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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 22/32] cachefiles: Implement read and write parts of new I/O API From: David Howells To: Trond Myklebust , Anna Schumaker , Steve French , Alexander Viro , Matthew Wilcox Cc: Jeff Layton , Dave Wysochanski , dhowells@redhat.com, linux-cachefs@redhat.com, linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs-developer@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Mon, 13 Jul 2020 17:34:45 +0100 Message-ID: <159465808553.1376674.11788737980809596736.stgit@warthog.procyon.org.uk> In-Reply-To: <159465784033.1376674.18106463693989811037.stgit@warthog.procyon.org.uk> References: <159465784033.1376674.18106463693989811037.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.22 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Implement writing into the cache and reading back from the cache inside cachefiles using asynchronous direct I/O from the specified iterator. The size and position of the request should be aligned to the reported dio_block_size. Errors and completion are reported by callback. Signed-off-by: David Howells --- fs/cachefiles/io.c | 208 +++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 202 insertions(+), 6 deletions(-) diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c index ddb44ec5a199..42e0d620d778 100644 --- a/fs/cachefiles/io.c +++ b/fs/cachefiles/io.c @@ -12,30 +12,226 @@ #include #include "internal.h" +struct cachefiles_kiocb { + struct kiocb iocb; + struct fscache_io_request *req; + refcount_t ki_refcnt; +}; + +static inline void cachefiles_put_kiocb(struct cachefiles_kiocb *ki) +{ + if (refcount_dec_and_test(&ki->ki_refcnt)) { + fscache_put_io_request(ki->req); + fput(ki->iocb.ki_filp); + kfree(ki); + } +} + +/* + * Handle completion of a read from the cache. + */ +static void cachefiles_read_complete(struct kiocb *iocb, long ret, long ret2) +{ + struct cachefiles_kiocb *ki = container_of(iocb, struct cachefiles_kiocb, iocb); + struct fscache_io_request *req = ki->req; + + _enter("%llx,%ld,%ld", req->len, ret, ret2); + + fscache_end_io_operation(req->cookie); + + if (ret < 0) { + req->error = ret; + } else if (ret != req->len) { + req->error = -ENODATA; + } else { + req->transferred = ret; + set_bit(FSCACHE_IO_DATA_FROM_CACHE, &req->flags); + } + if (req->io_done) + req->io_done(req); + cachefiles_put_kiocb(ki); +} + /* * Initiate a read from the cache. */ -int cachefiles_read(struct fscache_object *object, +int cachefiles_read(struct fscache_object *obj, struct fscache_io_request *req, struct iov_iter *iter) { - req->error = -ENODATA; + struct cachefiles_object *object = + container_of(obj, struct cachefiles_object, fscache); + struct cachefiles_kiocb *ki; + struct file *file = object->backing_file; + ssize_t ret = -ENOBUFS; + + _enter("%pD,%li,%llx,%llx/%llx", + file, file_inode(file)->i_ino, req->pos, req->len, i_size_read(file->f_inode)); + + ki = kzalloc(sizeof(struct cachefiles_kiocb), GFP_KERNEL); + if (!ki) + goto presubmission_error; + + refcount_set(&ki->ki_refcnt, 2); + ki->iocb.ki_filp = get_file(file); + ki->iocb.ki_pos = req->pos; + ki->iocb.ki_flags = IOCB_DIRECT; + ki->iocb.ki_hint = ki_hint_validate(file_write_hint(file)); + ki->iocb.ki_ioprio = get_current_ioprio(); + ki->req = req; + + if (req->io_done) + ki->iocb.ki_complete = cachefiles_read_complete; + + ret = rw_verify_area(READ, file, &ki->iocb.ki_pos, iov_iter_count(iter)); + if (ret < 0) + goto presubmission_error_free; + + fscache_get_io_request(req); + ret = call_read_iter(file, &ki->iocb, iter); + switch (ret) { + case -EIOCBQUEUED: + goto in_progress; + + case -ERESTARTSYS: + case -ERESTARTNOINTR: + case -ERESTARTNOHAND: + case -ERESTART_RESTARTBLOCK: + /* There's no easy way to restart the syscall since other AIO's + * may be already running. Just fail this IO with EINTR. + */ + ret = -EINTR; + /* Fall through */ + default: + cachefiles_read_complete(&ki->iocb, ret, 0); + if (ret > 0) + ret = 0; + break; + } + +in_progress: + cachefiles_put_kiocb(ki); + _leave(" = %zd", ret); + return ret; + +presubmission_error_free: + fput(file); + kfree(ki); +presubmission_error: + req->error = -ENOMEM; + if (req->io_done) + req->io_done(req); + return -ENOMEM; +} + +/* + * Handle completion of a write to the cache. + */ +static void cachefiles_write_complete(struct kiocb *iocb, long ret, long ret2) +{ + struct cachefiles_kiocb *ki = container_of(iocb, struct cachefiles_kiocb, iocb); + struct fscache_io_request *req = ki->req; + struct inode *inode = file_inode(ki->iocb.ki_filp); + + _enter("%llx,%ld,%ld", req->len, ret, ret2); + + /* Tell lockdep we inherited freeze protection from submission thread */ + __sb_writers_acquired(inode->i_sb, SB_FREEZE_WRITE); + __sb_end_write(inode->i_sb, SB_FREEZE_WRITE); + + fscache_end_io_operation(req->cookie); + + if (ret < 0) + req->error = ret; + else if (ret != req->len) + req->error = -ENOBUFS; + else + cachefiles_mark_content_map(req); if (req->io_done) req->io_done(req); - return -ENODATA; + cachefiles_put_kiocb(ki); } /* * Initiate a write to the cache. */ -int cachefiles_write(struct fscache_object *object, +int cachefiles_write(struct fscache_object *obj, struct fscache_io_request *req, struct iov_iter *iter) { - req->error = -ENOBUFS; + struct cachefiles_object *object = + container_of(obj, struct cachefiles_object, fscache); + struct cachefiles_kiocb *ki; + struct inode *inode; + struct file *file = object->backing_file; + ssize_t ret = -ENOBUFS; + + _enter("%pD,%li,%llx,%llx/%llx", + file, file_inode(file)->i_ino, req->pos, req->len, i_size_read(file->f_inode)); + + ki = kzalloc(sizeof(struct cachefiles_kiocb), GFP_KERNEL); + if (!ki) + goto presubmission_error; + + refcount_set(&ki->ki_refcnt, 2); + ki->iocb.ki_filp = get_file(file); + ki->iocb.ki_pos = req->pos; + ki->iocb.ki_flags = IOCB_DIRECT | IOCB_WRITE; + ki->iocb.ki_hint = ki_hint_validate(file_write_hint(file)); + ki->iocb.ki_ioprio = get_current_ioprio(); + ki->req = req; + + if (req->io_done) + ki->iocb.ki_complete = cachefiles_write_complete; + + ret = rw_verify_area(WRITE, file, &ki->iocb.ki_pos, iov_iter_count(iter)); + if (ret < 0) + goto presubmission_error_free; + + /* Open-code file_start_write here to grab freeze protection, which + * will be released by another thread in aio_complete_rw(). Fool + * lockdep by telling it the lock got released so that it doesn't + * complain about the held lock when we return to userspace. + */ + inode = file_inode(file); + __sb_start_write(inode->i_sb, SB_FREEZE_WRITE, true); + __sb_writers_release(inode->i_sb, SB_FREEZE_WRITE); + + fscache_get_io_request(req); + ret = call_write_iter(file, &ki->iocb, iter); + switch (ret) { + case -EIOCBQUEUED: + goto in_progress; + + case -ERESTARTSYS: + case -ERESTARTNOINTR: + case -ERESTARTNOHAND: + case -ERESTART_RESTARTBLOCK: + /* There's no easy way to restart the syscall since other AIO's + * may be already running. Just fail this IO with EINTR. + */ + ret = -EINTR; + /* Fall through */ + default: + cachefiles_write_complete(&ki->iocb, ret, 0); + if (ret > 0) + ret = 0; + break; + } + +in_progress: + cachefiles_put_kiocb(ki); + _leave(" = %zd", ret); + return ret; + +presubmission_error_free: + fput(file); + kfree(ki); +presubmission_error: + req->error = -ENOMEM; if (req->io_done) req->io_done(req); - return -ENOBUFS; + return -ENOMEM; } /*