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提交 06cf6f2e 编写于 作者: C Chuck Lever 提交者： Trond Myklebust
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NFS: Eliminate nfs_get_user_pages() 

Neil Brown observed that the kmalloc() in nfs_get_user_pages() is more
likely to fail if the I/O is large enough to require the allocation of more
than a single page to keep track of all the pinned pages in the user's
buffer.

Instead of tracking one large page array per dreq/iocb, track pages per
nfs_read/write_data, just like the cached I/O path does.  An array for
pages is already allocated for us by nfs_readdata_alloc() (and the write
and commit equivalents).

This is also required for adding support for vectored I/O to the NFS direct
I/O path.

The original reason to pin the user buffer and allocate all the NFS data
structures before trying to schedule I/O was to ensure all needed resources
are allocated on the client before starting to send requests.  This reduces
the chance that resource exhaustion on the client will cause a short read
or write.

On the other hand, for an application making very large application I/O
requests, this means that it will be nearly impossible for the application
to make forward progress on a resource-limited client.

Thus, moving the buffer pinning functionality into the I/O scheduling
loops should be good for scalability.  The next patch will do the same for
NFS data structure allocation.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
上级 9c93ab7d
隐藏空白更改
内联 并排
Showing with 113 addition and 94 deletion
fs/nfs/direct.c
浏览文件 @ 06cf6f2e
......@@ -73,8 +73,6 @@ struct nfs_direct_req {
struct nfs_open_context *ctx; /* file open context info */
struct kiocb * iocb; /* controlling i/o request */
struct inode * inode; /* target file of i/o */
struct page ** pages; /* pages in our buffer */
unsigned int npages; /* count of pages */
/* completion state */
atomic_t io_count; /* i/os we're waiting for */
......@@ -104,6 +102,20 @@ static inline int put_dreq(struct nfs_direct_req *dreq)
return atomic_dec_and_test(&dreq->io_count);
}
/*
* "size" is never larger than rsize or wsize.
*/
static inline int nfs_direct_count_pages(unsigned long user_addr, size_t size)
{
int page_count;
page_count = (user_addr + size + PAGE_SIZE - 1) >> PAGE_SHIFT;
page_count -= user_addr >> PAGE_SHIFT;
BUG_ON(page_count < 0);
return page_count;
}
/**
* nfs_direct_IO - NFS address space operation for direct I/O
* @rw: direction (read or write)
......@@ -143,40 +155,6 @@ static void nfs_direct_release_pages(struct page **pages, int npages)
page_cache_release(pages[i]);
}
static inline int nfs_get_user_pages(int rw, unsigned long user_addr, size_t size, struct page ***pages)
{
int result = -ENOMEM;
unsigned long page_count;
size_t array_size;
page_count = (user_addr + size + PAGE_SIZE - 1) >> PAGE_SHIFT;
page_count -= user_addr >> PAGE_SHIFT;
array_size = (page_count * sizeof(struct page *));
*pages = kmalloc(array_size, GFP_KERNEL);
if (*pages) {
down_read(&current->mm->mmap_sem);
result = get_user_pages(current, current->mm, user_addr,
page_count, (rw == READ), 0,
*pages, NULL);
up_read(&current->mm->mmap_sem);
if (result != page_count) {
/*
* If we got fewer pages than expected from
* get_user_pages(), the user buffer runs off the
* end of a mapping; return EFAULT.
*/
if (result >= 0) {
nfs_direct_release_pages(*pages, result);
result = -EFAULT;
} else
kfree(*pages);
*pages = NULL;
}
}
return result;
}
static inline struct nfs_direct_req *nfs_direct_req_alloc(void)
{
struct nfs_direct_req *dreq;
......@@ -233,13 +211,8 @@ static ssize_t nfs_direct_wait(struct nfs_direct_req *dreq)
}
/*
* We must hold a reference to all the pages in this direct read request
* until the RPCs complete. This could be long *after* we are woken up in
* nfs_direct_wait (for instance, if someone hits ^C on a slow server).
*
* In addition, synchronous I/O uses a stack-allocated iocb. Thus we
* can't trust the iocb is still valid here if this is a synchronous
* request. If the waiter is woken prematurely, the iocb is long gone.
* Synchronous I/O uses a stack-allocated iocb. Thus we can't trust
* the iocb is still valid here if this is a synchronous request.
