[GFS2] Readpages support
This adds readpages support (and also corrects a small bug in
the readpage error path at the same time). Hopefully this will
improve performance by allowing GFS to submit larger lumps of
I/O at a time.
In order to simplify the setting of BH_Boundary, it currently gets
set when we hit the end of a indirect pointer block. There is
always a boundary at this point with the current allocation code.
It doesn't get all the boundaries right though, so there is still
room for improvement in this.
See comments in fs/gfs2/ops_address.c for further information about
readpages with GFS2.
Signed-off-by: Steven Whitehouse
diff --git a/fs/gfs2/ops_address.c b/fs/gfs2/ops_address.c
index afcc12a..d89179b 100644
--- a/fs/gfs2/ops_address.c
+++ b/fs/gfs2/ops_address.c
@@ -13,6 +13,7 @@
#include <linux/completion.h>
#include <linux/buffer_head.h>
#include <linux/pagemap.h>
+#include <linux/pagevec.h>
#include <linux/mpage.h>
#include <linux/fs.h>
#include <linux/gfs2_ondisk.h>
@@ -47,12 +48,12 @@
int gfs2_get_block(struct inode *inode, sector_t lblock,
struct buffer_head *bh_result, int create)
{
- struct gfs2_inode *ip = inode->u.generic_ip;
int new = create;
uint64_t dblock;
int error;
+ int boundary;
- error = gfs2_block_map(ip, lblock, &new, &dblock, NULL);
+ error = gfs2_block_map(inode, lblock, &new, &dblock, &boundary);
if (error)
return error;
@@ -62,6 +63,8 @@
map_bh(bh_result, inode->i_sb, dblock);
if (new)
set_buffer_new(bh_result);
+ if (boundary)
+ set_buffer_boundary(bh_result);
return 0;
}
@@ -83,8 +86,9 @@
int new = 0;
uint64_t dblock;
int error;
+ int boundary;
- error = gfs2_block_map(ip, lblock, &new, &dblock, NULL);
+ error = gfs2_block_map(inode, lblock, &new, &dblock, &boundary);
if (error)
return error;
@@ -92,6 +96,8 @@
map_bh(bh_result, inode->i_sb, dblock);
else if (gfs2_assert_withdraw(ip->i_sbd, !create))
error = -EIO;
+ if (boundary)
+ set_buffer_boundary(bh_result);
return error;
}
@@ -151,6 +157,19 @@
return 0;
}
+static int zero_readpage(struct page *page)
+{
+ void *kaddr;
+
+ kaddr = kmap_atomic(page, KM_USER0);
+ memset(kaddr, 0, PAGE_CACHE_SIZE);
+ kunmap_atomic(page, KM_USER0);
+
+ SetPageUptodate(page);
+
+ return 0;
+}
+
/**
* stuffed_readpage - Fill in a Linux page with stuffed file data
* @ip: the inode
@@ -165,17 +184,18 @@
void *kaddr;
int error;
+ /* Only the first page of a stuffed file might contain data */
+ if (unlikely(page->index))
+ return zero_readpage(page);
+
error = gfs2_meta_inode_buffer(ip, &dibh);
if (error)
return error;
kaddr = kmap_atomic(page, KM_USER0);
- memcpy((char *)kaddr,
- dibh->b_data + sizeof(struct gfs2_dinode),
+ memcpy(kaddr, dibh->b_data + sizeof(struct gfs2_dinode),
ip->i_di.di_size);
- memset((char *)kaddr + ip->i_di.di_size,
- 0,
- PAGE_CACHE_SIZE - ip->i_di.di_size);
+ memset(kaddr + ip->i_di.di_size, 0, PAGE_CACHE_SIZE - ip->i_di.di_size);
kunmap_atomic(page, KM_USER0);
brelse(dibh);
@@ -185,19 +205,6 @@
return 0;
}
-static int zero_readpage(struct page *page)
-{
- void *kaddr;
-
- kaddr = kmap_atomic(page, KM_USER0);
- memset(kaddr, 0, PAGE_CACHE_SIZE);
- kunmap_atomic(page, KM_USER0);
-
- SetPageUptodate(page);
- unlock_page(page);
-
- return 0;
-}
/**
* gfs2_readpage - readpage with locking
@@ -215,19 +222,16 @@
struct gfs2_holder gh;
int error;
- if (file != &gfs2_internal_file_sentinal) {
+ if (likely(file != &gfs2_internal_file_sentinal)) {
gfs2_holder_init(ip->i_gl, LM_ST_SHARED, GL_ATIME|GL_AOP, &gh);
error = gfs2_glock_nq_m_atime(1, &gh);
- if (error)
+ if (unlikely(error))
goto out_unlock;
}
if (gfs2_is_stuffed(ip)) {
- if (!page->index) {
- error = stuffed_readpage(ip, page);
- unlock_page(page);
- } else
- error = zero_readpage(page);
+ error = stuffed_readpage(ip, page);
+ unlock_page(page);
} else
error = mpage_readpage(page, gfs2_get_block);
@@ -242,6 +246,90 @@
return error;
out_unlock:
unlock_page(page);
+ if (file != &gfs2_internal_file_sentinal)
+ gfs2_holder_uninit(&gh);
+ goto out;
+}
+
+#define list_to_page(head) (list_entry((head)->prev, struct page, lru))
+
+/**
+ * gfs2_readpages - Read a bunch of pages at once
+ *
+ * Some notes:
+ * 1. This is only for readahead, so we can simply ignore any things
+ * which are slightly inconvenient (such as locking conflicts between
+ * the page lock and the glock) and return having done no I/O. Its
+ * obviously not something we'd want to do on too regular a basis.
