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Old 01-21-2008, 08:21 AM
 
Default Clean up internal read function

From: Steven Whitehouse <swhiteho@redhat.com>

As requested by Christoph, this patch cleans up GFS2's internal
read function so that it no longer uses the do_generic_mapping_read
function. This function is obsolete and GFS2 is the last user of it.

As a side effect the internal read code gets smaller and easier
to read and gfs2_readpage is split into two. One function has the locking
and the other function has the rest of the logic.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>

diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 5f6dc32..ad0fe37 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -31,7 +31,6 @@
#include "log.h"
#include "meta_io.h"
#include "ops_address.h"
-#include "ops_file.h"
#include "ops_inode.h"
#include "quota.h"
#include "rgrp.h"
diff --git a/fs/gfs2/ops_address.c b/fs/gfs2/ops_address.c
index 9679f8b..9bb24b1 100644
--- a/fs/gfs2/ops_address.c
+++ b/fs/gfs2/ops_address.c
@@ -20,6 +20,7 @@
#include <linux/swap.h>
#include <linux/gfs2_ondisk.h>
#include <linux/lm_interface.h>
+#include <linux/swap.h>

#include "gfs2.h"
#include "incore.h"
@@ -32,7 +33,6 @@
#include "quota.h"
#include "trans.h"
#include "rgrp.h"
-#include "ops_file.h"
#include "super.h"
#include "util.h"
#include "glops.h"
@@ -231,62 +231,115 @@ static int stuffed_readpage(struct gfs2_inode *ip, struct page *page)


/**
- * gfs2_readpage - readpage with locking
- * @file: The file to read a page for. N.B. This may be NULL if we are
- * reading an internal file.
+ * __gfs2_readpage - readpage
+ * @file: The file to read a page for
* @page: The page to read
*
- * Returns: errno
+ * This is the core of gfs2's readpage. Its used by the internal file
+ * reading code as in that case we already hold the glock. Also its
+ * called by gfs2_readpage() once the required lock has been granted.
+ *
*/

-static int gfs2_readpage(struct file *file, struct page *page)
+static int __gfs2_readpage(void *file, struct page *page)
{
struct gfs2_inode *ip = GFS2_I(page->mapping->host);
struct gfs2_sbd *sdp = GFS2_SB(page->mapping->host);
- struct gfs2_file *gf = NULL;
- struct gfs2_holder gh;
int error;
- int do_unlock = 0;
-
- if (likely(file != &gfs2_internal_file_sentinel)) {
- if (file) {
- gf = file->private_data;
- if (test_bit(GFF_EXLOCK, &gf->f_flags))
- /* gfs2_sharewrite_fault has grabbed the ip->i_gl already */
- goto skip_lock;
- }
- gfs2_holder_init(ip->i_gl, LM_ST_SHARED, GL_ATIME|LM_FLAG_TRY_1CB, &gh);
- do_unlock = 1;
- error = gfs2_glock_nq_atime(&gh);
- if (unlikely(error))
- goto out_unlock;
- }

-skip_lock:
if (gfs2_is_stuffed(ip)) {
error = stuffed_readpage(ip, page);
unlock_page(page);
- } else
+ } else {
error = mpage_readpage(page, gfs2_get_block);
+ }

if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags)))
- error = -EIO;
+ return -EIO;

