From ea8cd33390fafc1eca06a26e6a9c7bf1d386526f Mon Sep 17 00:00:00 2001 From: Pavel Emelyanov Date: Thu, 10 Oct 2013 17:12:05 +0400 Subject: [PATCH] fuse: Fix O_DIRECT operations vs cached writeback misorder The problem is: 1. write cached data to a file 2. read directly from the same file (via another fd) The 2nd operation may read stale data, i.e. the one that was in a file before the 1st op. Problem is in how fuse manages writeback. When direct op occurs the core kernel code calls filemap_write_and_wait to flush all the cached ops in flight. But fuse acks the writeback right after the ->writepages callback exits w/o waiting for the real write to happen. Thus the subsequent direct op proceeds while the real writeback is still in flight. This is a problem for backends that reorder operation. Fix this by making the fuse direct IO callback explicitly wait on the in-flight writeback to finish. Signed-off-by: Maxim Patlasov Signed-off-by: Miklos Szeredi --- fs/fuse/cuse.c | 5 +++-- fs/fuse/file.c | 32 ++++++++++++++++++++++++++------ fs/fuse/fuse_i.h | 13 ++++++++++++- 3 files changed, 41 insertions(+), 9 deletions(-) diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c index b96a49b37d66..23e363f38302 100644 --- a/fs/fuse/cuse.c +++ b/fs/fuse/cuse.c @@ -95,7 +95,7 @@ static ssize_t cuse_read(struct file *file, char __user *buf, size_t count, struct iovec iov = { .iov_base = buf, .iov_len = count }; struct fuse_io_priv io = { .async = 0, .file = file }; - return fuse_direct_io(&io, &iov, 1, count, &pos, 0); + return fuse_direct_io(&io, &iov, 1, count, &pos, FUSE_DIO_CUSE); } static ssize_t cuse_write(struct file *file, const char __user *buf, @@ -109,7 +109,8 @@ static ssize_t cuse_write(struct file *file, const char __user *buf, * No locking or generic_write_checks(), the server is * responsible for locking and sanity checks. */ - return fuse_direct_io(&io, &iov, 1, count, &pos, 1); + return fuse_direct_io(&io, &iov, 1, count, &pos, + FUSE_DIO_WRITE | FUSE_DIO_CUSE); } static int cuse_open(struct inode *inode, struct file *file) diff --git a/fs/fuse/file.c b/fs/fuse/file.c index d93f2a1aa7de..276433021561 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -358,12 +358,13 @@ u64 fuse_lock_owner_id(struct fuse_conn *fc, fl_owner_t id) } /* - * Check if page is under writeback + * Check if any page in a range is under writeback * * This is currently done by walking the list of writepage requests * for the inode, which can be pretty inefficient. */ -static bool fuse_page_is_writeback(struct inode *inode, pgoff_t index) +static bool fuse_range_is_writeback(struct inode *inode, pgoff_t idx_from, + pgoff_t idx_to) { struct fuse_conn *fc = get_fuse_conn(inode); struct fuse_inode *fi = get_fuse_inode(inode); @@ -376,8 +377,8 @@ static bool fuse_page_is_writeback(struct inode *inode, pgoff_t index) BUG_ON(req->inode != inode); curr_index = req->misc.write.in.offset >> PAGE_CACHE_SHIFT; - if (curr_index <= index && - index < curr_index + req->num_pages) { + if (idx_from < curr_index + req->num_pages && + curr_index <= idx_to) { found = true; break; } @@ -387,6 +388,11 @@ static bool fuse_page_is_writeback(struct inode *inode, pgoff_t index) return found; } +static inline bool fuse_page_is_writeback(struct inode *inode, pgoff_t index) +{ + return fuse_range_is_writeback(inode, index, index); +} + /* * Wait for page writeback to be completed. * @@ -1364,13 +1370,18 @@ static inline int fuse_iter_npages(const struct iov_iter *ii_p) ssize_t fuse_direct_io(struct fuse_io_priv *io, const struct iovec *iov, unsigned long nr_segs, size_t count, loff_t *ppos, - int write) + int flags) { + int write = flags & FUSE_DIO_WRITE; + int cuse = flags & FUSE_DIO_CUSE; struct file *file = io->file; + struct inode *inode = file->f_mapping->host; struct fuse_file *ff = file->private_data; struct fuse_conn *fc = ff->fc; size_t nmax = write ? fc->max_write : fc->max_read; loff_t pos = *ppos; + pgoff_t idx_from = pos >> PAGE_CACHE_SHIFT; + pgoff_t idx_to = (pos + count - 1) >> PAGE_CACHE_SHIFT; ssize_t res = 0; struct fuse_req *req; struct iov_iter ii; @@ -1384,6 +1395,14 @@ ssize_t fuse_direct_io(struct fuse_io_priv *io, const struct iovec *iov, if (IS_ERR(req)) return PTR_ERR(req); + if (!cuse && fuse_range_is_writeback(inode, idx_from, idx_to)) { + if (!write) + mutex_lock(&inode->i_mutex); + fuse_sync_writes(inode); + if (!write) + mutex_unlock(&inode->i_mutex); + } + while (count) { size_t nres; fl_owner_t owner = current->files; @@ -1472,7 +1491,8 @@ static ssize_t __fuse_direct_write(struct fuse_io_priv *io, res = generic_write_checks(file, ppos, &count, 0); if (!res) - res = fuse_direct_io(io, iov, nr_segs, count, ppos, 1); + res = fuse_direct_io(io, iov, nr_segs, count, ppos, + FUSE_DIO_WRITE); fuse_invalidate_attr(inode); diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index 1e6ad6d43051..a257ed8ebee6 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -868,9 +868,20 @@ int fuse_reverse_inval_entry(struct super_block *sb, u64 parent_nodeid, int fuse_do_open(struct fuse_conn *fc, u64 nodeid, struct file *file, bool isdir); + +/** + * fuse_direct_io() flags + */ + +/** If set, it is WRITE; otherwise - READ */ +#define FUSE_DIO_WRITE (1 << 0) + +/** CUSE pass fuse_direct_io() a file which f_mapping->host is not from FUSE */ +#define FUSE_DIO_CUSE (1 << 1) + ssize_t fuse_direct_io(struct fuse_io_priv *io, const struct iovec *iov, unsigned long nr_segs, size_t count, loff_t *ppos, - int write); + int flags); long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg, unsigned int flags); long fuse_ioctl_common(struct file *file, unsigned int cmd, -- 2.34.1