lkml.org 
[lkml]   [2018]   [Sep]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[Patch v3 14/16] CIFS: Add support for direct I/O read
Date
From: Long Li <longli@microsoft.com>

With direct I/O read, we transfer the data directly from transport layer to
the user data buffer.

Change in v3: added support for kernel AIO

Signed-off-by: Long Li <longli@microsoft.com>
---
fs/cifs/cifsfs.h | 1 +
fs/cifs/cifsglob.h | 5 ++
fs/cifs/file.c | 209 +++++++++++++++++++++++++++++++++++++++++++++--------
3 files changed, 186 insertions(+), 29 deletions(-)

diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
index 5f02318..7fba9aa 100644
--- a/fs/cifs/cifsfs.h
+++ b/fs/cifs/cifsfs.h
@@ -102,6 +102,7 @@ extern int cifs_open(struct inode *inode, struct file *file);
extern int cifs_close(struct inode *inode, struct file *file);
extern int cifs_closedir(struct inode *inode, struct file *file);
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_strict_writev(struct kiocb *iocb, struct iov_iter *from);
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 7f62c98..52248dd 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1146,6 +1146,11 @@ struct cifs_aio_ctx {
unsigned int len;
unsigned int total_len;
bool should_dirty;
+ /*
+ * Indicates if this aio_ctx is for direct_io,
+ * If yes, iter is a copy of the user passed iov_iter
+ */
+ bool direct_io;
};

struct cifs_readdata;
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 87eece6..476b2a1 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2965,7 +2965,6 @@ cifs_uncached_readdata_release(struct kref *refcount)
kref_put(&rdata->ctx->refcount, cifs_aio_ctx_release);
for (i = 0; i < rdata->nr_pages; i++) {
put_page(rdata->pages[i]);
- rdata->pages[i] = NULL;
}
cifs_readdata_release(refcount);
}
@@ -3004,7 +3003,7 @@ cifs_readdata_to_iov(struct cifs_readdata *rdata, struct iov_iter *iter)
return remaining ? -EFAULT : 0;
}

-static void collect_uncached_read_data(struct cifs_aio_ctx *ctx);
+static void collect_uncached_read_data(struct cifs_readdata *rdata, struct cifs_aio_ctx *ctx);

static void
cifs_uncached_readv_complete(struct work_struct *work)
@@ -3013,7 +3012,7 @@ cifs_uncached_readv_complete(struct work_struct *work)
struct cifs_readdata, work);

complete(&rdata->done);
- collect_uncached_read_data(rdata->ctx);
+ collect_uncached_read_data(rdata, rdata->ctx);
/* the below call can possibly free the last ref to aio ctx */
kref_put(&rdata->refcount, cifs_uncached_readdata_release);
}
@@ -3103,6 +3102,9 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,
int rc;
pid_t pid;
struct TCP_Server_Info *server;
+ struct page **pagevec;
+ size_t start;
+ struct iov_iter direct_iov = ctx->iter;

server = tlink_tcon(open_file->tlink)->ses->server;

@@ -3111,6 +3113,9 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,
else
pid = current->tgid;

+ if (ctx->direct_io)
+ iov_iter_advance(&direct_iov, offset - ctx->pos);
+
do {
rc = server->ops->wait_mtu_credits(server, cifs_sb->rsize,
&rsize, &credits);
@@ -3118,20 +3123,56 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,
break;

cur_len = min_t(const size_t, len, rsize);
- npages = DIV_ROUND_UP(cur_len, PAGE_SIZE);

