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CIFS: Add support for direct I/O read
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With direct I/O read, we transfer the data directly from transport layer to
the user data buffer.

Change in v3: add support for kernel AIO

Change in v4:
Refactor common read code to __cifs_readv for direct and non-direct I/O.
Retry on direct I/O failure.

Signed-off-by: Long Li <longli@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
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@longlimsft
longlimsft authored and Steve French committed Nov 2, 2018
1 parent 0df444a commit 6e6e2b8
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Showing 3 changed files with 192 additions and 39 deletions.
1 change: 1 addition & 0 deletions fs/cifs/cifsfs.h
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Original file line number Diff line number Diff line change
Expand Up @@ -101,6 +101,7 @@ 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);
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5 changes: 5 additions & 0 deletions fs/cifs/cifsglob.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1186,6 +1186,11 @@ 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;
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225 changes: 186 additions & 39 deletions fs/cifs/file.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2979,7 +2979,6 @@ 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);
}
Expand Down Expand Up @@ -3106,6 +3105,67 @@ cifs_uncached_copy_into_pages(struct TCP_Server_Info *server,
return uncached_fill_pages(server, rdata, iter, iter->count);
}

static int cifs_resend_rdata(struct cifs_readdata *rdata,
struct list_head *rdata_list,
struct cifs_aio_ctx *ctx)
{
int wait_retry = 0;
unsigned int rsize, credits;
int rc;
struct TCP_Server_Info *server =
tlink_tcon(rdata->cfile->tlink)->ses->server;

/*
* Try to resend this rdata, waiting for credits up to 3 seconds.
* Note: we are attempting to resend the whole rdata not in segments
*/
do {
rc = server->ops->wait_mtu_credits(server, rdata->bytes,
&rsize, &credits);

if (rc)
break;

if (rsize < rdata->bytes) {
add_credits_and_wake_if(server, credits, 0);
msleep(1000);
wait_retry++;
}
} while (rsize < rdata->bytes && wait_retry < 3);

/*
* If we can't find enough credits to send this rdata
* release the rdata and return failure, this will pass
* whatever I/O amount we have finished to VFS.
*/
if (rsize < rdata->bytes) {
rc = -EBUSY;
goto out;
}

rc = -EAGAIN;
while (rc == -EAGAIN) {
rc = 0;
if (rdata->cfile->invalidHandle)
rc = cifs_reopen_file(rdata->cfile, true);
if (!rc)
rc = server->ops->async_readv(rdata);
}

if (!rc) {
/* Add to aio pending list */
list_add_tail(&rdata->list, rdata_list);
return 0;
}

add_credits_and_wake_if(server, rdata->credits, 0);
out:
kref_put(&rdata->refcount,
cifs_uncached_readdata_release);

return rc;
}

static int
cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,
struct cifs_sb_info *cifs_sb, struct list_head *rdata_list,
Expand All @@ -3117,6 +3177,9 @@ 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;

Expand All @@ -3125,35 +3188,74 @@ 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);
if (rc)
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 %zd count %zd\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;
rdata->offset = offset;
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;
Expand All @@ -3167,9 +3269,11 @@ 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;
}

Expand Down Expand Up @@ -3225,45 +3329,62 @@ 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;
}
}

rc = cifs_send_async_read(
if (ctx->direct_io) {
/*
* Re-use rdata as this is a
* direct I/O
*/
rc = cifs_resend_rdata(
rdata,
&tmp_list, ctx);
} else {
rc = cifs_send_async_read(
rdata->offset + got_bytes,
rdata->bytes - got_bytes,
rdata->cfile, cifs_sb,
&tmp_list, ctx);

kref_put(&rdata->refcount,
cifs_uncached_readdata_release);
}

list_splice(&tmp_list, &ctx->list);

kref_put(&rdata->refcount,
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);

Expand All @@ -3281,18 +3402,28 @@ collect_uncached_read_data(struct cifs_aio_ctx *ctx)
complete(&ctx->done);
}

ssize_t cifs_user_readv(struct kiocb *iocb, struct iov_iter *to)
static ssize_t __cifs_readv(
struct kiocb *iocb, struct iov_iter *to, bool direct)
{
struct file *file = iocb->ki_filp;
ssize_t rc;
size_t len;
ssize_t total_read = 0;
loff_t offset = iocb->ki_pos;
struct file *file = iocb->ki_filp;
struct cifs_sb_info *cifs_sb;
struct cifs_tcon *tcon;
struct cifsFileInfo *cfile;
struct cifs_tcon *tcon;
ssize_t rc, total_read = 0;
loff_t offset = iocb->ki_pos;
struct cifs_aio_ctx *ctx;

/*
* iov_iter_get_pages_alloc() doesn't work with ITER_KVEC,
* fall back to data copy read path
* this could be improved by getting pages directly in ITER_KVEC
*/
if (direct && to->type & ITER_KVEC) {
cifs_dbg(FYI, "use non-direct cifs_user_readv for kvec I/O\n");
direct = false;
}

len = iov_iter_count(to);
if (!len)
return 0;
Expand All @@ -3319,14 +3450,20 @@ ssize_t cifs_user_readv(struct kiocb *iocb, struct iov_iter *to)
if (iter_is_iovec(to))
ctx->should_dirty = true;

rc = setup_aio_ctx_iter(ctx, to, READ);
if (rc) {
kref_put(&ctx->refcount, cifs_aio_ctx_release);
return rc;
if (direct) {
ctx->pos = offset;
ctx->direct_io = true;
ctx->iter = *to;
ctx->len = len;
} else {
rc = setup_aio_ctx_iter(ctx, to, READ);
if (rc) {
kref_put(&ctx->refcount, cifs_aio_ctx_release);
return rc;
}
len = ctx->len;
}

len = ctx->len;

/* grab a lock here due to read response handlers can access ctx */
mutex_lock(&ctx->aio_mutex);

Expand Down Expand Up @@ -3368,6 +3505,16 @@ ssize_t cifs_user_readv(struct kiocb *iocb, struct iov_iter *to)
return rc;
}

ssize_t cifs_direct_readv(struct kiocb *iocb, struct iov_iter *to)
{
return __cifs_readv(iocb, to, true);
}

ssize_t cifs_user_readv(struct kiocb *iocb, struct iov_iter *to)
{
return __cifs_readv(iocb, to, false);
}

ssize_t
cifs_strict_readv(struct kiocb *iocb, struct iov_iter *to)
{
Expand Down

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