*/
static void nfs_direct_complete(struct nfs_direct_req *dreq)
{
......@@ -297,6 +270,11 @@ static struct nfs_direct_req *nfs_direct_read_alloc(size_t nbytes, size_t rsize)
return dreq;
}
/*
* We must hold a reference to all the pages in this direct read request
* until the RPCs complete. This could be long *after* we are woken up in
* nfs_direct_wait (for instance, if someone hits ^C on a slow server).
*/
static void nfs_direct_read_result(struct rpc_task *task, void *calldata)
{
struct nfs_read_data *data = calldata;
......@@ -305,6 +283,9 @@ static void nfs_direct_read_result(struct rpc_task *task, void *calldata)
if (nfs_readpage_result(task, data) != 0)
return;
nfs_direct_dirty_pages(data->pagevec, data->npages);
nfs_direct_release_pages(data->pagevec, data->npages);
spin_lock(&dreq->lock);
if (likely(task->tk_status >= 0))
......@@ -314,11 +295,8 @@ static void nfs_direct_read_result(struct rpc_task *task, void *calldata)
spin_unlock(&dreq->lock);
if (put_dreq(dreq)) {
nfs_direct_dirty_pages(dreq->pages, dreq->npages);
nfs_direct_release_pages(dreq->pages, dreq->npages);
if (put_dreq(dreq))
nfs_direct_complete(dreq);
}
}
static const struct rpc_call_ops nfs_read_direct_ops = {
......@@ -328,21 +306,23 @@ static const struct rpc_call_ops nfs_read_direct_ops = {
/*
* For each nfs_read_data struct that was allocated on the list, dispatch
* an NFS READ operation
* an NFS READ operation. If get_user_pages() fails, we stop sending reads.
* Read length accounting is handled by nfs_direct_read_result().
* Otherwise, if no requests have been sent, just return an error.
*/
static void nfs_direct_read_schedule(struct nfs_direct_req *dreq, unsigned long user_addr, size_t count, loff_t pos)
static ssize_t nfs_direct_read_schedule(struct nfs_direct_req *dreq, unsigned long user_addr, size_t count, loff_t pos)
{
struct nfs_open_context *ctx = dreq->ctx;
struct inode *inode = ctx->dentry->d_inode;
struct list_head *list = &dreq->list;
struct page **pages = dreq->pages;
size_t rsize = NFS_SERVER(inode)->rsize;
unsigned int curpage, pgbase;
unsigned int pgbase;
int result;
ssize_t started = 0;
struct nfs_read_data *data;
curpage = 0;
pgbase = user_addr & ~PAGE_MASK;
do {
struct nfs_read_data *data;
size_t bytes;
bytes = rsize;
......@@ -353,13 +333,21 @@ static void nfs_direct_read_schedule(struct nfs_direct_req *dreq, unsigned long
data = list_entry(list->next, struct nfs_read_data, pages);
list_del_init(&data->pages);
data->npages = nfs_direct_count_pages(user_addr, bytes);
down_read(&current->mm->mmap_sem);
result = get_user_pages(current, current->mm, user_addr,
data->npages, 1, 0, data->pagevec, NULL);
up_read(&current->mm->mmap_sem);
if (unlikely(result < data->npages))
goto out_err;
data->inode = inode;
data->cred = ctx->cred;
data->args.fh = NFS_FH(inode);
data->args.context = ctx;
data->args.offset = pos;
data->args.pgbase = pgbase;
data->args.pages = &pages[curpage];
data->args.pages = data->pagevec;
data->args.count = bytes;
data->res.fattr = &data->fattr;
data->res.eof = 0;
......@@ -382,17 +370,36 @@ static void nfs_direct_read_schedule(struct nfs_direct_req *dreq, unsigned long
bytes,
(unsigned long long)data->args.offset);
started += bytes;
user_addr += bytes;
pos += bytes;
pgbase += bytes;
curpage += pgbase >> PAGE_SHIFT;
pgbase &= ~PAGE_MASK;
count -= bytes;
} while (count != 0);
BUG_ON(!list_empty(list));
return 0;
out_err:
if (result > 0)
nfs_direct_release_pages(data->pagevec, result);
list_add(&data->pages, list);
while (!list_empty(list)) {
data = list_entry(list->next, struct nfs_read_data, pages);
list_del(&data->pages);
nfs_readdata_free(data);
if (put_dreq(dreq))
nfs_direct_complete(dreq);
}
if (started)
return 0;
return result < 0 ? (ssize_t) result : -EFAULT;
