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Merge branch 'writeback' of git://git.kernel.dk/linux-2.6-block
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* 'writeback' of git://git.kernel.dk/linux-2.6-block:
  writeback: writeback_inodes_sb() should use bdi_start_writeback()
  writeback: don't delay inodes redirtied by a fast dirtier
  writeback: make the super_block pinning more efficient
  writeback: don't resort for a single super_block in move_expired_inodes()
  writeback: move inodes from one super_block together
  writeback: get rid to incorrect references to pdflush in comments
  writeback: improve readability of the wb_writeback() continue/break logic
  writeback: cleanup writeback_single_inode()
  writeback: kupdate writeback shall not stop when more io is possible
  writeback: stop background writeback when below background threshold
  writeback: balance_dirty_pages() shall write more than dirtied pages
  fs: Fix busyloop in wb_writeback()
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Linus Torvalds committed Sep 25, 2009
2 parents 53cddfc + 56a131d commit 6d7f18f
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Showing 5 changed files with 142 additions and 72 deletions.
10 changes: 5 additions & 5 deletions fs/buffer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -280,7 +280,7 @@ void invalidate_bdev(struct block_device *bdev)
EXPORT_SYMBOL(invalidate_bdev);

/*
* Kick pdflush then try to free up some ZONE_NORMAL memory.
* Kick the writeback threads then try to free up some ZONE_NORMAL memory.
*/
static void free_more_memory(void)
{
Expand Down Expand Up @@ -1709,9 +1709,9 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
/*
* If it's a fully non-blocking write attempt and we cannot
* lock the buffer then redirty the page. Note that this can
* potentially cause a busy-wait loop from pdflush and kswapd
* activity, but those code paths have their own higher-level
* throttling.
* potentially cause a busy-wait loop from writeback threads
* and kswapd activity, but those code paths have their own
* higher-level throttling.
*/
if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
lock_buffer(bh);
Expand Down Expand Up @@ -3208,7 +3208,7 @@ EXPORT_SYMBOL(block_sync_page);
* still running obsolete flush daemons, so we terminate them here.
*
* Use of bdflush() is deprecated and will be removed in a future kernel.
* The `pdflush' kernel threads fully replace bdflush daemons and this call.
* The `flush-X' kernel threads fully replace bdflush daemons and this call.
*/
SYSCALL_DEFINE2(bdflush, int, func, long, data)
{
Expand Down
161 changes: 113 additions & 48 deletions fs/fs-writeback.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -41,8 +41,9 @@ struct wb_writeback_args {
long nr_pages;
struct super_block *sb;
enum writeback_sync_modes sync_mode;
int for_kupdate;
int range_cyclic;
int for_kupdate:1;
int range_cyclic:1;
int for_background:1;
};

/*
Expand Down Expand Up @@ -257,6 +258,15 @@ void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages)
.range_cyclic = 1,
};

/*
* We treat @nr_pages=0 as the special case to do background writeback,
* ie. to sync pages until the background dirty threshold is reached.
*/
if (!nr_pages) {
args.nr_pages = LONG_MAX;
args.for_background = 1;
}

bdi_alloc_queue_work(bdi, &args);
}

Expand Down Expand Up @@ -310,7 +320,7 @@ static bool inode_dirtied_after(struct inode *inode, unsigned long t)
* For inodes being constantly redirtied, dirtied_when can get stuck.
* It _appears_ to be in the future, but is actually in distant past.
* This test is necessary to prevent such wrapped-around relative times
* from permanently stopping the whole pdflush writeback.
* from permanently stopping the whole bdi writeback.
*/
ret = ret && time_before_eq(inode->dirtied_when, jiffies);
#endif
Expand All @@ -324,13 +334,38 @@ static void move_expired_inodes(struct list_head *delaying_queue,
struct list_head *dispatch_queue,
unsigned long *older_than_this)
{
LIST_HEAD(tmp);
struct list_head *pos, *node;
struct super_block *sb = NULL;
struct inode *inode;
int do_sb_sort = 0;

while (!list_empty(delaying_queue)) {
struct inode *inode = list_entry(delaying_queue->prev,
struct inode, i_list);
inode = list_entry(delaying_queue->prev, struct inode, i_list);
if (older_than_this &&
inode_dirtied_after(inode, *older_than_this))
break;
list_move(&inode->i_list, dispatch_queue);
if (sb && sb != inode->i_sb)
do_sb_sort = 1;
sb = inode->i_sb;
list_move(&inode->i_list, &tmp);
}

