From 5b4a8fbe4b0bc1b0d88aaaefab27c7d031905cc1 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Fri, 22 Oct 2021 17:03:01 +0200 Subject: [PATCH] fuse: make sure reclaim doesn't write the inode commit 5c791fe1e2a4f401f819065ea4fc0450849f1818 upstream. In writeback cache mode mtime/ctime updates are cached, and flushed to the server using the ->write_inode() callback. Closing the file will result in a dirty inode being immediately written, but in other cases the inode can remain dirty after all references are dropped. This result in the inode being written back from reclaim, which can deadlock on a regular allocation while the request is being served. The usual mechanisms (GFP_NOFS/PF_MEMALLOC*) don't work for FUSE, because serving a request involves unrelated userspace process(es). Instead do the same as for dirty pages: make sure the inode is written before the last reference is gone. - fallocate(2)/copy_file_range(2): these call file_update_time() or file_modified(), so flush the inode before returning from the call - unlink(2), link(2) and rename(2): these call fuse_update_ctime(), so flush the ctime directly from this helper Reported-by: chenguanyou Signed-off-by: Miklos Szeredi Cc: Ed Tsai Signed-off-by: Greg Kroah-Hartman --- fs/fuse/dir.c | 8 ++++++++ fs/fuse/file.c | 15 +++++++++++++++ fs/fuse/fuse_i.h | 1 + fs/fuse/inode.c | 3 +++ 4 files changed, 27 insertions(+) diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index d9b977c0f38dc..2798fbe8d0018 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -738,11 +738,19 @@ static int fuse_symlink(struct user_namespace *mnt_userns, struct inode *dir, return create_new_entry(fm, &args, dir, entry, S_IFLNK); } +void fuse_flush_time_update(struct inode *inode) +{ + int err = sync_inode_metadata(inode, 1); + + mapping_set_error(inode->i_mapping, err); +} + void fuse_update_ctime(struct inode *inode) { if (!IS_NOCMTIME(inode)) { inode->i_ctime = current_time(inode); mark_inode_dirty_sync(inode); + fuse_flush_time_update(inode); } } diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 11404f8c21c75..5c5ed58d91a73 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -1848,6 +1848,17 @@ int fuse_write_inode(struct inode *inode, struct writeback_control *wbc) struct fuse_file *ff; int err; + /* + * Inode is always written before the last reference is dropped and + * hence this should not be reached from reclaim. + * + * Writing back the inode from reclaim can deadlock if the request + * processing itself needs an allocation. Allocations triggering + * reclaim while serving a request can't be prevented, because it can + * involve any number of unrelated userspace processes. + */ + WARN_ON(wbc->for_reclaim); + ff = __fuse_write_file_get(fi); err = fuse_flush_times(inode, ff); if (ff) @@ -3002,6 +3013,8 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset, if (lock_inode) inode_unlock(inode); + fuse_flush_time_update(inode); + return err; } @@ -3111,6 +3124,8 @@ static ssize_t __fuse_copy_file_range(struct file *file_in, loff_t pos_in, inode_unlock(inode_out); file_accessed(file_in); + fuse_flush_time_update(inode_out); + return err; } diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index f55f9f94b1a4f..a59e36c7deaea 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -1148,6 +1148,7 @@ int fuse_allow_current_process(struct fuse_conn *fc); u64 fuse_lock_owner_id(struct fuse_conn *fc, fl_owner_t id); +void fuse_flush_time_update(struct inode *inode); void fuse_update_ctime(struct inode *inode); int fuse_update_attributes(struct inode *inode, struct file *file); diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 12d49a1914e84..2f999d38c9b4a 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -118,6 +118,9 @@ static void fuse_evict_inode(struct inode *inode) { struct fuse_inode *fi = get_fuse_inode(inode); + /* Will write inode on close/munmap and in all other dirtiers */ + WARN_ON(inode->i_state & I_DIRTY_INODE); + truncate_inode_pages_final(&inode->i_data); clear_inode(inode); if (inode->i_sb->s_flags & SB_ACTIVE) {