From: Vyacheslav Dubeyko <slava@xxxxxxxxxxx>
Subject: [PATCH v2] nilfs2: fix issue with flush kernel thread after remount in RO mode because of driver's internal error or metadata corruption
DESCRIPTION:
NILFS2 driver remounts itself in RO mode in the case of metadata corruption discovering (for example, in the case of broken bmap discovering). But, usually, it takes place file system operations before remounting in RO mode. Thereby, NILFS2 driver can be in RO mode with presence of dirty pages in modified inodes' address spaces. It results in flush kernel thread's infinite trying to flush dirty pages in RO mode. As a result, it is possible to see such side effects as: (1) flush kernel thread occupies 50% - 99% of CPU time; (2) system can't be shutdowned without manual power switch off.
SYMPTOMS:
(1) System log contains error message: "Remounting filesystem read-only".
(2) The flush kernel thread occupies 50% - 99% of CPU time.
(3) The system can't be shutdowned without manual power switch off.
REPRODUCTION PATH:
(1) Create volume group with name "unencrypted" by means of vgcreate utility.
(2) Run script (prepared by Anthony Doggett <Anthony2486@xxxxxxxxxxxxxxxxx>):
----------------[BEGIN SCRIPT]--------------------
#!/bin/bash
VG=unencrypted
#apt-get install nilfs-tools darcs
lvcreate --size 2G --name ntest $VG
mkfs.nilfs2 -b 1024 -B 8192 /dev/mapper/$VG-ntest
mkdir /var/tmp/n
mkdir /var/tmp/n/ntest
mount /dev/mapper/$VG-ntest /var/tmp/n/ntest
mkdir /var/tmp/n/ntest/thedir
cd /var/tmp/n/ntest/thedir
sleep 2
date
darcs init
sleep 2
dmesg|tail -n 5
date
darcs whatsnew || true
date
sleep 2
dmesg|tail -n 5
----------------[END SCRIPT]--------------------
(3) Try to shutdown the system.
REPRODUCIBILITY: 100%
FIX:
The patch implements checking mount state of NILFS2 driver in nilfs_writepage(), nilfs_writepages() and nilfs_mdt_write_page() methods. If it is detected the RO mount state then all dirty pages are simply discarded with warning messages is written in system log.
Signed-off-by: Vyacheslav Dubeyko <slava@xxxxxxxxxxx>
CC: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxxxxxx>
Tested-by: Vyacheslav Dubeyko <slava@xxxxxxxxxxx>
---
fs/nilfs2/inode.c | 17 +++++++++++++
fs/nilfs2/mdt.c | 19 ++++++++++++---
fs/nilfs2/page.c | 70 +++++++++++++++++++++++++++++++++++++++--------------
fs/nilfs2/page.h | 3 ++-
4 files changed, 86 insertions(+), 23 deletions(-)
diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index 6b49f14..ba7a1da 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -175,6 +175,11 @@ static int nilfs_writepages(struct address_space *mapping,
struct inode *inode = mapping->host;
int err = 0;
+ if (inode->i_sb->s_flags & MS_RDONLY) {
+ nilfs_clear_dirty_pages(mapping, false);
+ return -EROFS;
+ }
+
if (wbc->sync_mode == WB_SYNC_ALL)
err = nilfs_construct_dsync_segment(inode->i_sb, inode,
wbc->range_start,
@@ -187,6 +192,18 @@ static int nilfs_writepage(struct page *page, struct writeback_control *wbc)
struct inode *inode = page->mapping->host;
int err;
+ if (inode && (inode->i_sb->s_flags & MS_RDONLY)) {
+ /*
+ * It means that filesystem was remounted in read-only
+ * mode because of error or metadata corruption. But we
+ * have dirty pages that try to be flushed in background.
+ * So, here we simply discard this dirty page.
+ */
+ nilfs_clear_dirty_page(page, false);
+ unlock_page(page);
+ return -EROFS;
+ }
+
redirty_page_for_writepage(wbc, page);
unlock_page(page);
diff --git a/fs/nilfs2/mdt.c b/fs/nilfs2/mdt.c
index f9897d0..c4dcd1d 100644
--- a/fs/nilfs2/mdt.c
+++ b/fs/nilfs2/mdt.c
@@ -375,14 +375,25 @@ int nilfs_mdt_fetch_dirty(struct inode *inode)
static int
nilfs_mdt_write_page(struct page *page, struct writeback_control *wbc)
{
- struct inode *inode;
+ struct inode *inode = page->mapping->host;
struct super_block *sb;
int err = 0;
+ if (inode && (inode->i_sb->s_flags & MS_RDONLY)) {
+ /*
+ * It means that filesystem was remounted in read-only
+ * mode because of error or metadata corruption. But we
+ * have dirty pages that try to be flushed in background.
+ * So, here we simply discard this dirty page.
