ext4: use io_end for multiple bios
Change writeback path to create just one io_end structure for the
extent to which we submit IO and share it among bios writing that
extent. This prevents needless splitting and joining of unwritten
extents when they cannot be submitted as a single bio.
Bugs in ENOMEM handling found by Linux File System Verification project
(linuxtesting.org) and fixed by Alexey Khoroshilov
<khoroshilov@ispras.ru>.
CC: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index 4acf1f7..19599bd 100644
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -62,15 +62,28 @@
cancel_work_sync(&EXT4_I(inode)->i_unwritten_work);
}
-void ext4_free_io_end(ext4_io_end_t *io)
+static void ext4_release_io_end(ext4_io_end_t *io_end)
{
- BUG_ON(!io);
- BUG_ON(!list_empty(&io->list));
- BUG_ON(io->flag & EXT4_IO_END_UNWRITTEN);
+ BUG_ON(!list_empty(&io_end->list));
+ BUG_ON(io_end->flag & EXT4_IO_END_UNWRITTEN);
- if (atomic_dec_and_test(&EXT4_I(io->inode)->i_ioend_count))
- wake_up_all(ext4_ioend_wq(io->inode));
- kmem_cache_free(io_end_cachep, io);
+ if (atomic_dec_and_test(&EXT4_I(io_end->inode)->i_ioend_count))
+ wake_up_all(ext4_ioend_wq(io_end->inode));
+ if (io_end->flag & EXT4_IO_END_DIRECT)
+ inode_dio_done(io_end->inode);
+ if (io_end->iocb)
+ aio_complete(io_end->iocb, io_end->result, 0);
+ kmem_cache_free(io_end_cachep, io_end);
+}
+
+static void ext4_clear_io_unwritten_flag(ext4_io_end_t *io_end)
+{
+ struct inode *inode = io_end->inode;
+
+ io_end->flag &= ~EXT4_IO_END_UNWRITTEN;
+ /* Wake up anyone waiting on unwritten extent conversion */
+ if (atomic_dec_and_test(&EXT4_I(inode)->i_unwritten))
+ wake_up_all(ext4_ioend_wq(inode));
}
/* check a range of space and convert unwritten extents to written. */
@@ -93,13 +106,8 @@
"(inode %lu, offset %llu, size %zd, error %d)",
inode->i_ino, offset, size, ret);
}
- /* Wake up anyone waiting on unwritten extent conversion */
- if (atomic_dec_and_test(&EXT4_I(inode)->i_unwritten))
- wake_up_all(ext4_ioend_wq(inode));
- if (io->flag & EXT4_IO_END_DIRECT)
- inode_dio_done(inode);
- if (io->iocb)
- aio_complete(io->iocb, io->result, 0);
+ ext4_clear_io_unwritten_flag(io);
+ ext4_release_io_end(io);
return ret;
}
@@ -130,7 +138,7 @@
}
/* Add the io_end to per-inode completed end_io list. */
-void ext4_add_complete_io(ext4_io_end_t *io_end)
+static void ext4_add_complete_io(ext4_io_end_t *io_end)
{
struct ext4_inode_info *ei = EXT4_I(io_end->inode);
struct workqueue_struct *wq;
@@ -167,8 +175,6 @@
err = ext4_end_io(io);
if (unlikely(!ret && err))
ret = err;
- io->flag &= ~EXT4_IO_END_UNWRITTEN;
- ext4_free_io_end(io);
}
return ret;
}
@@ -200,10 +206,43 @@
atomic_inc(&EXT4_I(inode)->i_ioend_count);
io->inode = inode;
INIT_LIST_HEAD(&io->list);
+ atomic_set(&io->count, 1);
}
return io;
}
+void ext4_put_io_end_defer(ext4_io_end_t *io_end)
+{
+ if (atomic_dec_and_test(&io_end->count)) {
+ if (!(io_end->flag & EXT4_IO_END_UNWRITTEN) || !io_end->size) {
+ ext4_release_io_end(io_end);
+ return;
+ }
+ ext4_add_complete_io(io_end);
+ }
+}
+
+int ext4_put_io_end(ext4_io_end_t *io_end)
+{
+ int err = 0;