+ * Any I/O we ignore at this time will be done via readpage later.
+ * 2. We have to handle stuffed files here too.
+ * 3. mpage_readpages() does most of the heavy lifting in the common case.
+ * 4. gfs2_get_block() is relied upon to set BH_Boundary in the right places.
+ * 5. We use LM_FLAG_TRY_1CB here, effectively we then have lock-ahead as
+ * well as read-ahead.
+ */
+static int gfs2_readpages(struct file *file, struct address_space *mapping,
+ struct list_head *pages, unsigned nr_pages)
+{
+ struct inode *inode = mapping->host;
+ struct gfs2_inode *ip = inode->u.generic_ip;
+ struct gfs2_sbd *sdp = ip->i_sbd;
+ struct gfs2_holder gh;
+ unsigned page_idx;
+ int ret;
+
+ if (likely(file != &gfs2_internal_file_sentinal)) {
+ gfs2_holder_init(ip->i_gl, LM_ST_SHARED,
+ LM_FLAG_TRY_1CB|GL_ATIME|GL_AOP, &gh);
+ ret = gfs2_glock_nq_m_atime(1, &gh);
+ if (ret == GLR_TRYFAILED)
+ goto out_noerror;
+ if (unlikely(ret))
+ goto out_unlock;
+ }
+
+ if (gfs2_is_stuffed(ip)) {
+ struct pagevec lru_pvec;
+ pagevec_init(&lru_pvec, 0);
+ for (page_idx = 0; page_idx < nr_pages; page_idx++) {
+ struct page *page = list_to_page(pages);
+ list_del(&page->lru);
+ if (!add_to_page_cache(page, mapping,
+ page->index, GFP_KERNEL)) {
+ ret = stuffed_readpage(ip, page);
+ unlock_page(page);
+ if (!pagevec_add(&lru_pvec, page))
+ __pagevec_lru_add(&lru_pvec);
+ }
+ page_cache_release(page);
+ }
+ pagevec_lru_add(&lru_pvec);
+ ret = 0;
+ } else {
+ /* What we really want to do .... */
+ ret = mpage_readpages(mapping, pages, nr_pages, gfs2_get_block);
+ }
+
+ if (likely(file != &gfs2_internal_file_sentinal)) {
+ gfs2_glock_dq_m(1, &gh);
+ gfs2_holder_uninit(&gh);
+ }
+out:
+ if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags)))
+ ret = -EIO;
+ return ret;
+out_noerror:
+ ret = 0;
+out_unlock:
+ /* unlock all pages, we can't do any I/O right now */
+ for (page_idx = 0; page_idx < nr_pages; page_idx++) {
+ struct page *page = list_to_page(pages);
+ list_del(&page->lru);
+ unlock_page(page);
+ page_cache_release(page);
+ }
+ if (likely(file != &gfs2_internal_file_sentinal))
+ gfs2_holder_uninit(&gh);
goto out;
}
@@ -572,6 +660,7 @@
struct address_space_operations gfs2_file_aops = {
.writepage = gfs2_writepage,
.readpage = gfs2_readpage,
+ .readpages = gfs2_readpages,
.sync_page = block_sync_page,
.prepare_write = gfs2_prepare_write,
.commit_write = gfs2_commit_write,