Btrfs: fix -ENOSPC on block group removal
Unlike when attempting to allocate a new block group, where we check that we have enough space in the system space_info to update the device items and insert a new chunk item in the chunk tree, we were not checking if the system space_info had enough space for updating the device items and deleting the chunk item in the chunk tree. This often lead to -ENOSPC error when attempting to allocate blocks for the chunk tree (during btree node/leaf COW operations) while updating the device items or deleting the chunk item, which resulted in the current transaction being aborted and turning the filesystem into read-only mode. While running fstests generic/038, which stresses allocation of block groups and removal of unused block groups, with a large scratch device (750Gb) this happened often, despite more than enough unallocated space, and resulted in the following trace: [68663.586604] WARNING: CPU: 3 PID: 1521 at fs/btrfs/super.c:260 __btrfs_abort_transaction+0x52/0x114 [btrfs]() [68663.600407] BTRFS: Transaction aborted (error -28) (...) [68663.730829] Call Trace: [68663.732585] [<ffffffff8142fa46>] dump_stack+0x4f/0x7b [68663.734334] [<ffffffff8108b6a2>] ? console_unlock+0x361/0x3ad [68663.739980] [<ffffffff81045ea5>] warn_slowpath_common+0xa1/0xbb [68663.757153] [<ffffffffa036ca6d>] ? __btrfs_abort_transaction+0x52/0x114 [btrfs] [68663.760925] [<ffffffff81045f05>] warn_slowpath_fmt+0x46/0x48 [68663.762854] [<ffffffffa03b159d>] ? btrfs_update_device+0x15a/0x16c [btrfs] [68663.764073] [<ffffffffa036ca6d>] __btrfs_abort_transaction+0x52/0x114 [btrfs] [68663.765130] [<ffffffffa03b3638>] btrfs_remove_chunk+0x597/0x5ee [btrfs] [68663.765998] [<ffffffffa0384663>] ? btrfs_delete_unused_bgs+0x245/0x296 [btrfs] [68663.767068] [<ffffffffa0384676>] btrfs_delete_unused_bgs+0x258/0x296 [btrfs] [68663.768227] [<ffffffff8143527f>] ? _raw_spin_unlock_irq+0x2d/0x4c [68663.769081] [<ffffffffa038b109>] cleaner_kthread+0x13d/0x16c [btrfs] [68663.799485] [<ffffffffa038afcc>] ? btrfs_alloc_root+0x28/0x28 [btrfs] [68663.809208] [<ffffffff8105f367>] kthread+0xef/0xf7 [68663.828795] [<ffffffff810e603f>] ? time_hardirqs_on+0x15/0x28 [68663.844942] [<ffffffff8105f278>] ? __kthread_parkme+0xad/0xad [68663.846486] [<ffffffff81435a88>] ret_from_fork+0x58/0x90 [68663.847760] [<ffffffff8105f278>] ? __kthread_parkme+0xad/0xad [68663.849503] ---[ end trace 798477c6d6dbaad6 ]--- [68663.850525] BTRFS: error (device sdc) in btrfs_remove_chunk:2652: errno=-28 No space left So fix this by verifying that enough space exists in system space_info, and reserving the space in the chunk block reserve, before attempting to delete the block group and allocate a new system chunk if we don't have enough space to perform the necessary updates and delete in the chunk tree. Like for the block group creation case, we don't error our if we fail to allocate a new system chunk, since we might end up not needing it (no node/leaf splits happen during the COW operations and/or we end up not needing to COW any btree nodes or leafs because they were already COWed in the current transaction and their writeback didn't start yet). Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Chris Mason <clm@fb.com>
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