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Date: Mon, 8 Apr 2013 23:32:25 +0200
From: Jan Kara <jack@...e.cz>
To: Ted Tso <tytso@....edu>
Cc: linux-ext4@...r.kernel.org, Jan Kara <jack@...e.cz>
Subject: [PATCH 20/29] ext4: Use transaction reservation for extent conversion in ext4_end_io
Later we would like to clear PageWriteback bit only after extent conversion
from unwritten to written extents is performed. However it is not possible
to start a transaction after PageWriteback is set because that violates
lock ordering (and is easy to deadlock). So we have to reserve a transaction
before locking pages and sending them for IO and later we use the transaction
for extent conversion from ext4_end_io().
Signed-off-by: Jan Kara <jack@...e.cz>
---
fs/ext4/ext4.h | 12 +++++++++---
fs/ext4/ext4_jbd2.h | 3 ++-
fs/ext4/extents.c | 39 ++++++++++++++++++++++++++++-----------
fs/ext4/inode.c | 32 ++++++++++++++++++++++++++++++--
fs/ext4/page-io.c | 11 ++++++++---
5 files changed, 77 insertions(+), 20 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 3c3827a..65adf0d 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -182,10 +182,13 @@ struct ext4_map_blocks {
#define EXT4_IO_END_DIRECT 0x0004
/*
- * For converting uninitialized extents on a work queue.
+ * For converting uninitialized extents on a work queue. 'handle' is used for
+ * buffered writeback.
*/
typedef struct ext4_io_end {
struct list_head list; /* per-file finished IO list */
+ handle_t *handle; /* handle reserved for extent
+ * conversion */
struct inode *inode; /* file being written to */
unsigned int flag; /* unwritten or not */
loff_t offset; /* offset in the file */
@@ -1314,6 +1317,9 @@ static inline void ext4_set_io_unwritten_flag(struct inode *inode,
struct ext4_io_end *io_end)
{
if (!(io_end->flag & EXT4_IO_END_UNWRITTEN)) {
+ /* Writeback has to have coversion transaction reserved */
+ WARN_ON(!io_end->handle &&
+ !(io_end->flag & EXT4_IO_END_DIRECT));
io_end->flag |= EXT4_IO_END_UNWRITTEN;
atomic_inc(&EXT4_I(inode)->i_unwritten);
}
@@ -2550,8 +2556,8 @@ extern void ext4_ext_init(struct super_block *);
extern void ext4_ext_release(struct super_block *);
extern long ext4_fallocate(struct file *file, int mode, loff_t offset,
loff_t len);
-extern int ext4_convert_unwritten_extents(struct inode *inode, loff_t offset,
- ssize_t len);
+extern int ext4_convert_unwritten_extents(handle_t *handle, struct inode *inode,
+ loff_t offset, ssize_t len);
extern int ext4_map_blocks(handle_t *handle, struct inode *inode,
struct ext4_map_blocks *map, int flags);
extern int ext4_ext_calc_metadata_amount(struct inode *inode,
diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h
index bb17931..88e95d7 100644
--- a/fs/ext4/ext4_jbd2.h
+++ b/fs/ext4/ext4_jbd2.h
@@ -132,7 +132,8 @@ static inline int ext4_jbd2_credits_xattr(struct inode *inode)
#define EXT4_HT_MIGRATE 8
#define EXT4_HT_MOVE_EXTENTS 9
#define EXT4_HT_XATTR 10
-#define EXT4_HT_MAX 11
+#define EXT4_HT_EXT_CONVERT 11
+#define EXT4_HT_MAX 12
/**
* struct ext4_journal_cb_entry - Base structure for callback information.
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 8064b71..ae22735 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4484,10 +4484,9 @@ retry:
* function, to convert the fallocated extents after IO is completed.
* Returns 0 on success.
*/
-int ext4_convert_unwritten_extents(struct inode *inode, loff_t offset,
- ssize_t len)
+int ext4_convert_unwritten_extents(handle_t *handle, struct inode *inode,
+ loff_t offset, ssize_t len)
{
- handle_t *handle;
unsigned int max_blocks;
int ret = 0;
int ret2 = 0;
@@ -4502,16 +4501,31 @@ int ext4_convert_unwritten_extents(struct inode *inode, loff_t offset,
max_blocks = ((EXT4_BLOCK_ALIGN(len + offset, blkbits) >> blkbits) -
map.m_lblk);
/*
- * credits to insert 1 extent into extent tree
+ * This is somewhat ugly but the idea is clear: When transaction is
+ * reserved, everything goes into it. Otherwise we rather start several
+ * smaller transactions for conversion of each extent separately.
