This is a note to let you know that I've just added the patch titled

Btrfs: fix list_add corruption and soft lockups in fsync

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: btrfs-fix-list_add-corruption-and-soft-lockups-in-fsync.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Thu Feb 1 13:45:42 CET 2018

From: Liu Bo bo.li.liu@oracle.com Date: Tue, 21 Nov 2017 14:35:40 -0700 Subject: Btrfs: fix list_add corruption and soft lockups in fsync

From: Liu Bo bo.li.liu@oracle.com

[ Upstream commit ebb70442cdd4872260c2415929c456be3562da82 ]

Xfstests btrfs/146 revealed this corruption,

[ 58.138831] Buffer I/O error on dev dm-0, logical block 2621424, async page read [ 58.151233] BTRFS error (device sdf): bdev /dev/mapper/error-test errs: wr 1, rd 0, flush 0, corrupt 0, gen 0 [ 58.152403] list_add corruption. prev->next should be next (ffff88005e6775d8), but was ffffc9000189be88. (prev=ffffc9000189be88). [ 58.153518] ------------[ cut here ]------------ [ 58.153892] WARNING: CPU: 1 PID: 1287 at lib/list_debug.c:31 __list_add_valid+0x169/0x1f0 ... [ 58.157379] RIP: 0010:__list_add_valid+0x169/0x1f0 ... [ 58.161956] Call Trace: [ 58.162264] btrfs_log_inode_parent+0x5bd/0xfb0 [btrfs] [ 58.163583] btrfs_log_dentry_safe+0x60/0x80 [btrfs] [ 58.164003] btrfs_sync_file+0x4c2/0x6f0 [btrfs] [ 58.164393] vfs_fsync_range+0x5f/0xd0 [ 58.164898] do_fsync+0x5a/0x90 [ 58.165170] SyS_fsync+0x10/0x20 [ 58.165395] entry_SYSCALL_64_fastpath+0x1f/0xbe ...

It turns out that we could record btrfs_log_ctx:io_err in log_one_extents when IO fails, but make log_one_extents() return '0' instead of -EIO, so the IO error is not acknowledged by the callers, i.e. btrfs_log_inode_parent(), which would remove btrfs_log_ctx:list from list head 'root->log_ctxs'. Since btrfs_log_ctx is allocated from stack memory, it'd get freed with a object alive on the list. then a future list_add will throw the above warning.

This returns the correct error in the above case.

Jeff also reported this while testing against his fsync error patch set[1].

[1]: https://www.spinics.net/lists/linux-btrfs/msg65308.html "btrfs list corruption and soft lockups while testing writeback error handling"

Fixes: 8407f553268a4611f254 ("Btrfs: fix data corruption after fast fsync and writeback error") Signed-off-by: Liu Bo bo.li.liu@oracle.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/file.c | 5 +++-- fs/btrfs/tree-log.c | 2 +- 2 files changed, 4 insertions(+), 3 deletions(-)

--- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -2056,6 +2056,8 @@ int btrfs_sync_file(struct file *file, l len = (u64)end - (u64)start + 1; trace_btrfs_sync_file(file, datasync);

+ btrfs_init_log_ctx(&ctx, inode); + /* * We write the dirty pages in the range and wait until they complete * out of the ->i_mutex. If so, we can flush the dirty pages by @@ -2202,8 +2204,6 @@ int btrfs_sync_file(struct file *file, l } trans->sync = true;

- btrfs_init_log_ctx(&ctx, inode); - ret = btrfs_log_dentry_safe(trans, root, dentry, start, end, &ctx); if (ret < 0) { /* Fallthrough and commit/free transaction. */ @@ -2261,6 +2261,7 @@ int btrfs_sync_file(struct file *file, l ret = btrfs_end_transaction(trans); } out: + ASSERT(list_empty(&ctx.list)); err = file_check_and_advance_wb_err(file); if (!ret) ret = err; --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -4100,7 +4100,7 @@ static int log_one_extent(struct btrfs_t

if (ordered_io_err) { ctx->io_err = -EIO; - return 0; + return ctx->io_err; }

btrfs_init_map_token(&token);

Patches currently in stable-queue which might be from bo.li.liu@oracle.com are

queue-4.14/btrfs-bail-out-gracefully-rather-than-bug_on.patch queue-4.14/btrfs-fix-deadlock-when-writing-out-space-cache.patch queue-4.14/btrfs-fix-list_add-corruption-and-soft-lockups-in-fsync.patch