From 83668e7141c7a0aa4035bde94344b81f9cf966ab Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Mon, 8 Nov 2010 13:45:33 -0500 Subject: ext4: fix potential race when freeing ext4_io_page structures Use an atomic_t and make sure we don't free the structure while we might still be submitting I/O for that page. Signed-off-by: "Theodore Ts'o" --- fs/ext4/ext4.h | 2 +- fs/ext4/page-io.c | 38 +++++++++++++++----------------------- 2 files changed, 16 insertions(+), 24 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 670d134..6a5edea 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -177,7 +177,7 @@ struct mpage_da_data { struct ext4_io_page { struct page *p_page; - int p_count; + atomic_t p_count; }; #define MAX_IO_PAGES 128 diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c index a24c8cc..7f5451c 100644 --- a/fs/ext4/page-io.c +++ b/fs/ext4/page-io.c @@ -67,6 +67,15 @@ void ext4_ioend_wait(struct inode *inode) wait_event(*wq, (atomic_read(&EXT4_I(inode)->i_ioend_count) == 0)); } +static void put_io_page(struct ext4_io_page *io_page) +{ + if (atomic_dec_and_test(&io_page->p_count)) { + end_page_writeback(io_page->p_page); + put_page(io_page->p_page); + kmem_cache_free(io_page_cachep, io_page); + } +} + void ext4_free_io_end(ext4_io_end_t *io) { int i; @@ -75,15 +84,8 @@ void ext4_free_io_end(ext4_io_end_t *io) BUG_ON(!io); if (io->page) put_page(io->page); - for (i = 0; i < io->num_io_pages; i++) { - if (--io->pages[i]->p_count == 0) { - struct page *page = io->pages[i]->p_page; - - end_page_writeback(page); - put_page(page); - kmem_cache_free(io_page_cachep, io->pages[i]); - } - } + for (i = 0; i < io->num_io_pages; i++) + put_io_page(io->pages[i]); io->num_io_pages = 0; wq = to_ioend_wq(io->inode); if (atomic_dec_and_test(&EXT4_I(io->inode)->i_ioend_count) && @@ -235,13 +237,7 @@ static void ext4_end_bio(struct bio *bio, int error) } while (bh != head); } - if (--io_end->pages[i]->p_count == 0) { - struct page *page = io_end->pages[i]->p_page; - - end_page_writeback(page); - put_page(page); - kmem_cache_free(io_page_cachep, io_end->pages[i]); - } + put_io_page(io_end->pages[i]); /* * If this is a partial write which happened to make @@ -369,7 +365,7 @@ submit_and_retry: if ((io_end->num_io_pages == 0) || (io_end->pages[io_end->num_io_pages-1] != io_page)) { io_end->pages[io_end->num_io_pages++] = io_page; - io_page->p_count++; + atomic_inc(&io_page->p_count); } return 0; } @@ -398,7 +394,7 @@ int ext4_bio_write_page(struct ext4_io_submit *io, return -ENOMEM; } io_page->p_page = page; - io_page->p_count = 0; + atomic_set(&io_page->p_count, 1); get_page(page); for (bh = head = page_buffers(page), block_start = 0; @@ -430,10 +426,6 @@ int ext4_bio_write_page(struct ext4_io_submit *io, * PageWriteback bit from the page to prevent the system from * wedging later on. */ - if (io_page->p_count == 0) { - put_page(page); - end_page_writeback(page); - kmem_cache_free(io_page_cachep, io_page); - } + put_io_page(io_page); return ret; } -- cgit v1.1