A deadlock can be occurred:
Thread 1] Thread 2]
- f2fs_write_data_pages - f2fs_write_begin
- lock_page(page #0)
- grab_cache_page(page #X)
- get_node_page(inode_page)
- grab_cache_page(page #0)
: to convert inline_data
- f2fs_write_data_page
- f2fs_write_inline_data
- get_node_page(inode_page)
In this case, trying to lock inode_page and page #0 causes deadlock.
In order to avoid this, this patch adds a rule for this locking policy,
which is that page #0 should be locked followed by inode_page lock.
Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
---
fs/f2fs/data.c | 28 ++++++++++++++--------------
1 file changed, 14 insertions(+), 14 deletions(-)
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 12dd58a..c7bc626 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -936,6 +936,17 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping,
trace_f2fs_write_begin(inode, pos, len, flags);
f2fs_balance_fs(sbi);
+
+ /*
+ * We should check this at this moment to avoid deadlock on inode page
+ * and #0 page. The locking rule for inline_data conversion should be:
+ * lock_page(page #0) -> lock_page(inode_page)
+ */
+ if (index != 0) {
+ err = f2fs_convert_inline_inode(inode);
+ if (err)
+ goto fail;
+ }
repeat:
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page) {
@@ -960,21 +971,10 @@ repeat:
set_inode_flag(F2FS_I(inode), FI_DATA_EXIST);
sync_inode_page(&dn);
goto put_next;
- } else if (page->index == 0) {
- err = f2fs_convert_inline_page(&dn, page);
- if (err)
- goto put_fail;
- } else {
- struct page *p = grab_cache_page(inode->i_mapping, 0);
- if (!p) {
- err = -ENOMEM;
- goto put_fail;
- }
- err = f2fs_convert_inline_page(&dn, p);
- f2fs_put_page(p, 1);
- if (err)
- goto put_fail;
}
+ err = f2fs_convert_inline_page(&dn, page);
+ if (err)
+ goto put_fail;
}
err = f2fs_reserve_block(&dn, index);
if (err)
--
2.1.1
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