- /* allocate a readdata struct */
- rdata = cifs_readdata_alloc(npages,
+ if (ctx->direct_io) {
+
+ cur_len = iov_iter_get_pages_alloc(
+ &direct_iov, &pagevec,
+ cur_len, &start);
+ if (cur_len < 0) {
+ cifs_dbg(VFS,
+ "couldn't get user pages (cur_len=%zd)"
+ " iter type %d"
+ " iov_offset %lu count %lu\n",
+ cur_len, direct_iov.type, direct_iov.iov_offset,
+ direct_iov.count);
+ dump_stack();
+ break;
+ }
+ iov_iter_advance(&direct_iov, cur_len);
+
+ rdata = cifs_readdata_direct_alloc(
+ pagevec, cifs_uncached_readv_complete);
+ if (!rdata) {
+ add_credits_and_wake_if(server, credits, 0);
+ rc = -ENOMEM;
+ break;
+ }
+
+ npages = (cur_len + start + PAGE_SIZE-1) / PAGE_SIZE;
+ rdata->page_offset = start;
+ rdata->tailsz = npages > 1 ?
+ cur_len-(PAGE_SIZE-start)-(npages-2)*PAGE_SIZE :
+ cur_len;
+
+ } else {
+
+ npages = DIV_ROUND_UP(cur_len, PAGE_SIZE);
+ /* allocate a readdata struct */
+ rdata = cifs_readdata_alloc(npages,
cifs_uncached_readv_complete);
- if (!rdata) {
- add_credits_and_wake_if(server, credits, 0);
- rc = -ENOMEM;
- break;
- }
+ if (!rdata) {
+ add_credits_and_wake_if(server, credits, 0);
+ rc = -ENOMEM;
+ break;
+ }

- rc = cifs_read_allocate_pages(rdata, npages);
- if (rc)
- goto error;
+ rc = cifs_read_allocate_pages(rdata, npages);
+ if (rc)
+ goto error;
+
+ rdata->tailsz = PAGE_SIZE;
+ }

rdata->cfile = cifsFileInfo_get(open_file);
rdata->nr_pages = npages;
@@ -3139,7 +3180,6 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,
rdata->bytes = cur_len;
rdata->pid = pid;
rdata->pagesz = PAGE_SIZE;
- rdata->tailsz = PAGE_SIZE;
rdata->read_into_pages = cifs_uncached_read_into_pages;
rdata->copy_into_pages = cifs_uncached_copy_into_pages;
rdata->credits = credits;
@@ -3153,13 +3193,17 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,
if (rc) {
add_credits_and_wake_if(server, rdata->credits, 0);
kref_put(&rdata->refcount,
- cifs_uncached_readdata_release);
- if (rc == -EAGAIN)
+ cifs_uncached_readdata_release);
+ if (rc == -EAGAIN) {
+ iov_iter_revert(&direct_iov, cur_len);
continue;
+ }
break;
}

- list_add_tail(&rdata->list, rdata_list);
+ /* Add to aio pending list if it's not there */
+ if (rdata_list)
+ list_add_tail(&rdata->list, rdata_list);
offset += cur_len;
len -= cur_len;
} while (len > 0);
@@ -3168,7 +3212,7 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,
}

static void
-collect_uncached_read_data(struct cifs_aio_ctx *ctx)
+collect_uncached_read_data(struct cifs_readdata *uncached_rdata, struct cifs_aio_ctx *ctx)
{
struct cifs_readdata *rdata, *tmp;
struct iov_iter *to = &ctx->iter;
@@ -3211,10 +3255,12 @@ collect_uncached_read_data(struct cifs_aio_ctx *ctx)
* reading.
*/
if (got_bytes && got_bytes < rdata->bytes) {
- rc = cifs_readdata_to_iov(rdata, to);
+ rc = 0;
+ if (!ctx->direct_io)
+ rc = cifs_readdata_to_iov(rdata, to);
if (rc) {
kref_put(&rdata->refcount,
- cifs_uncached_readdata_release);
+ cifs_uncached_readdata_release);
continue;
}
}
@@ -3228,28 +3274,32 @@ collect_uncached_read_data(struct cifs_aio_ctx *ctx)
list_splice(&tmp_list, &ctx->list);

kref_put(&rdata->refcount,
- cifs_uncached_readdata_release);
+ cifs_uncached_readdata_release);
goto again;
} else if (rdata->result)
rc = rdata->result;
- else
+ else if (!ctx->direct_io)
rc = cifs_readdata_to_iov(rdata, to);

/* if there was a short read -- discard anything left */
if (rdata->got_bytes && rdata->got_bytes < rdata->bytes)
rc = -ENODATA;
+
+ ctx->total_len += rdata->got_bytes;
}
list_del_init(&rdata->list);
kref_put(&rdata->refcount, cifs_uncached_readdata_release);
}