- if (do_unlock) {
- gfs2_glock_dq_m(1, &gh);
- gfs2_holder_uninit(&gh);
+ return error;
+}
+
+/**
+ * gfs2_readpage - read a page of a file
+ * @file: The file to read
+ * @page: The page of the file
+ *
+ * This deals with the locking required. If the GFF_EXLOCK flags is set
+ * then we already hold the glock (due to page fault) and thus we call
+ * __gfs2_readpage() directly. Otherwise we use a trylock in order to
+ * avoid the page lock / glock ordering problems returning AOP_TRUNCATED_PAGE
+ * in the event that we are unable to get the lock.
+ */
+
+static int gfs2_readpage(struct file *file, struct page *page)
+{
+ struct gfs2_inode *ip = GFS2_I(page->mapping->host);
+ struct gfs2_holder gh;
+ int error;
+
+ if (file) {
+ struct gfs2_file *gf = file->private_data;
+ if (test_bit(GFF_EXLOCK, &gf->f_flags))
+ return __gfs2_readpage(file, page);
}
+
+ gfs2_holder_init(ip->i_gl, LM_ST_SHARED, GL_ATIME|LM_FLAG_TRY_1CB, &gh);
+ error = gfs2_glock_nq_atime(&gh);
+ if (unlikely(error)) {
+ unlock_page(page);
+ goto out;
+ }
+ error = __gfs2_readpage(file, page);
+ gfs2_glock_dq(&gh);
out:
- return error;
-out_unlock:
- unlock_page(page);
+ gfs2_holder_uninit(&gh);
if (error == GLR_TRYFAILED) {
- error = AOP_TRUNCATED_PAGE;
yield();
+ return AOP_TRUNCATED_PAGE;
}
- if (do_unlock)
- gfs2_holder_uninit(&gh);
- goto out;
+ return error;
+}
+
+/**
+ * gfs2_internal_read - read an internal file
+ * @ip: The gfs2 inode
+ * @ra_state: The readahead state (or NULL for no readahead)
+ * @buf: The buffer to fill
+ * @pos: The file position
+ * @size: The amount to read
+ *
+ */
+
+int gfs2_internal_read(struct gfs2_inode *ip, struct file_ra_state *ra_state,
+ char *buf, loff_t *pos, unsigned size)
+{
+ struct address_space *mapping = ip->i_inode.i_mapping;
+ unsigned long index = *pos / PAGE_CACHE_SIZE;
+ unsigned offset = *pos & (PAGE_CACHE_SIZE - 1);
+ unsigned copied = 0;
+ unsigned amt;
+ struct page *page;
+ void *p;
+
+ do {
+ amt = size - copied;
+ if (offset + size > PAGE_CACHE_SIZE)
+ amt = PAGE_CACHE_SIZE - offset;
+ page = read_cache_page(mapping, index, __gfs2_readpage, NULL);
+ if (IS_ERR(page))
+ return PTR_ERR(page);
+ p = kmap_atomic(page, KM_USER0);
+ memcpy(buf + copied, p + offset, amt);
+ kunmap_atomic(p, KM_USER0);
+ mark_page_accessed(page);
+ page_cache_release(page);
+ copied += amt;
+ index++;
+ offset = 0;
+ } while(copied < size);
+ (*pos) += size;
+ return size;
}

/**
@@ -314,21 +367,19 @@ static int gfs2_readpages(struct file *file, struct address_space *mapping,
int ret = 0;
int do_unlock = 0;

- if (likely(file != &gfs2_internal_file_sentinel)) {
- if (file) {
- struct gfs2_file *gf = file->private_data;
- if (test_bit(GFF_EXLOCK, &gf->f_flags))
- goto skip_lock;
- }
- gfs2_holder_init(ip->i_gl, LM_ST_SHARED,
- LM_FLAG_TRY_1CB|GL_ATIME, &gh);
- do_unlock = 1;
- ret = gfs2_glock_nq_atime(&gh);
- if (ret == GLR_TRYFAILED)
- goto out_noerror;
- if (unlikely(ret))
- goto out_unlock;
+ if (file) {
+ struct gfs2_file *gf = file->private_data;
+ if (test_bit(GFF_EXLOCK, &gf->f_flags))
+ goto skip_lock;
}
+ gfs2_holder_init(ip->i_gl, LM_ST_SHARED,
+ LM_FLAG_TRY_1CB|GL_ATIME, &gh);
+ do_unlock = 1;
+ ret = gfs2_glock_nq_atime(&gh);
+ if (ret == GLR_TRYFAILED)
+ goto out_noerror;
+ if (unlikely(ret))
+ goto out_unlock;
skip_lock:
if (!gfs2_is_stuffed(ip))
ret = mpage_readpages(mapping, pages, nr_pages, gfs2_get_block);
diff --git a/fs/gfs2/ops_address.h b/fs/gfs2/ops_address.h
index fa1b5b3..e8fe83f 100644
--- a/fs/gfs2/ops_address.h
+++ b/fs/gfs2/ops_address.h
@@ -18,5 +18,8 @@ extern const struct address_space_operations gfs2_file_aops;
extern int gfs2_get_block(struct inode *inode, sector_t lblock,
struct buffer_head *bh_result, int create);
extern int gfs2_releasepage(struct page *page, gfp_t gfp_mask);
+extern int gfs2_internal_read(struct gfs2_inode *ip,
+ struct file_ra_state *ra_state,
+ char *buf, loff_t *pos, unsigned size);

#endif /* __OPS_ADDRESS_DOT_H__ */
diff --git a/fs/gfs2/ops_file.c b/fs/gfs2/ops_file.c
index bb11fd6..a729c86 100644
--- a/fs/gfs2/ops_file.c
+++ b/fs/gfs2/ops_file.c
@@ -33,7 +33,6 @@
#include "lm.h"
#include "log.h"
#include "meta_io.h"
-#include "ops_file.h"
#include "ops_vm.h"
#include "quota.h"
#include "rgrp.h"
@@ -41,50 +40,6 @@
#include "util.h"
#include "eaops.h"

