From a3bdccc4e683f0ac69230707ed3fa20e7cf73a79 Mon Sep 17 00:00:00 2001 From: Chris Mason Date: Fri, 24 Apr 2015 11:00:00 -0700 Subject: [PATCH] Btrfs: prevent list corruption during free space cache processing __btrfs_write_out_cache is holding the ctl->tree_lock while it prepares a list of bitmaps to record in the free space cache. It was dropping the lock while it worked on other components, which made a window for free_bitmap() to free the bitmap struct without removing it from the list. This changes things to hold the lock the whole time, and also makes sure we hold the lock during enospc cleanup. Reported-by: Filipe Manana Signed-off-by: Chris Mason --- fs/btrfs/free-space-cache.c | 32 ++++++++++++++++++-------------- 1 file changed, 18 insertions(+), 14 deletions(-) diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c index d773f229d14d..81fa75a8e1f3 100644 --- a/fs/btrfs/free-space-cache.c +++ b/fs/btrfs/free-space-cache.c @@ -1119,10 +1119,7 @@ static int flush_dirty_cache(struct inode *inode) } static void noinline_for_stack -cleanup_write_cache_enospc(struct inode *inode, - struct btrfs_io_ctl *io_ctl, - struct extent_state **cached_state, - struct list_head *bitmap_list) +cleanup_bitmap_list(struct list_head *bitmap_list) { struct list_head *pos, *n; @@ -1131,6 +1128,14 @@ cleanup_write_cache_enospc(struct inode *inode, list_entry(pos, struct btrfs_free_space, list); list_del_init(&entry->list); } +} + +static void noinline_for_stack +cleanup_write_cache_enospc(struct inode *inode, + struct btrfs_io_ctl *io_ctl, + struct extent_state **cached_state, + struct list_head *bitmap_list) +{ io_ctl_drop_pages(io_ctl); unlock_extent_cached(&BTRFS_I(inode)->io_tree, 0, i_size_read(inode) - 1, cached_state, @@ -1266,11 +1271,8 @@ static int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode, ret = write_cache_extent_entries(io_ctl, ctl, block_group, &entries, &bitmaps, &bitmap_list); - spin_unlock(&ctl->tree_lock); - if (ret) { - mutex_unlock(&ctl->cache_writeout_mutex); - goto out_nospc; - } + if (ret) + goto out_nospc_locked; /* * Some spaces that are freed in the current transaction are pinned, @@ -1281,17 +1283,14 @@ static int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode, * the dirty list and redo it. No locking needed */ ret = write_pinned_extent_entries(root, block_group, io_ctl, &entries); - if (ret) { - mutex_unlock(&ctl->cache_writeout_mutex); - goto out_nospc; - } + if (ret) + goto out_nospc_locked; /* * At last, we write out all the bitmaps and keep cache_writeout_mutex * locked while doing it because a concurrent trim can be manipulating * or freeing the bitmap. */ - spin_lock(&ctl->tree_lock); ret = write_bitmap_entries(io_ctl, &bitmap_list); spin_unlock(&ctl->tree_lock); mutex_unlock(&ctl->cache_writeout_mutex); @@ -1344,6 +1343,11 @@ out: iput(inode); return ret; +out_nospc_locked: + cleanup_bitmap_list(&bitmap_list); + spin_unlock(&ctl->tree_lock); + mutex_unlock(&ctl->cache_writeout_mutex); + out_nospc: cleanup_write_cache_enospc(inode, io_ctl, &cached_state, &bitmap_list); -- 2.20.1