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Date: Mon, 11 Jan 2021 17:42:53 +0800
From: Chao Yu <yuchao0@...wei.com>
To: <jaegeuk@...nel.org>
CC: <linux-f2fs-devel@...ts.sourceforge.net>,
<linux-kernel@...r.kernel.org>, <chao@...nel.org>,
Chao Yu <yuchao0@...wei.com>
Subject: [PATCH v2] f2fs: compress: fix potential deadlock
generic/269 reports a hangtask issue, the root cause is ABBA deadlock
described as below:
Thread A Thread B
- down_write(&sbi->gc_lock) -- A
- f2fs_write_data_pages
- lock all pages in cluster -- B
- f2fs_write_multi_pages
- f2fs_write_raw_pages
- f2fs_write_single_data_page
- f2fs_balance_fs
- down_write(&sbi->gc_lock) -- A
- f2fs_gc
- do_garbage_collect
- ra_data_block
- pagecache_get_page -- B
To fix this, it needs to avoid calling f2fs_balance_fs() if there is
still cluster pages been locked in context of cluster writeback, so
instead, let's call f2fs_balance_fs() in the end of
f2fs_write_raw_pages() when all cluster pages were unlocked.
Fixes: 4c8ff7095bef ("f2fs: support data compression")
Signed-off-by: Chao Yu <yuchao0@...wei.com>
---
v2:
- place f2fs_balance_fs() in f2fs_write_raw_pages() correctly.
fs/f2fs/compress.c | 5 ++++-
fs/f2fs/data.c | 10 ++++++----
fs/f2fs/f2fs.h | 2 +-
3 files changed, 11 insertions(+), 6 deletions(-)
diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index cb16b0437bd4..c4f0b2a3a79d 100644
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -1461,7 +1461,7 @@ static int f2fs_write_raw_pages(struct compress_ctx *cc,
ret = f2fs_write_single_data_page(cc->rpages[i], &_submitted,
NULL, NULL, wbc, io_type,
- compr_blocks);
+ compr_blocks, false);
if (ret) {
if (ret == AOP_WRITEPAGE_ACTIVATE) {
unlock_page(cc->rpages[i]);
@@ -1496,6 +1496,9 @@ static int f2fs_write_raw_pages(struct compress_ctx *cc,
*submitted += _submitted;
}
+
+ f2fs_balance_fs(F2FS_M_SB(mapping), true);
+
return 0;
out_err:
for (++i; i < cc->cluster_size; i++) {
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 427a527eb17e..f8578fad7cd1 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2684,7 +2684,8 @@ int f2fs_write_single_data_page(struct page *page, int *submitted,
sector_t *last_block,
struct writeback_control *wbc,
enum iostat_type io_type,
- int compr_blocks)
+ int compr_blocks,
+ bool allow_balance)
{
struct inode *inode = page->mapping->host;
struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
@@ -2822,7 +2823,7 @@ int f2fs_write_single_data_page(struct page *page, int *submitted,
}
unlock_page(page);
if (!S_ISDIR(inode->i_mode) && !IS_NOQUOTA(inode) &&
- !F2FS_I(inode)->cp_task)
+ !F2FS_I(inode)->cp_task && allow_balance)
f2fs_balance_fs(sbi, need_balance_fs);
if (unlikely(f2fs_cp_error(sbi))) {
@@ -2869,7 +2870,7 @@ static int f2fs_write_data_page(struct page *page,
#endif
return f2fs_write_single_data_page(page, NULL, NULL, NULL,
- wbc, FS_DATA_IO, 0);
+ wbc, FS_DATA_IO, 0, true);
}
/*
@@ -3037,7 +3038,8 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
}
#endif
ret = f2fs_write_single_data_page(page, &submitted,
- &bio, &last_block, wbc, io_type, 0);
+ &bio, &last_block, wbc, io_type,
+ 0, true);
if (ret == AOP_WRITEPAGE_ACTIVATE)
unlock_page(page);
#ifdef CONFIG_F2FS_FS_COMPRESSION
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 67086c6072ad..5cc1486f0b9f 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -3511,7 +3511,7 @@ int f2fs_write_single_data_page(struct page *page, int *submitted,
struct bio **bio, sector_t *last_block,
struct writeback_control *wbc,
enum iostat_type io_type,
- int compr_blocks);
+ int compr_blocks, bool allow_balance);
void f2fs_invalidate_page(struct page *page, unsigned int offset,
unsigned int length);
int f2fs_release_page(struct page *page, gfp_t wait);
--
2.29.2
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