-/*
- * Most fields left uninitialised to catch anybody who tries to
- * use them. f_flags set to prevent file_accessed() from touching
- * any other part of this. Its use is purely as a flag so that we
- * know (in readpage()) whether or not do to locking.
- */
-struct file gfs2_internal_file_sentinel = {
- .f_flags = O_NOATIME|O_RDONLY,
-};
-
-static int gfs2_read_actor(read_descriptor_t *desc, struct page *page,
- unsigned long offset, unsigned long size)
-{
- char *kaddr;
- unsigned long count = desc->count;
-
- if (size > count)
- size = count;
-
- kaddr = kmap(page);
- memcpy(desc->arg.data, kaddr + offset, size);
- kunmap(page);
-
- desc->count = count - size;
- desc->written += size;
- desc->arg.buf += size;
- return size;
-}
-
-int gfs2_internal_read(struct gfs2_inode *ip, struct file_ra_state *ra_state,
- char *buf, loff_t *pos, unsigned size)
-{
- struct inode *inode = &ip->i_inode;
- read_descriptor_t desc;
- desc.written = 0;
- desc.arg.data = buf;
- desc.count = size;
- desc.error = 0;
- do_generic_mapping_read(inode->i_mapping, ra_state,
- &gfs2_internal_file_sentinel, pos, &desc,
- gfs2_read_actor);
- return desc.written ? desc.written : desc.error;
-}
-
/**
* gfs2_llseek - seek to a location in a file
* @file: the file
diff --git a/fs/gfs2/ops_file.h b/fs/gfs2/ops_file.h
deleted file mode 100644
index 7e5d8ec..0000000
--- a/fs/gfs2/ops_file.h
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * Copyright (C) Sistina Software, Inc. 1997-2003 All rights reserved.
- * Copyright (C) 2004-2006 Red Hat, Inc. All rights reserved.
- *
- * This copyrighted material is made available to anyone wishing to use,
- * modify, copy, or redistribute it subject to the terms and conditions
- * of the GNU General Public License version 2.
- */
-
-#ifndef __OPS_FILE_DOT_H__
-#define __OPS_FILE_DOT_H__
-
-#include <linux/fs.h>
-struct gfs2_inode;
-
-extern struct file gfs2_internal_file_sentinel;
-extern int gfs2_internal_read(struct gfs2_inode *ip,
- struct file_ra_state *ra_state,
- char *buf, loff_t *pos, unsigned size);
-extern void gfs2_set_inode_flags(struct inode *inode);
-extern const struct file_operations gfs2_file_fops;
-extern const struct file_operations gfs2_dir_fops;
-
-#endif /* __OPS_FILE_DOT_H__ */
diff --git a/fs/gfs2/ops_inode.h b/fs/gfs2/ops_inode.h
index 34f0caa..edb519c 100644
--- a/fs/gfs2/ops_inode.h
+++ b/fs/gfs2/ops_inode.h
@@ -16,5 +16,9 @@ extern const struct inode_operations gfs2_file_iops;
extern const struct inode_operations gfs2_dir_iops;
extern const struct inode_operations gfs2_symlink_iops;
extern const struct inode_operations gfs2_dev_iops;
+extern const struct file_operations gfs2_file_fops;
+extern const struct file_operations gfs2_dir_fops;
+
+extern void gfs2_set_inode_flags(struct inode *inode);

#endif /* __OPS_INODE_DOT_H__ */
diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c
index addb51e..4996f0e 100644
--- a/fs/gfs2/quota.c
+++ b/fs/gfs2/quota.c
@@ -59,7 +59,6 @@
#include "super.h"
#include "trans.h"
#include "inode.h"
-#include "ops_file.h"
#include "ops_address.h"
#include "util.h"

@@ -793,11 +792,9 @@ static int do_glock(struct gfs2_quota_data *qd, int force_refresh,
struct gfs2_holder i_gh;
struct gfs2_quota_host q;
char buf[sizeof(struct gfs2_quota)];
- struct file_ra_state ra_state;
int error;
struct gfs2_quota_lvb *qlvb;

- file_ra_state_init(&ra_state, sdp->sd_quota_inode->i_mapping);
restart:
error = gfs2_glock_nq_init(qd->qd_gl, LM_ST_SHARED, 0, q_gh);
if (error)
@@ -820,8 +817,8 @@ restart:

memset(buf, 0, sizeof(struct gfs2_quota));
pos = qd2offset(qd);
- error = gfs2_internal_read(ip, &ra_state, buf,
- &pos, sizeof(struct gfs2_quota));
+ error = gfs2_internal_read(ip, NULL, buf, &pos,
+ sizeof(struct gfs2_quota));
if (error < 0)
goto fail_gunlock;

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 708c287..09848aa 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -25,10 +25,10 @@
#include "rgrp.h"
#include "super.h"
#include "trans.h"
-#include "ops_file.h"
#include "util.h"
#include "log.h"
#include "inode.h"
+#include "ops_address.h"

#define BFITNOENT ((u32)~0)
#define NO_BLOCK ((u64)~0)
--
1.5.1.2
 

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