+ */
+ nilfs_clear_dirty_page(page, false);
+ unlock_page(page);
+ return -EROFS;
+ }
+
redirty_page_for_writepage(wbc, page);
unlock_page(page);
- inode = page->mapping->host;
if (!inode)
return 0;
@@ -561,10 +572,10 @@ void nilfs_mdt_restore_from_shadow_map(struct inode *inode)
if (mi->mi_palloc_cache)
nilfs_palloc_clear_cache(inode);
- nilfs_clear_dirty_pages(inode->i_mapping);
+ nilfs_clear_dirty_pages(inode->i_mapping, true);
nilfs_copy_back_pages(inode->i_mapping, &shadow->frozen_data);
- nilfs_clear_dirty_pages(&ii->i_btnode_cache);
+ nilfs_clear_dirty_pages(&ii->i_btnode_cache, true);
nilfs_copy_back_pages(&ii->i_btnode_cache, &shadow->frozen_btnodes);
nilfs_bmap_restore(ii->i_bmap, &shadow->bmap_store);
diff --git a/fs/nilfs2/page.c b/fs/nilfs2/page.c
index 07f76db..2a2187f 100644
--- a/fs/nilfs2/page.c
+++ b/fs/nilfs2/page.c
@@ -370,7 +370,12 @@ repeat:
goto repeat;
}
-void nilfs_clear_dirty_pages(struct address_space *mapping)
+/**
+ * nilfs_clear_dirty_pages - discard dirty pages in address space
+ * @mapping: address space with dirty pages for discarding
+ * @silent: suppress [true] or print [false] warning messages
+ */
+void nilfs_clear_dirty_pages(struct address_space *mapping, bool silent)
{
struct pagevec pvec;
unsigned int i;
@@ -382,25 +387,9 @@ void nilfs_clear_dirty_pages(struct address_space *mapping)
PAGEVEC_SIZE)) {
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i];
- struct buffer_head *bh, *head;
lock_page(page);
- ClearPageUptodate(page);
- ClearPageMappedToDisk(page);
- bh = head = page_buffers(page);
- do {
- lock_buffer(bh);
- clear_buffer_dirty(bh);
- clear_buffer_nilfs_volatile(bh);
- clear_buffer_nilfs_checked(bh);
- clear_buffer_nilfs_redirected(bh);
- clear_buffer_uptodate(bh);
- clear_buffer_mapped(bh);
- unlock_buffer(bh);
- bh = bh->b_this_page;
- } while (bh != head);
-
- __nilfs_clear_page_dirty(page);
+ nilfs_clear_dirty_page(page, silent);
unlock_page(page);
}
pagevec_release(&pvec);
@@ -408,6 +397,51 @@ void nilfs_clear_dirty_pages(struct address_space *mapping)
}
}
+/**
+ * nilfs_clear_dirty_page - discard dirty page
+ * @page: dirty page that will be discarded
+ * @silent: suppress [true] or print [false] warning messages
+ */
+void nilfs_clear_dirty_page(struct page *page, bool silent)
+{
+ struct inode *inode = page->mapping->host;
+ struct super_block *sb = inode->i_sb;
+
+ BUG_ON(!test_bit(PG_locked, &page->flags));
+
+ if (!silent) {
+ nilfs_warning(sb, __func__,
+ "discard page: offset %lld, ino %lu",
+ page_offset(page), inode->i_ino);
+ }
+
+ ClearPageUptodate(page);
+ ClearPageMappedToDisk(page);
+
+ if (page_has_buffers(page)) {
+ struct buffer_head *bh, *head;
+
+ bh = head = page_buffers(page);
+ do {
+ lock_buffer(bh);
+ if (!silent) {
+ nilfs_warning(sb, __func__,
+ "discard block %llu, size %lu",
+ (u64)bh->b_blocknr, bh->b_size);
+ }
+ clear_buffer_dirty(bh);
+ clear_buffer_nilfs_volatile(bh);
+ clear_buffer_nilfs_checked(bh);
+ clear_buffer_nilfs_redirected(bh);
+ clear_buffer_uptodate(bh);
+ clear_buffer_mapped(bh);
+ unlock_buffer(bh);
+ } while (bh = bh->b_this_page, bh != head);
+ }
+
+ __nilfs_clear_page_dirty(page);
+}
+
unsigned nilfs_page_count_clean_buffers(struct page *page,
unsigned from, unsigned to)
{
diff --git a/fs/nilfs2/page.h b/fs/nilfs2/page.h
index fb7de71..ef30c5c 100644
--- a/fs/nilfs2/page.h
+++ b/fs/nilfs2/page.h
@@ -55,7 +55,8 @@ void nilfs_page_bug(struct page *);
int nilfs_copy_dirty_pages(struct address_space *, struct address_space *);
void nilfs_copy_back_pages(struct address_space *, struct address_space *);
-void nilfs_clear_dirty_pages(struct address_space *);
+void nilfs_clear_dirty_page(struct page *, bool);
+void nilfs_clear_dirty_pages(struct address_space *, bool);
void nilfs_mapping_init(struct address_space *mapping, struct inode *inode,
struct backing_dev_info *bdi);
unsigned nilfs_page_count_clean_buffers(struct page *, unsigned, unsigned);
--
1.7.9.5
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
