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Subject[PATCH 08/30] ocfs2: Readpages support
Date
Add ->readpages support to Ocfs2. This is rather trivial - all it required
is a small update to ocfs2_get_block (for mapping full extents via b_size)
and an ocfs2_readpages() function which partially mirrors ocfs2_readpage().

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
---
fs/ocfs2/aops.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 66 insertions(+), 2 deletions(-)

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index ac8c390..2a0eaac 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -26,6 +26,7 @@
#include <asm/byteorder.h>
#include <linux/swap.h>
#include <linux/pipe_fs_i.h>
+#include <linux/mpage.h>

#define MLOG_MASK_PREFIX ML_FILE_IO
#include <cluster/masklog.h>
@@ -139,7 +140,8 @@ static int ocfs2_get_block(struct inode *inode, sector_t iblock,
{
int err = 0;
unsigned int ext_flags;
- u64 p_blkno, past_eof;
+ u64 max_blocks = bh_result->b_size >> inode->i_blkbits;
+ u64 p_blkno, count, past_eof;
struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

mlog_entry("(0x%p, %llu, 0x%p, %d)\n", inode,
@@ -155,7 +157,7 @@ static int ocfs2_get_block(struct inode *inode, sector_t iblock,
goto bail;
}

- err = ocfs2_extent_map_get_blocks(inode, iblock, &p_blkno, NULL,
+ err = ocfs2_extent_map_get_blocks(inode, iblock, &p_blkno, &count,
&ext_flags);
if (err) {
mlog(ML_ERROR, "Error %d from get_blocks(0x%p, %llu, 1, "
@@ -164,6 +166,9 @@ static int ocfs2_get_block(struct inode *inode, sector_t iblock,
goto bail;
}

+ if (max_blocks < count)
+ count = max_blocks;
+
/*
* ocfs2 never allocates in this function - the only time we
* need to use BH_New is when we're extending i_size on a file
@@ -178,6 +183,8 @@ static int ocfs2_get_block(struct inode *inode, sector_t iblock,
if (p_blkno && !(ext_flags & OCFS2_EXT_UNWRITTEN))
map_bh(bh_result, inode->i_sb, p_blkno);

+ bh_result->b_size = count << inode->i_blkbits;
+
if (!ocfs2_sparse_alloc(osb)) {
if (p_blkno == 0) {
err = -EIO;
@@ -322,6 +329,62 @@ out:
return ret;
}

+/*
+ * This is used only for read-ahead. Failures or difficult to handle
+ * siutations are safe to ignore.
+ *
+ * Right now, we don't bother with BH_Boundary - in-inode extent lists
+ * are quite large (243 extents on 4k blocks), so most inodes don't
+ * grow out to a tree. If need be, detecting boundary extents could
+ * trivially be added in a future version of ocfs2_get_block().
+ */
+static int ocfs2_readpages(struct file *filp, struct address_space *mapping,
+ struct list_head *pages, unsigned nr_pages)
+{
+ int ret, err = -EIO;
+ struct inode *inode = mapping->host;
+ struct ocfs2_inode_info *oi = OCFS2_I(inode);
+ loff_t start;
+ struct page *last;
+
+ /*
+ * Use the nonblocking flag for the dlm code to avoid page
+ * lock inversion, but don't bother with retrying.
+ */
+ ret = ocfs2_inode_lock_full(inode, NULL, 0, OCFS2_LOCK_NONBLOCK);
+ if (ret)
+ return err;
+
+ if (down_read_trylock(&oi->ip_alloc_sem) == 0) {
+ ocfs2_inode_unlock(inode, 0);
+ return err;
+ }
+
+ /*
+ * Don't bother with inline-data. There isn't anything
+ * to read-ahead in that case anyway...
+ */
+ if (oi->ip_dyn_features & OCFS2_INLINE_DATA_FL)
+ goto out_unlock;
+
+ /*
+ * Check whether a remote node truncated this file - we just
+ * drop out in that case as it's not worth handling here.
+ */
+ last = list_entry(pages->prev, struct page, lru);
+ start = (loff_t)last->index << PAGE_CACHE_SHIFT;
+ if (start >= i_size_read(inode))
+ goto out_unlock;
+
+ err = mpage_readpages(mapping, pages, nr_pages, ocfs2_get_block);
+
+out_unlock:
+ up_read(&oi->ip_alloc_sem);
+ ocfs2_inode_unlock(inode, 0);
+
+ return err;
+}
+
/* Note: Because we don't support holes, our allocation has
* already happened (allocation writes zeros to the file data)
* so we don't have to worry about ordered writes in
@@ -1877,6 +1940,7 @@ static int ocfs2_write_end(struct file *file, struct address_space *mapping,

const struct address_space_operations ocfs2_aops = {
.readpage = ocfs2_readpage,
+ .readpages = ocfs2_readpages,
.writepage = ocfs2_writepage,
.write_begin = ocfs2_write_begin,
.write_end = ocfs2_write_end,
--
1.5.3.6


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