Messages in this thread Patch in this message | | | Subject | [PATCH 3/5] fuse: wait for end of IO on release | From | Maxim Patlasov <> | Date | Thu, 25 Sep 2014 16:06:34 +0400 |
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There are two types of I/O activity that can be "in progress" at the time of fuse_release() execution: asynchronous read-ahead and write-back. The patch ensures that they are completed before fuse_release_common sends FUSE_RELEASE to userspace.
So far as fuse_release() waits for end of async I/O, its callbacks (fuse_readpages_end and fuse_writepage_finish) calling fuse_file_put cannot be the last holders of fuse file anymore. To emphasize the fact, the patch replaces fuse_file_put with __fuse_file_put there.
Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com> --- fs/fuse/file.c | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 66 insertions(+), 5 deletions(-)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 7723b3f..8713e62 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -149,6 +149,17 @@ static void fuse_file_put(struct fuse_file *ff, bool sync) } } +/* + * Asynchronous callbacks may use it instead of fuse_file_put() because + * we guarantee that they are never last holders of ff. Hitting BUG() below + * will make clear any violation of the guarantee. + */ +static void __fuse_file_put(struct fuse_file *ff) +{ + if (atomic_dec_and_test(&ff->count)) + BUG(); +} + int fuse_do_open(struct fuse_conn *fc, u64 nodeid, struct file *file, bool isdir) { @@ -279,6 +290,11 @@ static void fuse_prepare_release(struct fuse_file *ff, int flags, int opcode) req->in.args[0].value = inarg; } +static bool must_release_synchronously(struct fuse_file *ff) +{ + return ff->open_flags & FOPEN_SYNC_RELEASE; +} + void fuse_release_common(struct file *file, int opcode) { struct fuse_file *ff; @@ -302,6 +318,13 @@ void fuse_release_common(struct file *file, int opcode) req->misc.release.path = file->f_path; /* + * No more in-flight asynchronous READ or WRITE requests if + * fuse file release is synchronous + */ + if (must_release_synchronously(ff)) + BUG_ON(atomic_read(&ff->count) != 1); + + /* * Normally this will send the RELEASE request, however if * some asynchronous READ or WRITE requests are outstanding, * the sending will be delayed. @@ -321,11 +344,34 @@ static int fuse_open(struct inode *inode, struct file *file) static int fuse_release(struct inode *inode, struct file *file) { struct fuse_conn *fc = get_fuse_conn(inode); + struct fuse_file *ff = file->private_data; /* see fuse_vma_close() for !writeback_cache case */ if (fc->writeback_cache) write_inode_now(inode, 1); + if (must_release_synchronously(ff)) { + struct fuse_inode *fi = get_fuse_inode(inode); + + /* + * Must remove file from write list. Otherwise it is possible + * this file will get more writeback from another files + * rerouted via write_files. + */ + spin_lock(&ff->fc->lock); + list_del_init(&ff->write_entry); + spin_unlock(&ff->fc->lock); + + wait_event(fi->page_waitq, atomic_read(&ff->count) == 1); + + /* + * spin_unlock_wait(&ff->fc->lock) would be natural here to + * wait for threads just released ff to leave their critical + * sections. But taking spinlock is the first thing + * fuse_release_common does, so that this is unnecessary. + */ + } + fuse_release_common(file, FUSE_RELEASE); /* return value is ignored by VFS */ @@ -823,8 +869,15 @@ static void fuse_readpages_end(struct fuse_conn *fc, struct fuse_req *req) unlock_page(page); page_cache_release(page); } - if (req->ff) - fuse_file_put(req->ff, false); + if (req->ff) { + if (must_release_synchronously(req->ff)) { + struct fuse_inode *fi = get_fuse_inode(req->inode); + + __fuse_file_put(req->ff); + wake_up(&fi->page_waitq); + } else + fuse_file_put(req->ff, false); + } } struct fuse_fill_data { @@ -851,6 +904,7 @@ static void fuse_send_readpages(struct fuse_fill_data *data) if (fc->async_read) { req->ff = fuse_file_get(ff); req->end = fuse_readpages_end; + req->inode = data->inode; fuse_request_send_background(fc, req); } else { fuse_request_send(fc, req); @@ -1502,7 +1556,7 @@ static void fuse_writepage_free(struct fuse_conn *fc, struct fuse_req *req) for (i = 0; i < req->num_pages; i++) __free_page(req->pages[i]); - if (req->ff) + if (req->ff && !must_release_synchronously(req->ff)) fuse_file_put(req->ff, false); } @@ -1519,6 +1573,8 @@ static void fuse_writepage_finish(struct fuse_conn *fc, struct fuse_req *req) dec_zone_page_state(req->pages[i], NR_WRITEBACK_TEMP); bdi_writeout_inc(bdi); } + if (must_release_synchronously(req->ff)) + __fuse_file_put(req->ff); wake_up(&fi->page_waitq); } @@ -1659,8 +1715,13 @@ int fuse_write_inode(struct inode *inode, struct writeback_control *wbc) ff = __fuse_write_file_get(fc, fi); err = fuse_flush_times(inode, ff); - if (ff) - fuse_file_put(ff, 0); + if (ff) { + if (must_release_synchronously(ff)) { + __fuse_file_put(ff); + wake_up(&fi->page_waitq); + } else + fuse_file_put(ff, false); + } return err; }
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