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bdi: reimplement bdev_inode_switch_bdi()

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A block_device may be attached to different gendisks and thus
different bdis over time.  bdev_inode_switch_bdi() is used to switch
the associated bdi.  The function assumes that the inode could be
dirty and transfers it between bdis if so.  This is a bit nasty in
that it reaches into bdi internals.

This patch reimplements the function so that it writes out the inode
if dirty.  This is a lot simpler and can be implemented without
exposing bdi internals.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Tejun Heo 2014-09-08 08:04:01 +09:00 • committed by Jens Axboe
parent 1a1e4530ea
commit 018a17bdc8
3 changed files with 12 additions and 23 deletions
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32
fs/block_dev.c
View file

@ -50,32 +50,22 @@ inline struct block_device *I_BDEV(struct inode *inode)
EXPORT_SYMBOL(I_BDEV); EXPORT_SYMBOL(I_BDEV);
/* /*
* Move the inode from its current bdi to a new bdi. If the inode is dirty we * Move the inode from its current bdi to a new bdi. Make sure the inode
* need to move it onto the dirty list of @dst so that the inode is always on * is clean before moving so that it doesn't linger on the old bdi.
* the right list.
*/ */
static void bdev_inode_switch_bdi(struct inode *inode, static void bdev_inode_switch_bdi(struct inode *inode,
struct backing_dev_info *dst) struct backing_dev_info *dst)
{ {
struct backing_dev_info *old = inode->i_data.backing_dev_info; while (true) {
bool wakeup_bdi = false; spin_lock(&inode->i_lock);
if (!(inode->i_state & I_DIRTY)) {
if (unlikely(dst == old)) /* deadlock avoidance */ inode->i_data.backing_dev_info = dst;
return; spin_unlock(&inode->i_lock);
bdi_lock_two(&old->wb, &dst->wb); return;
spin_lock(&inode->i_lock); }
inode->i_data.backing_dev_info = dst; spin_unlock(&inode->i_lock);
if (inode->i_state & I_DIRTY) { WARN_ON_ONCE(write_inode_now(inode, true));
if (bdi_cap_writeback_dirty(dst) && !wb_has_dirty_io(&dst->wb))
wakeup_bdi = true;
list_move(&inode->i_wb_list, &dst->wb.b_dirty);
} }
spin_unlock(&inode->i_lock);
spin_unlock(&old->wb.list_lock);
spin_unlock(&dst->wb.list_lock);
if (wakeup_bdi)
bdi_wakeup_thread_delayed(dst);
} }
/* Kill _all_ buffers and pagecache , dirty or not.. */ /* Kill _all_ buffers and pagecache , dirty or not.. */

1
include/linux/backing-dev.h
View file

@ -121,7 +121,6 @@ void bdi_start_background_writeback(struct backing_dev_info *bdi);
void bdi_writeback_workfn(struct work_struct *work); void bdi_writeback_workfn(struct work_struct *work);
int bdi_has_dirty_io(struct backing_dev_info *bdi); int bdi_has_dirty_io(struct backing_dev_info *bdi);
void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi); void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi);
void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2);
extern spinlock_t bdi_lock; extern spinlock_t bdi_lock;
extern struct list_head bdi_list; extern struct list_head bdi_list;

2
mm/backing-dev.c
View file

@ -40,7 +40,7 @@ LIST_HEAD(bdi_list);
/* bdi_wq serves all asynchronous writeback tasks */ /* bdi_wq serves all asynchronous writeback tasks */
struct workqueue_struct *bdi_wq; struct workqueue_struct *bdi_wq;
void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2) static void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2)
{ {
if (wb1 < wb2) { if (wb1 < wb2) {
spin_lock(&wb1->list_lock); spin_lock(&wb1->list_lock);