Re: [PATCH] 2.6.11-mm1 "nobh" support for ext3 writeback mode
From: Badari Pulavarty
Date: Fri Mar 04 2005 - 20:07:11 EST
On Fri, 2005-03-04 at 16:31, Andrew Morton wrote:
> Andrew Morton <akpm@xxxxxxxx> wrote:
> >
> > page reclaim can come in, grab the page lock and
> > whip the page off the mapping.
>
> No it can't - we hold an additional ref on the page, so reclaim will back
> off. Still, it feels a bit flakey.
>
> And we're not supposed to take lock_page() inside journal_start, because
> that's a ranking violation. Probably i_sem will prevent an actual deadlock
> occurring, however.
>
Here is the new patch to deal with locking, with more code :(
Thanks,
Badari
diff -Naurp -Xdontdiff linux-2.6.11/fs/ext3/inode.c linux-2.6.11.new/fs/ext3/inode.c
--- linux-2.6.11/fs/ext3/inode.c 2005-03-04 16:43:22.536143072 -0800
+++ linux-2.6.11.new/fs/ext3/inode.c 2005-03-04 17:43:16.719744112 -0800
@@ -20,6 +20,7 @@
* (jj@xxxxxxxxxxxxxxxxxxxxxx)
*
* Assorted race fixes, rewrite of ext3_get_block() by Al Viro, 2000
+ * Add "nobh" support for ext3 writeback mode - pbadari@xxxxxxxxxx
*/
#include <linux/module.h>
@@ -1016,7 +1017,10 @@ retry:
ret = PTR_ERR(handle);
goto out;
}
- ret = block_prepare_write(page, from, to, ext3_get_block);
+ if (test_opt(inode->i_sb, NOBH))
+ ret = nobh_prepare_write(page, from, to, ext3_get_block);
+ else
+ ret = block_prepare_write(page, from, to, ext3_get_block);
if (ret)
goto prepare_write_failed;
@@ -1100,7 +1104,12 @@ static int ext3_writeback_commit_write(s
new_i_size = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
if (new_i_size > EXT3_I(inode)->i_disksize)
EXT3_I(inode)->i_disksize = new_i_size;
- ret = generic_commit_write(file, page, from, to);
+
+ if (test_opt(inode->i_sb, NOBH))
+ ret = nobh_commit_write(file, page, from, to);
+ else
+ ret = generic_commit_write(file, page, from, to);
+
ret2 = ext3_journal_stop(handle);
if (!ret)
ret = ret2;
@@ -1385,7 +1394,11 @@ static int ext3_writeback_writepage(stru
goto out_fail;
}
- ret = block_write_full_page(page, ext3_get_block, wbc);
+ if (test_opt(inode->i_sb, NOBH))
+ ret = nobh_writepage(page, ext3_get_block, wbc);
+ else
+ ret = block_write_full_page(page, ext3_get_block, wbc);
+
err = ext3_journal_stop(handle);
if (!ret)
ret = err;
@@ -1646,13 +1659,46 @@ static int ext3_block_truncate_page(hand
unsigned blocksize, iblock, length, pos;
struct inode *inode = mapping->host;
struct buffer_head *bh;
- int err;
+ int err = 0;
void *kaddr;
blocksize = inode->i_sb->s_blocksize;
length = blocksize - (offset & (blocksize - 1));
iblock = index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);
+ if (test_opt(inode->i_sb, NOBH) && !page_has_buffers(page)) {
+ if (!PageUptodate(page)) {
+ struct buffer_head map_bh;
+ bh = &map_bh;
+ bh->b_state = 0;
+ clear_buffer_mapped(bh);
+ ext3_get_block(inode, iblock, bh, 0);
+ if (!buffer_mapped(bh))
+ goto unlock;
+ err = -EIO;
+ set_bh_page(bh, page, 0);
+ bh->b_this_page = 0;
+ bh->b_size = 1 << inode->i_blkbits;
+ ll_rw_block(READ, 1, &bh);
+ wait_on_buffer(bh);
+ if (!buffer_uptodate(bh))
+ goto unlock;
+ SetPageMappedToDisk(page);
+ }
+ if (err == 0 && PageUptodate(page)) {
+ kaddr = kmap_atomic(page, KM_USER0);
+ memset(kaddr + offset, 0, length);
+ flush_dcache_page(page);
+ kunmap_atomic(kaddr, KM_USER0);
+ set_page_dirty(page);
+ goto unlock;
+ }
+ /*
+ * Well, we tried to work without buffers and failed.