+
+ if (atomic_dec_and_test(&io_end->count)) {
+ if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
+ err = ext4_convert_unwritten_extents(io_end->inode,
+ io_end->offset, io_end->size);
+ ext4_clear_io_unwritten_flag(io_end);
+ }
+ ext4_release_io_end(io_end);
+ }
+ return err;
+}
+
+ext4_io_end_t *ext4_get_io_end(ext4_io_end_t *io_end)
+{
+ atomic_inc(&io_end->count);
+ return io_end;
+}
+
/*
* Print an buffer I/O error compatible with the fs/buffer.c. This
* provides compatibility with dmesg scrapers that look for a specific
@@ -286,12 +325,7 @@
bi_sector >> (inode->i_blkbits - 9));
}
- if (!(io_end->flag & EXT4_IO_END_UNWRITTEN)) {
- ext4_free_io_end(io_end);
- return;
- }
-
- ext4_add_complete_io(io_end);
+ ext4_put_io_end_defer(io_end);
}
void ext4_io_submit(struct ext4_io_submit *io)
@@ -305,40 +339,37 @@
bio_put(io->io_bio);
}
io->io_bio = NULL;
- io->io_op = 0;
+}
+
+void ext4_io_submit_init(struct ext4_io_submit *io,
+ struct writeback_control *wbc)
+{
+ io->io_op = (wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : WRITE);
+ io->io_bio = NULL;
io->io_end = NULL;
}
-static int io_submit_init(struct ext4_io_submit *io,
- struct inode *inode,
- struct writeback_control *wbc,
- struct buffer_head *bh)
+static int io_submit_init_bio(struct ext4_io_submit *io,
+ struct buffer_head *bh)
{
- ext4_io_end_t *io_end;
- struct page *page = bh->b_page;
int nvecs = bio_get_nr_vecs(bh->b_bdev);
struct bio *bio;
- io_end = ext4_init_io_end(inode, GFP_NOFS);
- if (!io_end)
- return -ENOMEM;
bio = bio_alloc(GFP_NOIO, min(nvecs, BIO_MAX_PAGES));
bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
bio->bi_bdev = bh->b_bdev;
- bio->bi_private = io->io_end = io_end;
bio->bi_end_io = ext4_end_bio;
-
- io_end->offset = (page->index << PAGE_CACHE_SHIFT) + bh_offset(bh);
-
+ bio->bi_private = ext4_get_io_end(io->io_end);
+ if (!io->io_end->size)
+ io->io_end->offset = (bh->b_page->index << PAGE_CACHE_SHIFT)
+ + bh_offset(bh);
io->io_bio = bio;
- io->io_op = (wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : WRITE);
io->io_next_block = bh->b_blocknr;
return 0;
}
static int io_submit_add_bh(struct ext4_io_submit *io,
struct inode *inode,
- struct writeback_control *wbc,
struct buffer_head *bh)
{
ext4_io_end_t *io_end;
@@ -349,18 +380,18 @@
ext4_io_submit(io);
}
if (io->io_bio == NULL) {
- ret = io_submit_init(io, inode, wbc, bh);
+ ret = io_submit_init_bio(io, bh);
if (ret)
return ret;
}
- io_end = io->io_end;
- if (test_clear_buffer_uninit(bh))
- ext4_set_io_unwritten_flag(inode, io_end);
- io->io_end->size += bh->b_size;
- io->io_next_block++;
ret = bio_add_page(io->io_bio, bh->b_page, bh->b_size, bh_offset(bh));
if (ret != bh->b_size)
goto submit_and_retry;
+ io_end = io->io_end;
+ if (test_clear_buffer_uninit(bh))
+ ext4_set_io_unwritten_flag(inode, io_end);
+ io_end->size += bh->b_size;
+ io->io_next_block++;
return 0;
}
@@ -432,7 +463,7 @@
do {
if (!buffer_async_write(bh))
continue;
- ret = io_submit_add_bh(io, inode, wbc, bh);
+ ret = io_submit_add_bh(io, inode, bh);
if (ret) {
/*
* We only get here on ENOMEM. Not much else