From 7f0e7bed936a0c422641a046551829a01341dd80 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 8 Jun 2010 18:14:34 +0200 Subject: writeback: fix writeback completion notifications The code dealing with bdi_work->state and completion of a bdi_work is a major mess currently. This patch makes sure we directly use one set of flags to deal with it, and use it consistently, which means: - always notify about completion from the rcu callback. We only ever wait for it from on-stack callers, so this simplification does not even cause a theoretical slowdown currently. It also makes sure we don't miss out on the notification if we ever add other callers to wait for it. - make earlier completion notification depending on the on-stack allocation, not the sync mode. If we introduce new callers that want to do WB_SYNC_NONE writeback from on-stack callers this will be nessecary. Also rename bdi_wait_on_work_clear to bdi_wait_on_work_done and inline a few small functions into their only caller to make the code understandable. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- fs/fs-writeback.c | 65 +++++++++++++------------------------------------------ 1 file changed, 15 insertions(+), 50 deletions(-) (limited to 'fs') diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 1d1088f48bc2..dbf6f108e868 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -63,24 +63,16 @@ struct bdi_work { }; enum { - WS_USED_B = 0, - WS_ONSTACK_B, + WS_INPROGRESS = 0, + WS_ONSTACK, }; -#define WS_USED (1 << WS_USED_B) -#define WS_ONSTACK (1 << WS_ONSTACK_B) - -static inline bool bdi_work_on_stack(struct bdi_work *work) -{ - return test_bit(WS_ONSTACK_B, &work->state); -} - static inline void bdi_work_init(struct bdi_work *work, struct wb_writeback_args *args) { INIT_RCU_HEAD(&work->rcu_head); work->args = *args; - work->state = WS_USED; + __set_bit(WS_INPROGRESS, &work->state); } /** @@ -95,43 +87,16 @@ int writeback_in_progress(struct backing_dev_info *bdi) return !list_empty(&bdi->work_list); } -static void bdi_work_clear(struct bdi_work *work) -{ - clear_bit(WS_USED_B, &work->state); - smp_mb__after_clear_bit(); - /* - * work can have disappeared at this point. bit waitq functions - * should be able to tolerate this, provided bdi_sched_wait does - * not dereference it's pointer argument. - */ - wake_up_bit(&work->state, WS_USED_B); -} - static void bdi_work_free(struct rcu_head *head) { struct bdi_work *work = container_of(head, struct bdi_work, rcu_head); - if (!bdi_work_on_stack(work)) - kfree(work); - else - bdi_work_clear(work); -} - -static void wb_work_complete(struct bdi_work *work) -{ - const enum writeback_sync_modes sync_mode = work->args.sync_mode; - int onstack = bdi_work_on_stack(work); + clear_bit(WS_INPROGRESS, &work->state); + smp_mb__after_clear_bit(); + wake_up_bit(&work->state, WS_INPROGRESS); - /* - * For allocated work, we can clear the done/seen bit right here. - * For on-stack work, we need to postpone both the clear and free - * to after the RCU grace period, since the stack could be invalidated - * as soon as bdi_work_clear() has done the wakeup. - */ - if (!onstack) - bdi_work_clear(work); - if (sync_mode == WB_SYNC_NONE || onstack) - call_rcu(&work->rcu_head, bdi_work_free); + if (!test_bit(WS_ONSTACK, &work->state)) + kfree(work); } static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *work) @@ -147,7 +112,7 @@ static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *work) list_del_rcu(&work->list); spin_unlock(&bdi->wb_lock); - wb_work_complete(work); + call_rcu(&work->rcu_head, bdi_work_free); } } @@ -185,9 +150,9 @@ static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work) * Used for on-stack allocated work items. The caller needs to wait until * the wb threads have acked the work before it's safe to continue. */ -static void bdi_wait_on_work_clear(struct bdi_work *work) +static void bdi_wait_on_work_done(struct bdi_work *work) { - wait_on_bit(&work->state, WS_USED_B, bdi_sched_wait, + wait_on_bit(&work->state, WS_INPROGRESS, bdi_sched_wait, TASK_UNINTERRUPTIBLE); } @@ -234,10 +199,10 @@ static void bdi_sync_writeback(struct backing_dev_info *bdi, struct bdi_work work; bdi_work_init(&work, &args); - work.state |= WS_ONSTACK; + __set_bit(WS_ONSTACK, &work.state); bdi_queue_work(bdi, &work); - bdi_wait_on_work_clear(&work); + bdi_wait_on_work_done(&work); } /** @@ -911,7 +876,7 @@ long wb_do_writeback(struct bdi_writeback *wb, int force_wait) * If this isn't a data integrity operation, just notify * that we have seen this work and we are now starting it. */ - if (args.sync_mode == WB_SYNC_NONE) + if (!test_bit(WS_ONSTACK, &work->state)) wb_clear_pending(wb, work); wrote += wb_writeback(wb, &args); @@ -920,7 +885,7 @@ long wb_do_writeback(struct bdi_writeback *wb, int force_wait) * This is a data integrity writeback, so only do the * notification when we have completed the work. */ - if (args.sync_mode == WB_SYNC_ALL) + if (test_bit(WS_ONSTACK, &work->state)) wb_clear_pending(wb, work); } -- cgit v1.2.3 From 3c4d716538f3eefb1c1f10961a047a6456a2b590 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 8 Jun 2010 18:14:43 +0200 Subject: writeback: queue work on stack in writeback_inodes_sb If we want to rely on s_umount in the caller we need to wait for completion of the I/O submission before returning to the caller. Refactor bdi_sync_writeback into a bdi_queue_work_onstack helper and use it for this case. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- fs/fs-writeback.c | 40 +++++++++++++++++++++------------------- 1 file changed, 21 insertions(+), 19 deletions(-) (limited to 'fs') diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index dbf6f108e868..759666966c6d 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -178,30 +178,22 @@ static void bdi_alloc_queue_work(struct backing_dev_info *bdi, } /** - * bdi_sync_writeback - start and wait for writeback - * @bdi: the backing device to write from + * bdi_queue_work_onstack - start and wait for writeback * @sb: write inodes from this super_block * * Description: - * This does WB_SYNC_ALL data integrity writeback and waits for the - * IO to complete. Callers must hold the sb s_umount semaphore for + * This function initiates writeback and waits for the operation to + * complete. Callers must hold the sb s_umount semaphore for * reading, to avoid having the super disappear before we are done. */ -static void bdi_sync_writeback(struct backing_dev_info *bdi, - struct super_block *sb) +static void bdi_queue_work_onstack(struct wb_writeback_args *args) { - struct wb_writeback_args args = { - .sb = sb, - .sync_mode = WB_SYNC_ALL, - .nr_pages = LONG_MAX, - .range_cyclic = 0, - }; struct bdi_work work; - bdi_work_init(&work, &args); + bdi_work_init(&work, args); __set_bit(WS_ONSTACK, &work.state); - bdi_queue_work(bdi, &work); + bdi_queue_work(args->sb->s_bdi, &work); bdi_wait_on_work_done(&work); } @@ -944,7 +936,7 @@ int bdi_writeback_task(struct bdi_writeback *wb) /* * Schedule writeback for all backing devices. This does WB_SYNC_NONE - * writeback, for integrity writeback see bdi_sync_writeback(). + * writeback, for integrity writeback see bdi_queue_work_onstack(). */ static void bdi_writeback_all(struct super_block *sb, long nr_pages) { @@ -1183,12 +1175,15 @@ void writeback_inodes_sb(struct super_block *sb) { unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY); unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS); - long nr_to_write; + struct wb_writeback_args args = { + .sb = sb, + .sync_mode = WB_SYNC_NONE, + }; - nr_to_write = nr_dirty + nr_unstable + + args.nr_pages = nr_dirty + nr_unstable + (inodes_stat.nr_inodes - inodes_stat.nr_unused); - bdi_start_writeback(sb->s_bdi, sb, nr_to_write); + bdi_queue_work_onstack(&args); } EXPORT_SYMBOL(writeback_inodes_sb); @@ -1218,7 +1213,14 @@ EXPORT_SYMBOL(writeback_inodes_sb_if_idle); */ void sync_inodes_sb(struct super_block *sb) { - bdi_sync_writeback(sb->s_bdi, sb); + struct wb_writeback_args args = { + .sb = sb, + .sync_mode = WB_SYNC_ALL, + .nr_pages = LONG_MAX, + .range_cyclic = 0, + }; + + bdi_queue_work_onstack(&args); wait_sb_inodes(sb); } EXPORT_SYMBOL(sync_inodes_sb); -- cgit v1.2.3 From cf37e972478ec58a8a54a6b4f951815f0ae28f78 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 8 Jun 2010 18:14:51 +0200 Subject: writeback: enforce s_umount locking in writeback_inodes_sb Make sure that not only sync_filesystem but all callers of writeback_inodes_sb have the superblock protected against remount. As-is this disables all functionality for these callers, but the next patch relies on this locking to fix writeback_inodes_sb for sync_filesystem. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- fs/fs-writeback.c | 6 ++++++ fs/ubifs/budget.c | 2 ++ 2 files changed, 8 insertions(+) (limited to 'fs') diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 759666966c6d..2627f0dfcd9c 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -1180,6 +1180,8 @@ void writeback_inodes_sb(struct super_block *sb) .sync_mode = WB_SYNC_NONE, }; + WARN_ON(!rwsem_is_locked(&sb->s_umount)); + args.nr_pages = nr_dirty + nr_unstable + (inodes_stat.nr_inodes - inodes_stat.nr_unused); @@ -1197,7 +1199,9 @@ EXPORT_SYMBOL(writeback_inodes_sb); int writeback_inodes_sb_if_idle(struct super_block *sb) { if (!writeback_in_progress(sb->s_bdi)) { + down_read(&sb->s_umount); writeback_inodes_sb(sb); + up_read(&sb->s_umount); return 1; } else return 0; @@ -1220,6 +1224,8 @@ void sync_inodes_sb(struct super_block *sb) .range_cyclic = 0, }; + WARN_ON(!rwsem_is_locked(&sb->s_umount)); + bdi_queue_work_onstack(&args); wait_sb_inodes(sb); } diff --git a/fs/ubifs/budget.c b/fs/ubifs/budget.c index 076ca50e9933..c8ff0d1ae5d3 100644 --- a/fs/ubifs/budget.c +++ b/fs/ubifs/budget.c @@ -62,7 +62,9 @@ */ static void shrink_liability(struct ubifs_info *c, int nr_to_write) { + down_read(&c->vfs_sb->s_umount); writeback_inodes_sb(c->vfs_sb); + up_read(&c->vfs_sb->s_umount); } /** -- cgit v1.2.3 From d19de7edf59cdd586777b009e0e8fbe5412dd35f Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 8 Jun 2010 18:14:58 +0200 Subject: writeback: fix writeback_inodes_wb from writeback_inodes_sb When we call writeback_inodes_wb from writeback_inodes_sb we always have s_umount held, which currently makes the whole operation a no-op. But if we are called to write out inodes for a specific superblock we always have s_umount held, so replace the incorrect logic checking for WB_SYNC_ALL which only worked by coincidence with the proper check for an explicit superblock argument. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- fs/fs-writeback.c | 61 +++++++++++++++++++++---------------------------------- 1 file changed, 23 insertions(+), 38 deletions(-) (limited to 'fs') diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 2627f0dfcd9c..68ece4b18916 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -518,39 +518,19 @@ select_queue: return ret; } -static void unpin_sb_for_writeback(struct super_block *sb) -{ - up_read(&sb->s_umount); - put_super(sb); -} - -enum sb_pin_state { - SB_PINNED, - SB_NOT_PINNED, - SB_PIN_FAILED -}; - /* - * For WB_SYNC_NONE writeback, the caller does not have the sb pinned + * For background writeback the caller does not have the sb pinned * before calling writeback. So make sure that we do pin it, so it doesn't * go away while we are writing inodes from it. */ -static enum sb_pin_state pin_sb_for_writeback(struct writeback_control *wbc, - struct super_block *sb) +static bool pin_sb_for_writeback(struct super_block *sb) { - /* - * Caller must already hold the ref for this - */ - if (wbc->sync_mode == WB_SYNC_ALL) { - WARN_ON(!rwsem_is_locked(&sb->s_umount)); - return SB_NOT_PINNED; - } spin_lock(&sb_lock); sb->s_count++; if (down_read_trylock(&sb->s_umount)) { if (sb->s_root) { spin_unlock(&sb_lock); - return SB_PINNED; + return true; } /* * umounted, drop rwsem again and fall through to failure @@ -559,7 +539,7 @@ static enum sb_pin_state pin_sb_for_writeback(struct writeback_control *wbc, } sb->s_count--; spin_unlock(&sb_lock); - return SB_PIN_FAILED; + return false; } /* @@ -638,24 +618,29 @@ static void writeback_inodes_wb(struct bdi_writeback *wb, struct inode *inode = list_entry(wb->b_io.prev, struct inode, i_list); struct super_block *sb = inode->i_sb; - enum sb_pin_state state; - if (wbc->sb && sb != wbc->sb) { - /* super block given and doesn't - match, skip this inode */ - redirty_tail(inode); - continue; - } - state = pin_sb_for_writeback(wbc, sb); + if (wbc->sb) { + /* + * We are requested to write out inodes for a specific + * superblock. This means we already