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[PATCH] Kill PF_SYNCWRITE flag

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A process flag to indicate whether we are doing sync io is incredibly
ugly. It also causes performance problems when one does a lot of async
io and then proceeds to sync it. Part of the io will go out as async,
and the other part as sync. This causes a disconnect between the
previously submitted io and the synced io. For io schedulers such as CFQ,
this will cause us lost merges and suboptimal behaviour in scheduling.

Remove PF_SYNCWRITE completely from the fsync/msync paths, and let
the O_DIRECT path just directly indicate that the writes are sync
by using WRITE_SYNC instead.

Signed-off-by: Jens Axboe <axboe@suse.de>
This commit is contained in:
Jens Axboe 2006-06-13 08:26:10 +02:00 committed by Jens Axboe
parent 271f18f102
commit b31dc66a54
10 changed files with 20 additions and 29 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
block/as-iosched.c
View file

@ -1339,7 +1339,7 @@ static void as_add_request(request_queue_t *q, struct request *rq)
arq->state = AS_RQ_NEW;
if (rq_data_dir(arq->request) == READ
|| current->flags&PF_SYNCWRITE)
|| (arq->request->flags & REQ_RW_SYNC))
arq->is_sync = 1;
else
arq->is_sync = 0;

4
block/cfq-iosched.c
View file

@ -277,8 +277,6 @@ static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned int, unsi
static void cfq_dispatch_insert(request_queue_t *, struct cfq_rq *);
static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, gfp_t gfp_mask);
#define process_sync(tsk) ((tsk)->flags & PF_SYNCWRITE)
/*
* lots of deadline iosched dupes, can be abstracted later...
*/
@ -334,7 +332,7 @@ static int cfq_queue_empty(request_queue_t *q)
static inline pid_t cfq_queue_pid(struct task_struct *task, int rw)
{
if (rw == READ || process_sync(task))
if (rw == READ || rw == WRITE_SYNC)
return task->pid;
return CFQ_KEY_ASYNC;

3
block/ll_rw_blk.c
View file

@ -2827,6 +2827,9 @@ static void init_request_from_bio(struct request *req, struct bio *bio)
if (unlikely(bio_barrier(bio)))
req->flags |= (REQ_HARDBARRIER | REQ_NOMERGE);
if (bio_sync(bio))
req->flags |= REQ_RW_SYNC;
req->errors = 0;
req->hard_sector = req->sector = bio->bi_sector;
req->hard_nr_sectors = req->nr_sectors = bio_sectors(bio);

2
drivers/usb/gadget/file_storage.c
View file

@ -1906,7 +1906,6 @@ static int fsync_sub(struct lun *curlun)
inode = filp->f_dentry->d_inode;
mutex_lock(&inode->i_mutex);
current->flags |= PF_SYNCWRITE;
rc = filemap_fdatawrite(inode->i_mapping);
err = filp->f_op->fsync(filp, filp->f_dentry, 1);
if (!rc)
@ -1914,7 +1913,6 @@ static int fsync_sub(struct lun *curlun)
err = filemap_fdatawait(inode->i_mapping);
if (!rc)
rc = err;
current->flags &= ~PF_SYNCWRITE;
mutex_unlock(&inode->i_mutex);
VLDBG(curlun, "fdatasync -> %d\n", rc);
return rc;

2
fs/buffer.c
View file

@ -331,7 +331,6 @@ long do_fsync(struct file *file, int datasync)
goto out;
}
current->flags |= PF_SYNCWRITE;
ret = filemap_fdatawrite(mapping);
/*
@ -346,7 +345,6 @@ long do_fsync(struct file *file, int datasync)
err = filemap_fdatawait(mapping);
if (!ret)
ret = err;
current->flags &= ~PF_SYNCWRITE;
out:
return ret;
}