/* just one sb in list, splice to dispatch_queue and we're done */
if (!do_sb_sort) {
list_splice(&tmp, dispatch_queue);
return;
}

/* Move inodes from one superblock together */
while (!list_empty(&tmp)) {
inode = list_entry(tmp.prev, struct inode, i_list);
sb = inode->i_sb;
list_for_each_prev_safe(pos, node, &tmp) {
inode = list_entry(pos, struct inode, i_list);
if (inode->i_sb == sb)
list_move(&inode->i_list, dispatch_queue);
}
}
}

Expand Down Expand Up @@ -439,8 +474,18 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
spin_lock(&inode_lock);
inode->i_state &= ~I_SYNC;
if (!(inode->i_state & (I_FREEING | I_CLEAR))) {
if (!(inode->i_state & I_DIRTY) &&
mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
if ((inode->i_state & I_DIRTY_PAGES) && wbc->for_kupdate) {
/*
* More pages get dirtied by a fast dirtier.
*/
goto select_queue;
} else if (inode->i_state & I_DIRTY) {
/*
* At least XFS will redirty the inode during the
* writeback (delalloc) and on io completion (isize).
*/
redirty_tail(inode);
} else if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
/*
* We didn't write back all the pages. nfs_writepages()
* sometimes bales out without doing anything. Redirty
Expand All @@ -462,6 +507,7 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
* soon as the queue becomes uncongested.
*/
inode->i_state |= I_DIRTY_PAGES;
select_queue:
if (wbc->nr_to_write <= 0) {
/*
* slice used up: queue for next turn
Expand All @@ -484,12 +530,6 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
inode->i_state |= I_DIRTY_PAGES;
redirty_tail(inode);
}
} else if (inode->i_state & I_DIRTY) {
/*
* Someone redirtied the inode while were writing back
* the pages.
*/
redirty_tail(inode);
} else if (atomic_read(&inode->i_count)) {
/*
* The inode is clean, inuse
Expand All @@ -506,6 +546,17 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
return ret;
}

static void unpin_sb_for_writeback(struct super_block **psb)
{
struct super_block *sb = *psb;

if (sb) {
up_read(&sb->s_umount);
put_super(sb);
*psb = NULL;
}
}

/*
* For WB_SYNC_NONE writeback, the caller does not have the sb pinned
* before calling writeback. So make sure that we do pin it, so it doesn't
Expand All @@ -515,10 +566,19 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
* 1 if we failed.
*/
static int pin_sb_for_writeback(struct writeback_control *wbc,
struct inode *inode)
struct inode *inode, struct super_block **psb)
{
struct super_block *sb = inode->i_sb;

/*
* If this sb is already pinned, nothing more to do. If not and
* *psb is non-NULL, unpin the old one first
*/
if (sb == *psb)
return 0;
else if (*psb)
unpin_sb_for_writeback(psb);

/*
* Caller must already hold the ref for this
*/
Expand All @@ -532,7 +592,7 @@ static int pin_sb_for_writeback(struct writeback_control *wbc,
if (down_read_trylock(&sb->s_umount)) {
if (sb->s_root) {
spin_unlock(&sb_lock);
return 0;
goto pinned;
}
/*
* umounted, drop rwsem again and fall through to failure
Expand All @@ -543,24 +603,15 @@ static int pin_sb_for_writeback(struct writeback_control *wbc,
sb->s_count--;
spin_unlock(&sb_lock);
return 1;
}

static void unpin_sb_for_writeback(struct writeback_control *wbc,
struct inode *inode)
{
struct super_block *sb = inode->i_sb;

if (wbc->sync_mode == WB_SYNC_ALL)
return;

up_read(&sb->s_umount);
put_super(sb);
pinned:
*psb = sb;
return 0;
}

static void writeback_inodes_wb(struct bdi_writeback *wb,
struct writeback_control *wbc)
{
struct super_block *sb = wbc->sb;
struct super_block *sb = wbc->sb, *pin_sb = NULL;
const int is_blkdev_sb = sb_is_blkdev_sb(sb);
const unsigned long start = jiffies; /* livelock avoidance */