}
static ssize_t nfs_direct_read(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos, struct page **pages, unsigned int nr_pages)
static ssize_t nfs_direct_read(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos)
{
ssize_t result;
sigset_t oldset;
......@@ -404,8 +411,6 @@ static ssize_t nfs_direct_read(struct kiocb *iocb, unsigned long user_addr, size
if (!dreq)
return -ENOMEM;
dreq->pages = pages;
dreq->npages = nr_pages;
dreq->inode = inode;
dreq->ctx = get_nfs_open_context((struct nfs_open_context *)iocb->ki_filp->private_data);
if (!is_sync_kiocb(iocb))
......@@ -413,8 +418,9 @@ static ssize_t nfs_direct_read(struct kiocb *iocb, unsigned long user_addr, size
nfs_add_stats(inode, NFSIOS_DIRECTREADBYTES, count);
rpc_clnt_sigmask(clnt, &oldset);
nfs_direct_read_schedule(dreq, user_addr, count, pos);
result = nfs_direct_wait(dreq);
result = nfs_direct_read_schedule(dreq, user_addr, count, pos);
if (!result)
result = nfs_direct_wait(dreq);
rpc_clnt_sigunmask(clnt, &oldset);
return result;
......@@ -426,9 +432,9 @@ static void nfs_direct_free_writedata(struct nfs_direct_req *dreq)
while (!list_empty(&dreq->list)) {
struct nfs_write_data *data = list_entry(dreq->list.next, struct nfs_write_data, pages);
list_del(&data->pages);
nfs_direct_release_pages(data->pagevec, data->npages);
nfs_writedata_release(data);
}
nfs_direct_release_pages(dreq->pages, dreq->npages);
}
#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
......@@ -672,21 +678,23 @@ static const struct rpc_call_ops nfs_write_direct_ops = {
/*
* For each nfs_write_data struct that was allocated on the list, dispatch
* an NFS WRITE operation
* an NFS WRITE operation. If get_user_pages() fails, we stop sending writes.
* Write length accounting is handled by nfs_direct_write_result().
* Otherwise, if no requests have been sent, just return an error.
*/
static void nfs_direct_write_schedule(struct nfs_direct_req *dreq, unsigned long user_addr, size_t count, loff_t pos, int sync)
static ssize_t nfs_direct_write_schedule(struct nfs_direct_req *dreq, unsigned long user_addr, size_t count, loff_t pos, int sync)
{
struct nfs_open_context *ctx = dreq->ctx;
struct inode *inode = ctx->dentry->d_inode;
struct list_head *list = &dreq->list;
struct page **pages = dreq->pages;
size_t wsize = NFS_SERVER(inode)->wsize;
unsigned int curpage, pgbase;
unsigned int pgbase;
int result;
ssize_t started = 0;
struct nfs_write_data *data;
curpage = 0;
pgbase = user_addr & ~PAGE_MASK;
do {
struct nfs_write_data *data;
size_t bytes;
bytes = wsize;
......@@ -695,6 +703,15 @@ static void nfs_direct_write_schedule(struct nfs_direct_req *dreq, unsigned long
BUG_ON(list_empty(list));
data = list_entry(list->next, struct nfs_write_data, pages);
data->npages = nfs_direct_count_pages(user_addr, bytes);
down_read(&current->mm->mmap_sem);
result = get_user_pages(current, current->mm, user_addr,
data->npages, 0, 0, data->pagevec, NULL);
up_read(&current->mm->mmap_sem);
if (unlikely(result < data->npages))
goto out_err;
list_move_tail(&data->pages, &dreq->rewrite_list);
data->inode = inode;
......@@ -703,7 +720,7 @@ static void nfs_direct_write_schedule(struct nfs_direct_req *dreq, unsigned long
data->args.context = ctx;
data->args.offset = pos;
data->args.pgbase = pgbase;
data->args.pages = &pages[curpage];
data->args.pages = data->pagevec;
data->args.count = bytes;
data->res.fattr = &data->fattr;
data->res.count = bytes;
......@@ -727,17 +744,36 @@ static void nfs_direct_write_schedule(struct nfs_direct_req *dreq, unsigned long
bytes,
(unsigned long long)data->args.offset);
started += bytes;
user_addr += bytes;
pos += bytes;
pgbase += bytes;
curpage += pgbase >> PAGE_SHIFT;
pgbase &= ~PAGE_MASK;
count -= bytes;