18
fs/direct-io.c
View file

@ -162,7 +162,7 @@ static int dio_refill_pages(struct dio *dio)
NULL); /* vmas */
up_read(&current->mm->mmap_sem);
if (ret < 0 && dio->blocks_available && (dio->rw == WRITE)) {
if (ret < 0 && dio->blocks_available && (dio->rw & WRITE)) {
struct page *page = ZERO_PAGE(dio->curr_user_address);
/*
* A memory fault, but the filesystem has some outstanding
@ -535,7 +535,7 @@ static int get_more_blocks(struct dio *dio)
map_bh->b_state = 0;
map_bh->b_size = fs_count << dio->inode->i_blkbits;
create = dio->rw == WRITE;
create = dio->rw & WRITE;
if (dio->lock_type == DIO_LOCKING) {
if (dio->block_in_file < (i_size_read(dio->inode) >>
dio->blkbits))
@ -867,7 +867,7 @@ do_holes:
loff_t i_size_aligned;
/* AKPM: eargh, -ENOTBLK is a hack */
if (dio->rw == WRITE) {
if (dio->rw & WRITE) {
page_cache_release(page);
return -ENOTBLK;
}
@ -1045,7 +1045,7 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
}
} /* end iovec loop */
if (ret == -ENOTBLK && rw == WRITE) {
if (ret == -ENOTBLK && (rw & WRITE)) {
/*
* The remaining part of the request will be
* be handled by buffered I/O when we return
@ -1089,7 +1089,7 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
if (dio->is_async) {
int should_wait = 0;
if (dio->result < dio->size && rw == WRITE) {
if (dio->result < dio->size && (rw & WRITE)) {
dio->waiter = current;
should_wait = 1;
}
@ -1142,7 +1142,7 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
ret = transferred;
/* We could have also come here on an AIO file extend */
if (!is_sync_kiocb(iocb) && rw == WRITE &&
if (!is_sync_kiocb(iocb) && (rw & WRITE) &&
ret >= 0 && dio->result == dio->size)
/*
* For AIO writes where we have completed the
@ -1194,7 +1194,7 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
int acquire_i_mutex = 0;
if (rw & WRITE)
current->flags |= PF_SYNCWRITE;
rw = WRITE_SYNC;
if (bdev)
bdev_blkbits = blksize_bits(bdev_hardsect_size(bdev));
@ -1270,7 +1270,7 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
* 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) &&
dio->is_async = !is_sync_kiocb(iocb) && !((rw & WRITE) &&
(end > i_size_read(inode)));
retval = direct_io_worker(rw, iocb, inode, iov, offset,
@ -1284,8 +1284,6 @@ out:
mutex_unlock(&inode->i_mutex);
else if (acquire_i_mutex)
mutex_lock(&inode->i_mutex);
if (rw & WRITE)
current->flags &= ~PF_SYNCWRITE;
return retval;
}
EXPORT_SYMBOL(__blockdev_direct_IO);

2
fs/fs-writeback.c
View file

@ -623,7 +623,6 @@ int generic_osync_inode(struct inode *inode, struct address_space *mapping, int
int need_write_inode_now = 0;
int err2;
current->flags |= PF_SYNCWRITE;
if (what & OSYNC_DATA)
err = filemap_fdatawrite(mapping);
if (what & (OSYNC_METADATA|OSYNC_DATA)) {
@ -636,7 +635,6 @@ int generic_osync_inode(struct inode *inode, struct address_space *mapping, int
if (!err)
err = err2;
}
current->flags &= ~PF_SYNCWRITE;
spin_lock(&inode_lock);
if ((inode->i_state & I_DIRTY) &&

2
include/linux/blkdev.h
View file

@ -241,6 +241,7 @@ enum rq_flag_bits {
__REQ_PM_RESUME, /* resume request */
__REQ_PM_SHUTDOWN, /* shutdown request */
__REQ_ORDERED_COLOR, /* is before or after barrier */
__REQ_RW_SYNC, /* request is sync (O_DIRECT) */
__REQ_NR_BITS, /* stops here */
};
@ -270,6 +271,7 @@ enum rq_flag_bits {
#define REQ_PM_RESUME (1 << __REQ_PM_RESUME)
#define REQ_PM_SHUTDOWN (1 << __REQ_PM_SHUTDOWN)
#define REQ_ORDERED_COLOR (1 << __REQ_ORDERED_COLOR)
#define REQ_RW_SYNC (1 << __REQ_RW_SYNC)
/*
* State information carried for REQ_PM_SUSPEND and REQ_PM_RESUME

11
include/linux/sched.h
View file

@ -941,12 +941,11 @@ static inline void put_task_struct(struct task_struct *t)
#define PF_KSWAPD 0x00040000 /* I am kswapd */
#define PF_SWAPOFF 0x00080000 /* I am in swapoff */
#define PF_LESS_THROTTLE 0x00100000 /* Throttle me less: I clean memory */
#define PF_SYNCWRITE 0x00200000 /* I am doing a sync write */
#define PF_BORROWED_MM 0x00400000 /* I am a kthread doing use_mm */
#define PF_RANDOMIZE 0x00800000 /* randomize virtual address space */
#define PF_SWAPWRITE 0x01000000 /* Allowed to write to swap */
#define PF_SPREAD_PAGE 0x04000000 /* Spread page cache over cpuset */
#define PF_SPREAD_SLAB 0x08000000 /* Spread some slab caches over cpuset */
#define PF_BORROWED_MM 0x00200000 /* I am a kthread doing use_mm */
#define PF_RANDOMIZE 0x00400000 /* randomize virtual address space */
#define PF_SWAPWRITE 0x00800000 /* Allowed to write to swap */
#define PF_SPREAD_PAGE 0x01000000 /* Spread page cache over cpuset */
#define PF_SPREAD_SLAB 0x02000000 /* Spread some slab caches over cpuset */
#define PF_MEMPOLICY 0x10000000 /* Non-default NUMA mempolicy */
/*

3
mm/msync.c
View file

@ -170,8 +170,6 @@ asmlinkage long sys_msync(unsigned long start, size_t len, int flags)
* just ignore them, but return -ENOMEM at the end.
*/
down_read(&current->mm->mmap_sem);
if (flags & MS_SYNC)
current->flags |= PF_SYNCWRITE;
vma = find_vma(current->mm, start);
if (!vma) {
error = -ENOMEM;
@ -228,7 +226,6 @@ asmlinkage long sys_msync(unsigned long start, size_t len, int flags)
}
} while (vma && !done);
out_unlock:
current->flags &= ~PF_SYNCWRITE;
up_read(&current->mm->mmap_sem);
out:
return error;