+ * Fallback to creating buffers
+ */
+ }
+
if (!page_has_buffers(page))
create_empty_buffers(page, blocksize, 0);
diff -Naurp -Xdontdiff linux-2.6.11/fs/ext3/super.c linux-2.6.11.new/fs/ext3/super.c
--- linux-2.6.11/fs/ext3/super.c 2005-03-01 23:38:38.000000000 -0800
+++ linux-2.6.11.new/fs/ext3/super.c 2005-03-04 16:45:22.038975880 -0800
@@ -576,7 +576,7 @@ enum {
Opt_resgid, Opt_resuid, Opt_sb, Opt_err_cont, Opt_err_panic, Opt_err_ro,
Opt_nouid32, Opt_check, Opt_nocheck, Opt_debug, Opt_oldalloc, Opt_orlov,
Opt_user_xattr, Opt_nouser_xattr, Opt_acl, Opt_noacl,
- Opt_reservation, Opt_noreservation, Opt_noload,
+ Opt_reservation, Opt_noreservation, Opt_noload, Opt_nobh,
Opt_commit, Opt_journal_update, Opt_journal_inum,
Opt_abort, Opt_data_journal, Opt_data_ordered, Opt_data_writeback,
Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
@@ -611,6 +611,7 @@ static match_table_t tokens = {
{Opt_reservation, "reservation"},
{Opt_noreservation, "noreservation"},
{Opt_noload, "noload"},
+ {Opt_nobh, "nobh"},
{Opt_commit, "commit=%u"},
{Opt_journal_update, "journal=update"},
{Opt_journal_inum, "journal=%u"},
@@ -924,6 +925,9 @@ clear_qf_name:
match_int(&args[0], &option);
*n_blocks_count = option;
break;
+ case Opt_nobh:
+ set_opt(sbi->s_mount_opt, NOBH);
+ break;
default:
printk (KERN_ERR
"EXT3-fs: Unrecognized mount option \"%s\" "
@@ -1563,6 +1567,19 @@ static int ext3_fill_super (struct super
break;
}
+ if (test_opt(sb, NOBH)) {
+ if (sb->s_blocksize_bits != PAGE_CACHE_SHIFT) {
+ printk(KERN_WARNING "EXT3-fs: Ignoring nobh option "
+ "since filesystem blocksize doesn't match "
+ "pagesize\n");
+ clear_opt(sbi->s_mount_opt, NOBH);
+ }
+ if (!(test_opt(sb, DATA_FLAGS) == EXT3_MOUNT_WRITEBACK_DATA)) {
+ printk(KERN_WARNING "EXT3-fs: Ignoring nobh option - "
+ "its supported only with writeback mode\n");
+ clear_opt(sbi->s_mount_opt, NOBH);
+ }
+ }
/*
* The journal_load will have done any necessary log recovery,
* so we can safely mount the rest of the filesystem now.
diff -Naurp -Xdontdiff linux-2.6.11/include/linux/ext3_fs.h linux-2.6.11.new/include/linux/ext3_fs.h
--- linux-2.6.11/include/linux/ext3_fs.h 2005-03-01 23:38:10.000000000 -0800
+++ linux-2.6.11.new/include/linux/ext3_fs.h 2005-03-04 16:46:29.101780784 -0800
@@ -357,6 +357,7 @@ struct ext3_inode {
#define EXT3_MOUNT_POSIX_ACL 0x08000 /* POSIX Access Control Lists */
#define EXT3_MOUNT_RESERVATION 0x10000 /* Preallocation */
#define EXT3_MOUNT_BARRIER 0x20000 /* Use block barriers */
+#define EXT3_MOUNT_NOBH 0x40000 /* No bufferheads */
/* Compatibility, for having both ext2_fs.h and ext3_fs.h included at once */
#ifndef _LINUX_EXT2_FS_H