Re: [Patch v2 14/15] CIFS: Add support for direct I/O write
From: Tom Talpey
Date: Sat Jun 23 2018 - 22:48:28 EST
On 5/30/2018 3:48 PM, Long Li wrote:
From: Long Li <longli@xxxxxxxxxxxxx>
Implement the function for direct I/O write. It doesn't support AIO, which
will be implemented in a follow up patch.
Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
---
fs/cifs/cifsfs.h | 1 +
fs/cifs/file.c | 165 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 166 insertions(+)
diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
index 7fba9aa..e9c5103 100644
--- a/fs/cifs/cifsfs.h
+++ b/fs/cifs/cifsfs.h
@@ -105,6 +105,7 @@ extern ssize_t cifs_user_readv(struct kiocb *iocb, struct iov_iter *to);
extern ssize_t cifs_direct_readv(struct kiocb *iocb, struct iov_iter *to);
extern ssize_t cifs_strict_readv(struct kiocb *iocb, struct iov_iter *to);
extern ssize_t cifs_user_writev(struct kiocb *iocb, struct iov_iter *from);
+extern ssize_t cifs_direct_writev(struct kiocb *iocb, struct iov_iter *from);
extern ssize_t cifs_strict_writev(struct kiocb *iocb, struct iov_iter *from);
extern int cifs_lock(struct file *, int, struct file_lock *);
extern int cifs_fsync(struct file *, loff_t, loff_t, int);
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index e6e6f24..8c385b1 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2461,6 +2461,35 @@ cifs_uncached_writedata_release(struct kref *refcount)
static void collect_uncached_write_data(struct cifs_aio_ctx *ctx);
+static void cifs_direct_writedata_release(struct kref *refcount)
+{
+ int i;
+ struct cifs_writedata *wdata = container_of(refcount,
+ struct cifs_writedata, refcount);
+
+ for (i = 0; i < wdata->nr_pages; i++)
+ put_page(wdata->pages[i]);
+
+ cifs_writedata_release(refcount);
+}
+
+static void cifs_direct_writev_complete(struct work_struct *work)
+{
+ struct cifs_writedata *wdata = container_of(work,
+ struct cifs_writedata, work);
+ struct inode *inode = d_inode(wdata->cfile->dentry);
+ struct cifsInodeInfo *cifsi = CIFS_I(inode);
+
+ spin_lock(&inode->i_lock);
+ cifs_update_eof(cifsi, wdata->offset, wdata->bytes);
+ if (cifsi->server_eof > inode->i_size)
+ i_size_write(inode, cifsi->server_eof);
+ spin_unlock(&inode->i_lock);
+
+ complete(&wdata->done);
+ kref_put(&wdata->refcount, cifs_direct_writedata_release);
+}
+
static void
cifs_uncached_writev_complete(struct work_struct *work)
{
@@ -2703,6 +2732,142 @@ static void collect_uncached_write_data(struct cifs_aio_ctx *ctx)
complete(&ctx->done);
}
+ssize_t cifs_direct_writev(struct kiocb *iocb, struct iov_iter *from)
+{
+ struct file *file = iocb->ki_filp;
+ ssize_t total_written = 0;
+ struct cifsFileInfo *cfile;
+ struct cifs_tcon *tcon;
+ struct cifs_sb_info *cifs_sb;
+ struct TCP_Server_Info *server;
+ pid_t pid;
+ unsigned long nr_pages;
+ loff_t offset = iocb->ki_pos;
+ size_t len = iov_iter_count(from);
+ int rc;
+ struct cifs_writedata *wdata;
+
+ /*
+ * iov_iter_get_pages_alloc doesn't work with ITER_KVEC.
+ * In this case, fall back to non-direct write function.
