From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: [PATCH] handle failures in __lock_fs Date: Thu, 10 Feb 2005 22:45:11 +0100 Message-ID: <20050210214511.GA15204@lst.de> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: dm-devel@redhat.com List-Id: dm-devel.ids I have a patch pending that allows freeze_bdev to return errors. To handle that in DM __lock_fs need to properly unwind and it's caller must not ignore the return value. Detailed changelog: - add a new member frozen_bdev to struct mapped_device to store the frozen block device instead of needing a second bdget_disk in __unlock_fs - handle the possibility of freeze_bdev returning an error - properly unwind all state in __lockfs in case of failure - check __unlock_fs return value to void because it doesn't return a useful value - use gotos to properly unwind in dm_suspend - handle __lock_fs error return - use test_and_set_bit for DMF_BLOCK_IO Question: how does dm_table_presuspend_targets need to be undone? --- 1.62/drivers/md/dm.c 2005-02-03 16:16:04 +01:00 +++ edited/drivers/md/dm.c 2005-02-10 22:45:38 +01:00 @@ -90,6 +90,7 @@ struct mapped_device { * freeze/thaw support require holding onto a super block */ struct super_block *frozen_sb; + struct block_device *frozen_bdev; }; #define MIN_IOS 256 @@ -975,44 +976,43 @@ int dm_swap_table(struct mapped_device * */ static int __lock_fs(struct mapped_device *md) { - struct block_device *bdev; + int error = -ENOMEM; if (test_and_set_bit(DMF_FS_LOCKED, &md->flags)) return 0; - bdev = bdget_disk(md->disk, 0); - if (!bdev) { - DMWARN("bdget failed in __lock_fs"); - return -ENOMEM; - } + md->frozen_bdev = bdget_disk(md->disk, 0); + if (!md->frozen_bdev) + goto out; WARN_ON(md->frozen_sb); - md->frozen_sb = freeze_bdev(bdev); + md->frozen_sb = freeze_bdev(md->frozen_bdev); + if (IS_ERR(md->frozen_sb)) { + error = PTR_ERR(md->frozen_sb); + goto out_bdput; + } + /* don't bdput right now, we don't want the bdev * to go away while it is locked. We'll bdput * in __unlock_fs */ return 0; + + out_bdput: + bdput(md->frozen_bdev); + out: + clear_bit(DMF_FS_LOCKED, &md->flags); + md->frozen_sb = NULL; + return error; } -static int __unlock_fs(struct mapped_device *md) +static void __unlock_fs(struct mapped_device *md) { - struct block_device *bdev; - - if (!test_and_clear_bit(DMF_FS_LOCKED, &md->flags)) - return 0; - - bdev = bdget_disk(md->disk, 0); - if (!bdev) { - DMWARN("bdget failed in __unlock_fs"); - return -ENOMEM; + if (test_and_clear_bit(DMF_FS_LOCKED, &md->flags)) { + thaw_bdev(md->frozen_bdev, md->frozen_sb); + bdput(md->frozen_bdev); + md->frozen_sb = NULL; } - - thaw_bdev(bdev, md->frozen_sb); - md->frozen_sb = NULL; - bdput(bdev); - bdput(bdev); - return 0; } /* @@ -1026,37 +1026,41 @@ int dm_suspend(struct mapped_device *md) { struct dm_table *map; DECLARE_WAITQUEUE(wait, current); + int error = -EINVAL; /* Flush I/O to the device. */ down_read(&md->lock); - if (test_bit(DMF_BLOCK_IO, &md->flags)) { - up_read(&md->lock); - return -EINVAL; - } + if (test_bit(DMF_BLOCK_IO, &md->flags)) + goto out_read_unlock; map = dm_get_table(md); if (map) dm_table_presuspend_targets(map); - __lock_fs(md); + + error = __lock_fs(md); + if (error) { + /* XXX(hch): no need to undo dm_table_presuspend_targets? */ + if (map) + dm_table_put(map); + goto out_read_unlock; + } up_read(&md->lock); /* - * First we set the BLOCK_IO flag so no more ios will be - * mapped. + * First we set the BLOCK_IO flag so no more ios will be mapped. + * + * If the flag is already set we know another thread is trying to + * suspend as well, so we leave the fs locked for this thread. */ + error = -EINVAL; down_write(&md->lock); - if (test_bit(DMF_BLOCK_IO, &md->flags)) { - /* - * If we get here we know another thread is - * trying to suspend as well, so we leave the fs - * locked for this thread. - */ - up_write(&md->lock); - return -EINVAL; + if (test_and_set_bit(DMF_BLOCK_IO, &md->flags)) { + if (map) + dm_table_put(map); + goto out_write_unlock; } - set_bit(DMF_BLOCK_IO, &md->flags); add_wait_queue(&md->wait, &wait); up_write(&md->lock); @@ -1084,12 +1088,9 @@ int dm_suspend(struct mapped_device *md) remove_wait_queue(&md->wait, &wait); /* were we interrupted ? */ - if (atomic_read(&md->pending)) { - __unlock_fs(md); - clear_bit(DMF_BLOCK_IO, &md->flags); - up_write(&md->lock); - return -EINTR; - } + error = -EINTR; + if (atomic_read(&md->pending)) + goto out_unfreeze; set_bit(DMF_SUSPENDED, &md->flags); @@ -1100,6 +1101,16 @@ int dm_suspend(struct mapped_device *md) up_write(&md->lock); return 0; + + out_unfreeze: + __unlock_fs(md); + clear_bit(DMF_BLOCK_IO, &md->flags); + out_write_unlock: + up_write(&md->lock); + return error; + out_read_unlock: + up_read(&md->lock); + return error; } int dm_resume(struct mapped_device *md) -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel