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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" <tytso@mit.edu>
This commit is contained in:
Theodore Ts'o 2010-11-08 13:45:33 -05:00
parent f7ad6d2e92
commit 83668e7141
2 changed files with 16 additions and 24 deletions
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2
fs/ext4/ext4.h
View File

@ -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

38
fs/ext4/page-io.c
View File

@ -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 @@ static int io_submit_add_bh(struct ext4_io_submit *io,
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;
}