From f30a7d0cc8d9096d6728fadd0ab024e648010ec0 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Fri, 22 May 2015 17:14:00 -0400 Subject: [PATCH] writeback: restructure try_writeback_inodes_sb[_nr]() try_writeback_inodes_sb_nr() wraps writeback_inodes_sb_nr() so that it handles s_umount locking and skips if writeback is already in progress. The in progress test is performed on the root wb (bdi_writeback) which isn't sufficient for cgroup writeback support. The test must be done per-wb. To prepare for the change, this patch factors out __writeback_inodes_sb_nr() from writeback_inodes_sb_nr() and adds @skip_if_busy and moves the in progress test right before queueing the wb_writeback_work. try_writeback_inodes_sb_nr() now just grabs s_umount and invokes __writeback_inodes_sb_nr() with asserted @skip_if_busy. This way, later addition of multiple wb handling can skip only the wb's which already have writeback in progress. This swaps the order between in progress test and s_umount test which can flip the return value when writeback is in progress and s_umount is being held by someone else but this shouldn't cause any meaningful difference. It's a fringe condition and the return value is an unsynchronized hint anyway. Signed-off-by: Tejun Heo Cc: Jens Axboe Cc: Jan Kara Signed-off-by: Jens Axboe --- fs/fs-writeback.c | 52 ++++++++++++++++++++++----------------- include/linux/writeback.h | 6 ++--- 2 files changed, 32 insertions(+), 26 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 093b9594e846..0039c5839cdd 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -1581,19 +1581,8 @@ static void wait_sb_inodes(struct super_block *sb) iput(old_inode); } -/** - * writeback_inodes_sb_nr - writeback dirty inodes from given super_block - * @sb: the superblock - * @nr: the number of pages to write - * @reason: reason why some writeback work initiated - * - * Start writeback on some inodes on this super_block. No guarantees are made - * on how many (if any) will be written, and this function does not wait - * for IO completion of submitted IO. - */ -void writeback_inodes_sb_nr(struct super_block *sb, - unsigned long nr, - enum wb_reason reason) +static void __writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr, + enum wb_reason reason, bool skip_if_busy) { DEFINE_WB_COMPLETION_ONSTACK(done); struct wb_writeback_work work = { @@ -1609,9 +1598,30 @@ void writeback_inodes_sb_nr(struct super_block *sb, if (!bdi_has_dirty_io(bdi) || bdi == &noop_backing_dev_info) return; WARN_ON(!rwsem_is_locked(&sb->s_umount)); + + if (skip_if_busy && writeback_in_progress(&bdi->wb)) + return; + wb_queue_work(&bdi->wb, &work); wb_wait_for_completion(bdi, &done); } + +/** + * writeback_inodes_sb_nr - writeback dirty inodes from given super_block + * @sb: the superblock + * @nr: the number of pages to write + * @reason: reason why some writeback work initiated + * + * Start writeback on some inodes on this super_block. No guarantees are made + * on how many (if any) will be written, and this function does not wait + * for IO completion of submitted IO. + */ +void writeback_inodes_sb_nr(struct super_block *sb, + unsigned long nr, + enum wb_reason reason) +{ + __writeback_inodes_sb_nr(sb, nr, reason, false); +} EXPORT_SYMBOL(writeback_inodes_sb_nr); /** @@ -1638,19 +1648,15 @@ EXPORT_SYMBOL(writeback_inodes_sb); * Invoke writeback_inodes_sb_nr if no writeback is currently underway. * Returns 1 if writeback was started, 0 if not. */ -int try_to_writeback_inodes_sb_nr(struct super_block *sb, - unsigned long nr, - enum wb_reason reason) +bool try_to_writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr, + enum wb_reason reason) { - if (writeback_in_progress(&sb->s_bdi->wb)) - return 1; - if (!down_read_trylock(&sb->s_umount)) - return 0; + return false; - writeback_inodes_sb_nr(sb, nr, reason); + __writeback_inodes_sb_nr(sb, nr, reason, true); up_read(&sb->s_umount); - return 1; + return true; } EXPORT_SYMBOL(try_to_writeback_inodes_sb_nr); @@ -1662,7 +1668,7 @@ EXPORT_SYMBOL(try_to_writeback_inodes_sb_nr); * Implement by try_to_writeback_inodes_sb_nr() * Returns 1 if writeback was started, 0 if not. */ -int try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason) +bool try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason) { return try_to_writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason); } diff --git a/include/linux/writeback.h b/include/linux/writeback.h index a6b9db7fcee8..23af355d5471 100644 --- a/include/linux/writeback.h +++ b/include/linux/writeback.h @@ -93,9 +93,9 @@ struct bdi_writeback; void writeback_inodes_sb(struct super_block *, enum wb_reason reason); void writeback_inodes_sb_nr(struct super_block *, unsigned long nr, enum wb_reason reason); -int try_to_writeback_inodes_sb(struct super_block *, enum wb_reason reason); -int try_to_writeback_inodes_sb_nr(struct super_block *, unsigned long nr, - enum wb_reason reason); +bool try_to_writeback_inodes_sb(struct super_block *, enum wb_reason reason); +bool try_to_writeback_inodes_sb_nr(struct super_block *, unsigned long nr, + enum wb_reason reason); void sync_inodes_sb(struct super_block *); void wakeup_flusher_threads(long nr_pages, enum wb_reason reason); void inode_wait_for_writeback(struct inode *inode); -- 2.20.1