fs/xfs/xfs_aops.h
View File

@ -45,7 +45,6 @@ typedef struct xfs_ioend {
unsigned int io_type; /* delalloc / unwritten */
int io_error; /* I/O error code */
atomic_t io_remaining; /* hold count */
unsigned int io_isasync : 1; /* needs aio_complete */
unsigned int io_isdirect : 1;/* direct I/O */
struct inode *io_inode; /* file being written to */
struct buffer_head *io_buffer_head;/* buffer linked list head */
@ -54,8 +53,6 @@ typedef struct xfs_ioend {
xfs_off_t io_offset; /* offset in the file */
struct work_struct io_work; /* xfsdatad work queue */
struct xfs_trans *io_append_trans;/* xact. for size update */
struct kiocb *io_iocb;
int io_result;
} xfs_ioend_t;
extern const struct address_space_operations xfs_address_space_operations;

2
include/linux/buffer_head.h
View File

@ -36,6 +36,7 @@ enum bh_state_bits {
BH_Quiet, /* Buffer Error Prinks to be quiet */
BH_Meta, /* Buffer contains metadata */
BH_Prio, /* Buffer should be submitted with REQ_PRIO */
BH_Defer_Completion, /* Defer AIO completion to workqueue */
BH_PrivateStart,/* not a state bit, but the first bit available
* for private allocation by other entities
@ -128,6 +129,7 @@ BUFFER_FNS(Write_EIO, write_io_error)
BUFFER_FNS(Unwritten, unwritten)
BUFFER_FNS(Meta, meta)
BUFFER_FNS(Prio, prio)
BUFFER_FNS(Defer_Completion, defer_completion)
#define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK)

7
include/linux/fs.h
View File

@ -46,6 +46,7 @@ struct vfsmount;
struct cred;
struct swap_info_struct;
struct seq_file;
struct workqueue_struct;
extern void __init inode_init(void);
extern void __init inode_init_early(void);
@ -63,8 +64,7 @@ struct buffer_head;
typedef int (get_block_t)(struct inode *inode, sector_t iblock,
struct buffer_head *bh_result, int create);
typedef void (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
ssize_t bytes, void *private, int ret,
bool is_async);
ssize_t bytes, void *private);
#define MAY_EXEC 0x00000001
#define MAY_WRITE 0x00000002
@ -1328,6 +1328,9 @@ struct super_block {
/* Being remounted read-only */
int s_readonly_remount;
/* AIO completions deferred from interrupt context */
struct workqueue_struct *s_dio_done_wq;
};
/* superblock cache pruning functions */