- for (i = 0; i < ctx->npages; i++) {
- if (ctx->should_dirty)
- set_page_dirty(ctx->bv[i].bv_page);
- put_page(ctx->bv[i].bv_page);
- }
+ if (!ctx->direct_io) {
+ for (i = 0; i < ctx->npages; i++) {
+ if (ctx->should_dirty)
+ set_page_dirty(ctx->bv[i].bv_page);
+ put_page(ctx->bv[i].bv_page);
+ }

- ctx->total_len = ctx->len - iov_iter_count(to);
+ ctx->total_len = ctx->len - iov_iter_count(to);
+ }

cifs_stats_bytes_read(tcon, ctx->total_len);

@@ -3267,6 +3317,107 @@ collect_uncached_read_data(struct cifs_aio_ctx *ctx)
complete(&ctx->done);
}

+ssize_t cifs_direct_readv(struct kiocb *iocb, struct iov_iter *to)
+{
+ size_t len;
+ struct file *file;
+ struct cifs_sb_info *cifs_sb;
+ struct cifsFileInfo *cfile;
+ struct cifs_tcon *tcon;
+ ssize_t rc, total_read = 0;
+ struct TCP_Server_Info *server;
+ loff_t offset = iocb->ki_pos;
+ pid_t pid;
+ struct cifs_aio_ctx *ctx;
+
+ /*
+ * iov_iter_get_pages_alloc() doesn't work with ITER_KVEC,
+ * fall back to data copy read path
+ */
+ if (to->type & ITER_KVEC) {
+ cifs_dbg(FYI, "use non-direct cifs_user_readv for kvec I/O\n");
+ return cifs_user_readv(iocb, to);
+ }
+
+ len = iov_iter_count(to);
+ if (!len)
+ return 0;
+
+ file = iocb->ki_filp;
+ cifs_sb = CIFS_FILE_SB(file);
+ cfile = file->private_data;
+ tcon = tlink_tcon(cfile->tlink);
+ server = tcon->ses->server;
+
+ if (!server->ops->async_readv)
+ return -ENOSYS;
+
+ if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_RWPIDFORWARD)
+ pid = cfile->pid;
+ else
+ pid = current->tgid;
+
+ if ((file->f_flags & O_ACCMODE) == O_WRONLY)
+ cifs_dbg(FYI, "attempting read on write only file instance\n");
+
+ ctx = cifs_aio_ctx_alloc();
+ if (!ctx)
+ return -ENOMEM;
+
+ ctx->cfile = cifsFileInfo_get(cfile);
+
+ if (!is_sync_kiocb(iocb))
+ ctx->iocb = iocb;
+
+ if (to->type == ITER_IOVEC)
+ ctx->should_dirty = true;
+
+ ctx->pos = offset;
+ ctx->direct_io = true;
+ ctx->iter = *to;
+ ctx->len = len;
+
+ /* grab a lock here due to read response handlers can access ctx */
+ mutex_lock(&ctx->aio_mutex);
+
+ rc = cifs_send_async_read(offset, len, cfile, cifs_sb, &ctx->list, ctx);
+
+ /* if at least one read request send succeeded, then reset rc */
+ if (!list_empty(&ctx->list))
+ rc = 0;
+
+ mutex_unlock(&ctx->aio_mutex);
+
+ if (rc) {
+ kref_put(&ctx->refcount, cifs_aio_ctx_release);
+ return rc;
+ }
+
+ if (!is_sync_kiocb(iocb)) {
+ kref_put(&ctx->refcount, cifs_aio_ctx_release);
+ return -EIOCBQUEUED;
+ }
+
+ rc = wait_for_completion_killable(&ctx->done);
+ if (rc) {
+ mutex_lock(&ctx->aio_mutex);
+ ctx->rc = rc = -EINTR;
+ total_read = ctx->total_len;
+ mutex_unlock(&ctx->aio_mutex);
+ } else {
+ rc = ctx->rc;
+ total_read = ctx->total_len;
+ }
+
+ kref_put(&ctx->refcount, cifs_aio_ctx_release);
+
+ if (total_read) {
+ iocb->ki_pos += total_read;
+ return total_read;
+ }
+ return rc;
+}
+
ssize_t cifs_user_readv(struct kiocb *iocb, struct iov_iter *to)
{
struct file *file = iocb->ki_filp;
--
2.7.4
\
 
 \ /
  Last update: 2018-09-08 04:17    [W:0.093 / U:0.460 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site