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cifs: convert cifs_readpages to use async reads
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Now that we have code in place to do asynchronous reads, convert
cifs_readpages to use it. The new cifs_readpages walks the page_list
that gets passed in, locks and adds the pages to the pagecache and
sets up cifs_readdata to handle the reads.

The rest is handled by the cifs_async_readv infrastructure.

Reviewed-and-Tested-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
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Jeff Layton committed Oct 19, 2011
1 parent e28bc5b commit 690c5e3
Showing 1 changed file with 113 additions and 168 deletions.
281 changes: 113 additions & 168 deletions fs/cifs/file.c
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@
#include <linux/delay.h>
#include <linux/mount.h>
#include <linux/slab.h>
#include <linux/swap.h>
#include <asm/div64.h>
#include "cifsfs.h"
#include "cifspdu.h"
Expand Down Expand Up @@ -2000,82 +2001,24 @@ int cifs_file_mmap(struct file *file, struct vm_area_struct *vma)
return rc;
}


static void cifs_copy_cache_pages(struct address_space *mapping,
struct list_head *pages, int bytes_read, char *data)
{
struct page *page;
char *target;

while (bytes_read > 0) {
if (list_empty(pages))
break;

page = list_entry(pages->prev, struct page, lru);
list_del(&page->lru);

if (add_to_page_cache_lru(page, mapping, page->index,
GFP_KERNEL)) {
page_cache_release(page);
cFYI(1, "Add page cache failed");
data += PAGE_CACHE_SIZE;
bytes_read -= PAGE_CACHE_SIZE;
continue;
}
page_cache_release(page);

target = kmap_atomic(page, KM_USER0);

if (PAGE_CACHE_SIZE > bytes_read) {
memcpy(target, data, bytes_read);
/* zero the tail end of this partial page */
memset(target + bytes_read, 0,
PAGE_CACHE_SIZE - bytes_read);
bytes_read = 0;
} else {
memcpy(target, data, PAGE_CACHE_SIZE);
bytes_read -= PAGE_CACHE_SIZE;
}
kunmap_atomic(target, KM_USER0);

flush_dcache_page(page);
SetPageUptodate(page);
unlock_page(page);
data += PAGE_CACHE_SIZE;

/* add page to FS-Cache */
cifs_readpage_to_fscache(mapping->host, page);
}
return;
}

static int cifs_readpages(struct file *file, struct address_space *mapping,
struct list_head *page_list, unsigned num_pages)
{
int rc = -EACCES;
int xid;
loff_t offset;
struct page *page;
struct cifs_sb_info *cifs_sb;
struct cifs_tcon *pTcon;
unsigned int bytes_read = 0;
unsigned int read_size, i;
char *smb_read_data = NULL;
struct smb_com_read_rsp *pSMBr;
struct cifsFileInfo *open_file;
struct cifs_io_parms io_parms;
int buf_type = CIFS_NO_BUFFER;
__u32 pid;
int rc;
struct list_head tmplist;
struct cifsFileInfo *open_file = file->private_data;
struct cifs_sb_info *cifs_sb = CIFS_SB(file->f_path.dentry->d_sb);
unsigned int rsize = cifs_sb->rsize;
pid_t pid;

xid = GetXid();
if (file->private_data == NULL) {
rc = -EBADF;
FreeXid(xid);
return rc;
}
open_file = file->private_data;
cifs_sb = CIFS_SB(file->f_path.dentry->d_sb);
pTcon = tlink_tcon(open_file->tlink);
/*
* Give up immediately if rsize is too small to read an entire page.
* The VFS will fall back to readpage. We should never reach this
* point however since we set ra_pages to 0 when the rsize is smaller
* than a cache page.
*/
if (unlikely(rsize < PAGE_CACHE_SIZE))
return 0;

/*
* Reads as many pages as possible from fscache. Returns -ENOBUFS
Expand All @@ -2084,125 +2027,127 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
rc = cifs_readpages_from_fscache(mapping->host, mapping, page_list,
&num_pages);
if (rc == 0)
goto read_complete;
return rc;

cFYI(DBG2, "rpages: num pages %d", num_pages);
if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_RWPIDFORWARD)
pid = open_file->pid;
else
pid = current->tgid;

for (i = 0; i < num_pages; ) {
unsigned contig_pages;
struct page *tmp_page;
unsigned long expected_index;
rc = 0;
INIT_LIST_HEAD(&tmplist);

if (list_empty(page_list))
break;
cFYI(1, "%s: file=%p mapping=%p num_pages=%u", __func__, file,
mapping, num_pages);

/*
* Start with the page at end of list and move it to private
* list. Do the same with any following pages until we hit
* the rsize limit, hit an index discontinuity, or run out of
* pages. Issue the async read and then start the loop again
* until the list is empty.
*
* Note that list order is important. The page_list is in
* the order of declining indexes. When we put the pages in
* the rdata->pages, then we want them in increasing order.
*/
while (!list_empty(page_list)) {
unsigned int bytes = PAGE_CACHE_SIZE;
unsigned int expected_index;
unsigned int nr_pages = 1;
loff_t offset;
struct page *page, *tpage;
struct cifs_readdata *rdata;

page = list_entry(page_list->prev, struct page, lru);

/*
* Lock the page and put it in the cache. Since no one else
* should have access to this page, we're safe to simply set
* PG_locked without checking it first.
*/
__set_page_locked(page);
rc = add_to_page_cache_locked(page, mapping,
page->index, GFP_KERNEL);