Expand Down Expand Up @@ -619,7 +670,7 @@ static void writeback_inodes_wb(struct bdi_writeback *wb,
if (inode_dirtied_after(inode, start))
break;

if (pin_sb_for_writeback(wbc, inode)) {
if (pin_sb_for_writeback(wbc, inode, &pin_sb)) {
requeue_io(inode);
continue;
}
Expand All @@ -628,7 +679,6 @@ static void writeback_inodes_wb(struct bdi_writeback *wb,
__iget(inode);
pages_skipped = wbc->pages_skipped;
writeback_single_inode(inode, wbc);
unpin_sb_for_writeback(wbc, inode);
if (wbc->pages_skipped != pages_skipped) {
/*
* writeback is not making progress due to locked
Expand All @@ -648,6 +698,8 @@ static void writeback_inodes_wb(struct bdi_writeback *wb,
wbc->more_io = 1;
}

unpin_sb_for_writeback(&pin_sb);

spin_unlock(&inode_lock);
/* Leave any unwritten inodes on b_io */
}
Expand Down Expand Up @@ -706,6 +758,7 @@ static long wb_writeback(struct bdi_writeback *wb,
};
unsigned long oldest_jif;
long wrote = 0;
struct inode *inode;

if (wbc.for_kupdate) {
wbc.older_than_this = &oldest_jif;
Expand All @@ -719,20 +772,16 @@ static long wb_writeback(struct bdi_writeback *wb,

for (;;) {
/*
* Don't flush anything for non-integrity writeback where
* no nr_pages was given
* Stop writeback when nr_pages has been consumed
*/
if (!args->for_kupdate && args->nr_pages <= 0 &&
args->sync_mode == WB_SYNC_NONE)
if (args->nr_pages <= 0)
break;

/*
* If no specific pages were given and this is just a
* periodic background writeout and we are below the
* background dirty threshold, don't do anything
* For background writeout, stop when we are below the
* background dirty threshold
*/
if (args->for_kupdate && args->nr_pages <= 0 &&
!over_bground_thresh())
if (args->for_background && !over_bground_thresh())
break;

wbc.more_io = 0;
Expand All @@ -744,13 +793,32 @@ static long wb_writeback(struct bdi_writeback *wb,
wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write;

/*
* If we ran out of stuff to write, bail unless more_io got set
* If we consumed everything, see if we have more
*/
if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) {
if (wbc.more_io && !wbc.for_kupdate)
continue;
if (wbc.nr_to_write <= 0)
continue;
/*
* Didn't write everything and we don't have more IO, bail
*/
if (!wbc.more_io)
break;
/*
* Did we write something? Try for more
*/
if (wbc.nr_to_write < MAX_WRITEBACK_PAGES)
continue;
/*
* Nothing written. Wait for some inode to
* become available for writeback. Otherwise
* we'll just busyloop.
*/
spin_lock(&inode_lock);
if (!list_empty(&wb->b_more_io)) {
inode = list_entry(wb->b_more_io.prev,
struct inode, i_list);
inode_wait_for_writeback(inode);
}
spin_unlock(&inode_lock);
}

return wrote;
Expand Down Expand Up @@ -1060,9 +1128,6 @@ EXPORT_SYMBOL(__mark_inode_dirty);
* If older_than_this is non-NULL, then only write out inodes which
* had their first dirtying at a time earlier than *older_than_this.
*
* If we're a pdlfush thread, then implement pdflush collision avoidance
* against the entire list.
*
* If `bdi' is non-zero then we're being asked to writeback a specific queue.
* This function assumes that the blockdev superblock's inodes are backed by
* a variety of queues, so all inodes are searched. For other superblocks,
Expand Down Expand Up @@ -1141,7 +1206,7 @@ void writeback_inodes_sb(struct super_block *sb)
nr_to_write = nr_dirty + nr_unstable +
(inodes_stat.nr_inodes - inodes_stat.nr_unused);

bdi_writeback_all(sb, nr_to_write);
bdi_start_writeback(sb->s_bdi, nr_to_write);
}
EXPORT_SYMBOL(writeback_inodes_sb);

Expand Down
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