} while (count != 0);
BUG_ON(!list_empty(list));
return 0;
out_err:
if (result > 0)
nfs_direct_release_pages(data->pagevec, result);
list_add(&data->pages, list);
while (!list_empty(list)) {
data = list_entry(list->next, struct nfs_write_data, pages);
list_del(&data->pages);
nfs_writedata_free(data);
if (put_dreq(dreq))
nfs_direct_write_complete(dreq, inode);
}
if (started)
return 0;
return result < 0 ? (ssize_t) result : -EFAULT;
}
static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos, struct page **pages, int nr_pages)
static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos)
{
ssize_t result;
sigset_t oldset;
......@@ -753,8 +789,6 @@ static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, siz
if (dreq->commit_data == NULL || count < wsize)
sync = FLUSH_STABLE;
dreq->pages = pages;
dreq->npages = nr_pages;
dreq->inode = inode;
dreq->ctx = get_nfs_open_context((struct nfs_open_context *)iocb->ki_filp->private_data);
if (!is_sync_kiocb(iocb))
......@@ -765,8 +799,9 @@ static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, siz
nfs_begin_data_update(inode);
rpc_clnt_sigmask(clnt, &oldset);
nfs_direct_write_schedule(dreq, user_addr, count, pos, sync);
result = nfs_direct_wait(dreq);
result = nfs_direct_write_schedule(dreq, user_addr, count, pos, sync);
if (!result)
result = nfs_direct_wait(dreq);
rpc_clnt_sigunmask(clnt, &oldset);
return result;
......@@ -796,8 +831,6 @@ static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, siz
ssize_t nfs_file_direct_read(struct kiocb *iocb, char __user *buf, size_t count, loff_t pos)
{
ssize_t retval = -EINVAL;
int page_count;
struct page **pages;
struct file *file = iocb->ki_filp;
struct address_space *mapping = file->f_mapping;
......@@ -819,14 +852,7 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, char __user *buf, size_t count,
if (retval)
goto out;
retval = nfs_get_user_pages(READ, (unsigned long) buf,
count, &pages);
if (retval < 0)
goto out;
page_count = retval;
retval = nfs_direct_read(iocb, (unsigned long) buf, count, pos,
pages, page_count);
retval = nfs_direct_read(iocb, (unsigned long) buf, count, pos);
if (retval > 0)
iocb->ki_pos = pos + retval;
......@@ -862,8 +888,6 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, char __user *buf, size_t count,
ssize_t nfs_file_direct_write(struct kiocb *iocb, const char __user *buf, size_t count, loff_t pos)
{
ssize_t retval;
int page_count;
struct page **pages;
struct file *file = iocb->ki_filp;
struct address_space *mapping = file->f_mapping;
......@@ -891,14 +915,7 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, const char __user *buf, size_t
if (retval)
goto out;
retval = nfs_get_user_pages(WRITE, (unsigned long) buf,
count, &pages);
if (retval < 0)
goto out;
page_count = retval;
retval = nfs_direct_write(iocb, (unsigned long) buf, count,
pos, pages, page_count);
retval = nfs_direct_write(iocb, (unsigned long) buf, count, pos);
/*
* XXX: nfs_end_data_update() already ensures this file's
......
include/linux/nfs_xdr.h
浏览文件 @ 06cf6f2e
......@@ -729,6 +729,7 @@ struct nfs_read_data {
struct list_head pages; /* Coalesced read requests */
struct nfs_page *req; /* multi ops per nfs_page */
struct page **pagevec;
unsigned int npages; /* active pages in pagevec */
struct nfs_readargs args;
struct nfs_readres res;
#ifdef CONFIG_NFS_V4
......@@ -747,6 +748,7 @@ struct nfs_write_data {
struct list_head pages; /* Coalesced requests we wish to flush */
struct nfs_page *req; /* multi ops per nfs_page */
struct page **pagevec;
unsigned int npages; /* active pages in pagevec */
struct nfs_writeargs args; /* argument struct */
struct nfs_writeres res; /* result struct */
#ifdef CONFIG_NFS_V4
......
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