/* give up if we can't stick it in the cache */
if (rc) {
__clear_page_locked(page);
break;
}

/* move first page to the tmplist */
offset = (loff_t)page->index << PAGE_CACHE_SHIFT;
list_move_tail(&page->lru, &tmplist);

/* now try and add more pages onto the request */
expected_index = page->index + 1;
list_for_each_entry_safe_reverse(page, tpage, page_list, lru) {
/* discontinuity ? */
if (page->index != expected_index)
break;

/* would this page push the read over the rsize? */
if (bytes + PAGE_CACHE_SIZE > rsize)
break;

/* count adjacent pages that we will read into */
contig_pages = 0;
expected_index =
list_entry(page_list->prev, struct page, lru)->index;
list_for_each_entry_reverse(tmp_page, page_list, lru) {
if (tmp_page->index == expected_index) {
contig_pages++;
expected_index++;
} else
__set_page_locked(page);
if (add_to_page_cache_locked(page, mapping,
page->index, GFP_KERNEL)) {
__clear_page_locked(page);
break;
}
list_move_tail(&page->lru, &tmplist);
bytes += PAGE_CACHE_SIZE;
expected_index++;
nr_pages++;
}
if (contig_pages + i > num_pages)
contig_pages = num_pages - i;

/* for reads over a certain size could initiate async
read ahead */

read_size = contig_pages * PAGE_CACHE_SIZE;
/* Read size needs to be in multiples of one page */
read_size = min_t(const unsigned int, read_size,
cifs_sb->rsize & PAGE_CACHE_MASK);
cFYI(DBG2, "rpages: read size 0x%x contiguous pages %d",
read_size, contig_pages);
rc = -EAGAIN;
while (rc == -EAGAIN) {

rdata = cifs_readdata_alloc(nr_pages);
if (!rdata) {
/* best to give up if we're out of mem */
list_for_each_entry_safe(page, tpage, &tmplist, lru) {
list_del(&page->lru);
lru_cache_add_file(page);
unlock_page(page);
page_cache_release(page);
}
rc = -ENOMEM;
break;
}

spin_lock(&cifs_file_list_lock);
cifsFileInfo_get(open_file);
spin_unlock(&cifs_file_list_lock);
rdata->cfile = open_file;
rdata->mapping = mapping;
rdata->offset = offset;
rdata->bytes = bytes;
rdata->pid = pid;
list_splice_init(&tmplist, &rdata->pages);

do {
if (open_file->invalidHandle) {
rc = cifs_reopen_file(open_file, true);
if (rc != 0)
break;
continue;
}
io_parms.netfid = open_file->netfid;
io_parms.pid = pid;
io_parms.tcon = pTcon;
io_parms.offset = offset;
io_parms.length = read_size;
rc = CIFSSMBRead(xid, &io_parms, &bytes_read,
&smb_read_data, &buf_type);
/* BB more RC checks ? */
if (rc == -EAGAIN) {
if (smb_read_data) {
if (buf_type == CIFS_SMALL_BUFFER)
cifs_small_buf_release(smb_read_data);
else if (buf_type == CIFS_LARGE_BUFFER)
cifs_buf_release(smb_read_data);
smb_read_data = NULL;
}
}
}
if ((rc < 0) || (smb_read_data == NULL)) {
cFYI(1, "Read error in readpages: %d", rc);
break;
} else if (bytes_read > 0) {
task_io_account_read(bytes_read);
pSMBr = (struct smb_com_read_rsp *)smb_read_data;
cifs_copy_cache_pages(mapping, page_list, bytes_read,
smb_read_data + 4 /* RFC1001 hdr */ +
le16_to_cpu(pSMBr->DataOffset));

i += bytes_read >> PAGE_CACHE_SHIFT;
cifs_stats_bytes_read(pTcon, bytes_read);
if ((bytes_read & PAGE_CACHE_MASK) != bytes_read) {
i++; /* account for partial page */

/* server copy of file can have smaller size
than client */
/* BB do we need to verify this common case ?
this case is ok - if we are at server EOF
we will hit it on next read */
rc = cifs_async_readv(rdata);
} while (rc == -EAGAIN);

/* break; */
if (rc != 0) {
list_for_each_entry_safe(page, tpage, &rdata->pages,
lru) {
list_del(&page->lru);
lru_cache_add_file(page);
unlock_page(page);
page_cache_release(page);
}
} else {
cFYI(1, "No bytes read (%d) at offset %lld . "
"Cleaning remaining pages from readahead list",
bytes_read, offset);
/* BB turn off caching and do new lookup on
file size at server? */
cifs_readdata_free(rdata);
break;
}
if (smb_read_data) {
if (buf_type == CIFS_SMALL_BUFFER)
cifs_small_buf_release(smb_read_data);
else if (buf_type == CIFS_LARGE_BUFFER)
cifs_buf_release(smb_read_data);
smb_read_data = NULL;
}
bytes_read = 0;
}

/* need to free smb_read_data buf before exit */
if (smb_read_data) {
if (buf_type == CIFS_SMALL_BUFFER)
cifs_small_buf_release(smb_read_data);
else if (buf_type == CIFS_LARGE_BUFFER)
cifs_buf_release(smb_read_data);
smb_read_data = NULL;
}

read_complete:
FreeXid(xid);
return rc;
}

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