ext4: don't leave PageWriteback set after memory failure

In ext4_bio_write_page(), if the memory allocation for the struct
ext4_io_page fails, it returns with the page's PageWriteback flag set.
This will end up causing the page not to skip writeback in
WB_SYNC_NONE mode, and in WB_SYNC_ALL mode (i.e., on a sync, fsync, or
umount) the writeback daemon will get stuck forever on the
wait_on_page_writeback() function in write_cache_pages_da().

Or, if journalling is enabled and the file gets deleted, it the
journal thread can get stuck in journal_finish_inode_data_buffers()
call to filemap_fdatawait().

Another place where things can get hung up is in
truncate_inode_pages(), called out of ext4_evict_inode().

Fix this by not setting PageWriteback until after we have successfully
allocated the struct ext4_io_page.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index 68d92a8..d5c391f 100644 (file)
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -381,8 +381,6 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
 
        BUG_ON(!PageLocked(page));
        BUG_ON(PageWriteback(page));
-       set_page_writeback(page);
-       ClearPageError(page);
 
        io_page = kmem_cache_alloc(io_page_cachep, GFP_NOFS);
        if (!io_page) {
@@ -393,6 +391,8 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
        io_page->p_page = page;
        atomic_set(&io_page->p_count, 1);
        get_page(page);
+       set_page_writeback(page);
+       ClearPageError(page);
 
        for (bh = head = page_buffers(page), block_start = 0;
             bh != head || !block_start;