+ */
+ if (from->type & ITER_KVEC) {
+ cifs_dbg(FYI, "use non-direct cifs_user_writev for kvec I/O\n");
+ return cifs_user_writev(iocb, from);
+ }
+
+ rc = generic_write_checks(iocb, from);
+ if (rc <= 0)
+ return rc;
+
+ cifs_sb = CIFS_FILE_SB(file);
+ cfile = file->private_data;
+ tcon = tlink_tcon(cfile->tlink);
+ server = tcon->ses->server;
+
+ if (!server->ops->async_writev)
+ return -ENOSYS;
+
+ if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_RWPIDFORWARD)
+ pid = cfile->pid;
+ else
+ pid = current->tgid;
+
+ do {
+ unsigned int wsize, credits;
+ struct page **pagevec;
+ size_t start;
+ ssize_t cur_len;
+
+ rc = server->ops->wait_mtu_credits(server, cifs_sb->wsize,
+ &wsize, &credits);
+ if (rc)
+ break;
+
+ cur_len = iov_iter_get_pages_alloc(
+ from, &pagevec, wsize, &start);
+ if (cur_len < 0) {
+ cifs_dbg(VFS,
+ "direct_writev couldn't get user pages "
+ "(rc=%zd) iter type %d iov_offset %lu count"
+ " %lu\n",
+ cur_len, from->type,
+ from->iov_offset, from->count);
+ dump_stack();
+ break;
+ }
+ if (cur_len < 0)
+ break;
This cur_len < 0 test is redundant with the prior if(), delete.
+
+ nr_pages = (cur_len + start + PAGE_SIZE - 1) / PAGE_SIZE;
Am I misreading, or will this return be one more page than needed? If
start (the first byte offset) is > 0, nr_pages will already be one.
And if cur_len is 4KB, even if start is 0, nr_pages will be two.
+
+ wdata = cifs_writedata_direct_alloc(pagevec,
+ cifs_direct_writev_complete);
+ if (!wdata) {
+ rc = -ENOMEM;
+ add_credits_and_wake_if(server, credits, 0);
+ break;
+ }
+
+ wdata->nr_pages = nr_pages;
+ wdata->page_offset = start;
+ wdata->pagesz = PAGE_SIZE;
+ wdata->tailsz =
+ nr_pages > 1 ?
+ cur_len - (PAGE_SIZE - start) -
+ (nr_pages - 2) * PAGE_SIZE :
+ cur_len;
+
+ wdata->sync_mode = WB_SYNC_ALL;
+ wdata->offset = (__u64)offset;
+ wdata->cfile = cifsFileInfo_get(cfile);
+ wdata->pid = pid;
+ wdata->bytes = cur_len;
+ wdata->credits = credits;
+
+ rc = 0;
+ if (wdata->cfile->invalidHandle)
+ rc = cifs_reopen_file(wdata->cfile, false);
+
+ if (!rc)
+ rc = server->ops->async_writev(wdata,
+ cifs_direct_writedata_release);
+
+ if (rc) {
+ add_credits_and_wake_if(server, wdata->credits, 0);
+ kref_put(&wdata->refcount,
+ cifs_direct_writedata_release);
+ if (rc == -EAGAIN)
+ continue;
+ break;
+ }
Same comments as for previous patch re the if (rc) ladder, and
the break/continues both being better expressed as careful goto's.
+
+ wait_for_completion(&wdata->done);
+ if (wdata->result) {
+ rc = wdata->result;
+ kref_put(&wdata->refcount,
+ cifs_direct_writedata_release);
+ if (rc == -EAGAIN)
+ continue;
+ break;
+ }
+
+ kref_put(&wdata->refcount, cifs_direct_writedata_release);
+
+ iov_iter_advance(from, cur_len);
+ total_written += cur_len;
+ offset += cur_len;
+ len -= cur_len;
+ } while (len);
+
+ if (unlikely(!total_written))
+ return rc;
+
+ iocb->ki_pos += total_written;
+ return total_written;
+
+}
+
ssize_t cifs_user_writev(struct kiocb *iocb, struct iov_iter *from)
{
struct file *file = iocb->ki_filp;