have s_umount + * taken by the caller which also waits for us to + * complete the writeout. + */ + if (sb != wbc->sb) { + redirty_tail(inode); + continue; + } - if (state == SB_PIN_FAILED) { - requeue_io(inode); - continue; + WARN_ON(!rwsem_is_locked(&sb->s_umount)); + + ret = writeback_sb_inodes(sb, wb, wbc); + } else { + if (!pin_sb_for_writeback(sb)) + continue; + ret = writeback_sb_inodes(sb, wb, wbc); + drop_super(sb); } - ret = writeback_sb_inodes(sb, wb, wbc); - if (state == SB_PINNED) - unpin_sb_for_writeback(sb); if (ret) break; } -- cgit v1.2.3 From b8c2f3474f1077599ec6e90c2f263f17055cc3d8 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 8 Jun 2010 18:15:07 +0200 Subject: writeback: simplify wakeup_flusher_threads bdi_writeback_all only has one caller, so fold it to simplify the code and flatten the call stack. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- fs/fs-writeback.c | 32 +++++++++++--------------------- 1 file changed, 11 insertions(+), 21 deletions(-) (limited to 'fs') diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 68ece4b18916..4fcca4f74940 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -920,42 +920,32 @@ int bdi_writeback_task(struct bdi_writeback *wb) } /* - * Schedule writeback for all backing devices. This does WB_SYNC_NONE - * writeback, for integrity writeback see bdi_queue_work_onstack(). + * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back + * the whole world. */ -static void bdi_writeback_all(struct super_block *sb, long nr_pages) +void wakeup_flusher_threads(long nr_pages) { + struct backing_dev_info *bdi; struct wb_writeback_args args = { - .sb = sb, - .nr_pages = nr_pages, .sync_mode = WB_SYNC_NONE, }; - struct backing_dev_info *bdi; - rcu_read_lock(); + if (nr_pages) { + args.nr_pages = nr_pages; + } else { + args.nr_pages = global_page_state(NR_FILE_DIRTY) + + global_page_state(NR_UNSTABLE_NFS); + } + rcu_read_lock(); list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) { if (!bdi_has_dirty_io(bdi)) continue; - bdi_alloc_queue_work(bdi, &args); } - rcu_read_unlock(); } -/* - * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back - * the whole world. - */ -void wakeup_flusher_threads(long nr_pages) -{ - if (nr_pages == 0) - nr_pages = global_page_state(NR_FILE_DIRTY) + - global_page_state(NR_UNSTABLE_NFS); - bdi_writeback_all(NULL, nr_pages); -} - static noinline void block_dump___mark_inode_dirty(struct inode *inode) { if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) { -- cgit v1.2.3 From c5444198ca210498e8ac0ba121b4cd3537aa12f7 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 8 Jun 2010 18:15:15 +0200 Subject: writeback: simplify and split bdi_start_writeback bdi_start_writeback now never gets a superblock passed, so we can just remove that case. And to further untangle the code and flatten the call stack split it into two trivial helpers for it's two callers. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- fs/fs-writeback.c | 32 ++++++++++++++++++++------------ include/linux/backing-dev.h | 4 ++-- mm/page-writeback.c | 5 ++--- 3 files changed, 24 insertions(+), 17 deletions(-) (limited to 'fs') diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 4fcca4f74940..0079bf59b583 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -200,7 +200,6 @@ static void bdi_queue_work_onstack(struct wb_writeback_args *args) /** * bdi_start_writeback - start writeback * @bdi: the backing device to write from - * @sb: write inodes from this super_block * @nr_pages: the number of pages to write * * Description: @@ -209,25 +208,34 @@ static void bdi_queue_work_onstack(struct wb_writeback_args *args) * completion. Caller need not hold sb s_umount semaphore. * */ -void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb, - long nr_pages) +void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages) { struct wb_writeback_args args = { - .sb = sb, .sync_mode = WB_SYNC_NONE, .nr_pages = 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); +} +/** + * bdi_start_background_writeback - start background writeback + * @bdi: the backing device to write from + * + * Description: + * This does WB_SYNC_NONE background writeback. The IO is only + * started