*/
- credits = ext4_chunk_trans_blocks(inode, max_blocks);
+ if (handle) {
+ handle = ext4_journal_start_reserved(handle);
+ if (IS_ERR(handle))
+ return PTR_ERR(handle);
+ credits = 0;
+ } else {
+ /*
+ * credits to insert 1 extent into extent tree
+ */
+ credits = ext4_chunk_trans_blocks(inode, max_blocks);
+ }
while (ret >= 0 && ret < max_blocks) {
map.m_lblk += ret;
map.m_len = (max_blocks -= ret);
- handle = ext4_journal_start(inode, EXT4_HT_MAP_BLOCKS, credits);
- if (IS_ERR(handle)) {
- ret = PTR_ERR(handle);
- break;
+ if (credits) {
+ handle = ext4_journal_start(inode, EXT4_HT_MAP_BLOCKS,
+ credits);
+ if (IS_ERR(handle)) {
+ ret = PTR_ERR(handle);
+ break;
+ }
}
ret = ext4_map_blocks(handle, inode, &map,
EXT4_GET_BLOCKS_IO_CONVERT_EXT);
@@ -4522,10 +4536,13 @@ int ext4_convert_unwritten_extents(struct inode *inode, loff_t offset,
inode->i_ino, map.m_lblk,
map.m_len, ret);
ext4_mark_inode_dirty(handle, inode);
- ret2 = ext4_journal_stop(handle);
- if (ret <= 0 || ret2 )
+ if (credits)
+ ret2 = ext4_journal_stop(handle);
+ if (ret <= 0 || ret2)
break;
}
+ if (!credits)
+ ret2 = ext4_journal_stop(handle);
return ret > 0 ? ret2 : ret;
}
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 0602a09..f8e78ce 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1327,6 +1327,8 @@ static void ext4_da_page_release_reservation(struct page *page,
struct mpage_da_data {
struct inode *inode;
struct writeback_control *wbc;
+ handle_t *reserved_handle; /* Handle reserved for conversion */
+
pgoff_t first_page; /* The first page to write */
pgoff_t next_page; /* Current page to examine */
pgoff_t last_page; /* Last page to examine */
@@ -1973,8 +1975,13 @@ static int mpage_map_one_extent(handle_t *handle, struct mpage_da_data *mpd)
err = ext4_map_blocks(handle, inode, map, get_blocks_flags);
if (err < 0)
return err;
- if (map->m_flags & EXT4_MAP_UNINIT)
+ if (map->m_flags & EXT4_MAP_UNINIT) {
+ if (!mpd->io_submit.io_end->handle) {
+ mpd->io_submit.io_end->handle = mpd->reserved_handle;
+ mpd->reserved_handle = NULL;
+ }
ext4_set_io_unwritten_flag(inode, mpd->io_submit.io_end);
+ }
BUG_ON(map->m_len == 0);
if (map->m_flags & EXT4_MAP_NEW) {
@@ -2274,6 +2281,7 @@ static int ext4_da_writepages(struct address_space *mapping,
mpd.inode = inode;
mpd.wbc = wbc;
+ mpd.reserved_handle = NULL;
ext4_io_submit_init(&mpd.io_submit, wbc);
retry:
if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
@@ -2288,6 +2296,23 @@ retry:
break;
}
+ /* Reserve handle if it may be needed for extent conversion */
+ if (ext4_should_dioread_nolock(inode) && !mpd.reserved_handle) {
+ /*
+ * We may need to convert upto one extent per block in
+ * the page and we may dirty the inode.
+ */
+ mpd.reserved_handle = ext4_journal_reserve(inode,
+ EXT4_HT_EXT_CONVERT,
+ 1 + (PAGE_CACHE_SIZE >> inode->i_blkbits));
+ if (IS_ERR(mpd.reserved_handle)) {
+ ret = PTR_ERR(mpd.reserved_handle);
+ mpd.reserved_handle = NULL;
+ ext4_put_io_end(mpd.io_submit.io_end);
+ break;
+ }
+ }
+
/*
* We have two constraints: We find one extent to map and we
* must always write out whole page (makes a difference when
@@ -2364,6 +2389,9 @@ retry:
*/
mapping->writeback_index = mpd.first_page;
+ if (mpd.reserved_handle)
+ ext4_journal_free_reserved(mpd.reserved_handle);
+
out_writepages:
trace_ext4_da_writepages_result(inode, wbc, ret,
nr_to_write - wbc->nr_to_write);
@@ -2977,7 +3005,7 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb,
* for non AIO case, since the IO is already
* completed, we could do the conversion right here
*/
- err = ext4_convert_unwritten_extents(inode,
+ err = ext4_convert_unwritten_extents(NULL, inode,
offset, ret);
if (err < 0)
ret = err;
diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index cc59cd9..e8ee4da 100644
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -55,6 +55,7 @@ static void ext4_release_io_end(ext4_io_end_t *io_end)
{
BUG_ON(!list_empty(&io_end->list));
BUG_ON(io_end->flag & EXT4_IO_END_UNWRITTEN);
+ WARN_ON(io_end->handle);
if (atomic_dec_and_test(&EXT4_I(io_end->inode)->i_ioend_count))
wake_up_all(ext4_ioend_wq(io_end->inode));
@@ -81,13 +82,15 @@ static int ext4_end_io(ext4_io_end_t *io)
struct inode *inode = io->inode;
loff_t offset = io->offset;
ssize_t size = io->size;
+ handle_t *handle = io->handle;
int ret = 0;
ext4_debug("ext4_end_io_nolock: io 0x%p from inode %lu,list->next 0x%p,"
"list->prev 0x%p\n",
io, inode->i_ino, io->list.next, io->list.prev);
- ret = ext4_convert_unwritten_extents(inode, offset, size);
+ io->handle = NULL; /* Following call will use up the handle */
+ ret = ext4_convert_unwritten_extents(handle, inode, offset, size);
if (ret < 0) {
ext4_msg(inode->i_sb, KERN_EMERG,
"failed to convert unwritten extents to written "
@@ -217,8 +220,10 @@ int ext4_put_io_end(ext4_io_end_t *io_end)
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);
+ err = ext4_convert_unwritten_extents(io_end->handle,
+ io_end->inode, io_end->offset,
+ io_end->size);
+ io_end->handle = NULL;
ext4_clear_io_unwritten_flag(io_end);
}
ext4_release_io_end(io_end);
--
1.7.1
--
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