when this function returns, we make no guarentees on + * completion. Caller need not hold sb s_umount semaphore. + */ +void bdi_start_background_writeback(struct backing_dev_info *bdi) +{ + struct wb_writeback_args args = { + .sync_mode = WB_SYNC_NONE, + .nr_pages = LONG_MAX, + .for_background = 1, + .range_cyclic = 1, + }; bdi_alloc_queue_work(bdi, &args); } diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h index aee5f6ce166e..9ae2889096b6 100644 --- a/include/linux/backing-dev.h +++ b/include/linux/backing-dev.h @@ -105,8 +105,8 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent, int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev); void bdi_unregister(struct backing_dev_info *bdi); int bdi_setup_and_register(struct backing_dev_info *, char *, unsigned int); -void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb, - long nr_pages); +void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages); +void bdi_start_background_writeback(struct backing_dev_info *bdi); int bdi_writeback_task(struct bdi_writeback *wb); int bdi_has_dirty_io(struct backing_dev_info *bdi); void bdi_arm_supers_timer(void); diff --git a/mm/page-writeback.c b/mm/page-writeback.c index bbd396ac9546..54f28bd493d3 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -597,7 +597,7 @@ static void balance_dirty_pages(struct address_space *mapping, (!laptop_mode && ((global_page_state(NR_FILE_DIRTY) + global_page_state(NR_UNSTABLE_NFS)) > background_thresh))) - bdi_start_writeback(bdi, NULL, 0); + bdi_start_background_writeback(bdi); } void set_page_dirty_balance(struct page *page, int page_mkwrite) @@ -705,9 +705,8 @@ void laptop_mode_timer_fn(unsigned long data) * We want to write everything out, not just down to the dirty * threshold */ - if (bdi_has_dirty_io(&q->backing_dev_info)) - bdi_start_writeback(&q->backing_dev_info, NULL, nr_pages); + bdi_start_writeback(&q->backing_dev_info, nr_pages); } /* -- cgit v1.2.3 From 334132ae921a14ac2b2ba48e174136f7f2c9aae1 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 9 Jun 2010 14:28:43 +0200 Subject: writeback: add missing requeue_io in writeback_inodes_wb In "writeback: fix writeback_inodes_wb from writeback_inodes_sb" I accidentally removed the requeue_io if we need to skip a superblock because we can't pin it. Add it back, otherwise we're getting spurious lockups after multiple xfstests runs. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- fs/fs-writeback.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'fs') diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 0079bf59b583..3a066e91ec8d 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -643,8 +643,10 @@ static void writeback_inodes_wb(struct bdi_writeback *wb, ret = writeback_sb_inodes(sb, wb, wbc); } else { - if (!pin_sb_for_writeback(sb)) + if (!pin_sb_for_writeback(sb)) { + requeue_io(inode); continue; + } ret = writeback_sb_inodes(sb, wb, wbc); drop_super(sb); } -- cgit v1.2.3 From 29cb48594b873f6193d6327097e504bd3e2314de Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 9 Jun 2010 15:31:01 +0200 Subject: writeback: fix pin_sb_for_writeback We need to check for s_instances to make sure we don't bother working against a filesystem that is beeing unmounted, and we need to call put_super to make sure a superblock is freed when we race against umount. Also no need to keep sb_lock after we got a reference on it. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- fs/fs-writeback.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) (limited to 'fs') diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 3a066e91ec8d..0609607d3955 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -534,19 +534,21 @@ select_queue: static bool pin_sb_for_writeback(struct super_block *sb) { spin_lock(&sb_lock); + if (list_empty(&sb->s_instances)) { + spin_unlock(&sb_lock); + return false; + } + sb->s_count++; + spin_unlock(&sb_lock); + if (down_read_trylock(&sb->s_umount)) { - if (sb->s_root) { - spin_unlock(&sb_lock); + if (sb->s_root) return true; - } - /* - * umounted, drop rwsem again and fall through to failure - */ up_read(&sb->s_umount); } - sb->s_count--; - spin_unlock(&sb_lock); + + put_super(sb); return false; } -- cgit v1.2.3