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ext4: Invert lock ordering of page_lock and transaction start in dela…
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…lloc

With the reverse locking, we need to start a transation before taking
the page lock, so in ext4_da_writepages() we need to break the write-out
into chunks, and restart the journal for each chunck to ensure the
write-out fits in a single transaction.

Updated patch from Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
which fixes delalloc sync hang with journal lock inversion, and address
the performance regression issue.

Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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Mingming Cao authored and Theodore Ts'o committed Jul 11, 2008
1 parent 06d6cf6 commit 61628a3
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Showing 2 changed files with 152 additions and 59 deletions.
10 changes: 8 additions & 2 deletions fs/ext4/extents.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2565,6 +2565,7 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
int err = 0, depth, ret;
unsigned long allocated = 0;
struct ext4_allocation_request ar;
loff_t disksize;

__clear_bit(BH_New, &bh_result->b_state);
ext_debug("blocks %u/%lu requested for inode %u\n",
Expand Down Expand Up @@ -2755,8 +2756,13 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
newblock = ext_pblock(&newex);
allocated = ext4_ext_get_actual_len(&newex);
outnew:
if (extend_disksize && inode->i_size > EXT4_I(inode)->i_disksize)
EXT4_I(inode)->i_disksize = inode->i_size;
if (extend_disksize) {
disksize = ((loff_t) iblock + ar.len) << inode->i_blkbits;
if (disksize > i_size_read(inode))
disksize = i_size_read(inode);
if (disksize > EXT4_I(inode)->i_disksize)
EXT4_I(inode)->i_disksize = disksize;
}

set_buffer_new(bh_result);

Expand Down
201 changes: 144 additions & 57 deletions fs/ext4/inode.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -847,6 +847,7 @@ int ext4_get_blocks_handle(handle_t *handle, struct inode *inode,
struct ext4_inode_info *ei = EXT4_I(inode);
int count = 0;
ext4_fsblk_t first_block = 0;
loff_t disksize;


J_ASSERT(!(EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL));
Expand Down Expand Up @@ -922,8 +923,13 @@ int ext4_get_blocks_handle(handle_t *handle, struct inode *inode,
* protect it if you're about to implement concurrent
* ext4_get_block() -bzzz
*/
if (!err && extend_disksize && inode->i_size > ei->i_disksize)
ei->i_disksize = inode->i_size;
if (!err && extend_disksize) {
disksize = ((loff_t) iblock + count) << inode->i_blkbits;
if (disksize > i_size_read(inode))
disksize = i_size_read(inode);
if (disksize > ei->i_disksize)
ei->i_disksize = disksize;
}
if (err)
goto cleanup;

Expand Down Expand Up @@ -1683,13 +1689,11 @@ static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd, sector_t logical,
do {
if (cur_logical >= logical + blocks)
break;

if (buffer_delay(bh)) {
bh->b_blocknr = pblock;
clear_buffer_delay(bh);
} else if (buffer_mapped(bh)) {
} else if (buffer_mapped(bh))
BUG_ON(bh->b_blocknr != pblock);
}

cur_logical++;
pblock++;
Expand Down Expand Up @@ -1764,10 +1768,10 @@ static void mpage_da_map_blocks(struct mpage_da_data *mpd)
if (buffer_delay(lbh))
mpage_put_bnr_to_bhs(mpd, next, &new);

/* go for the remaining blocks */
next += new.b_size >> mpd->inode->i_blkbits;
remain -= new.b_size;
}
/* go for the remaining blocks */
next += new.b_size >> mpd->inode->i_blkbits;
remain -= new.b_size;
}
}

#define BH_FLAGS ((1 << BH_Uptodate) | (1 << BH_Mapped) | (1 << BH_Delay))
Expand Down Expand Up @@ -1993,18 +1997,14 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
static int ext4_da_get_block_write(struct inode *inode, sector_t iblock,
struct buffer_head *bh_result, int create)
{
int ret, needed_blocks = ext4_writepage_trans_blocks(inode);
int ret;
unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
loff_t disksize = EXT4_I(inode)->i_disksize;
handle_t *handle = NULL;

if (create) {
handle = ext4_journal_start(inode, needed_blocks);
if (IS_ERR(handle)) {
ret = PTR_ERR(handle);
goto out;
}
}
handle = ext4_journal_current_handle();
BUG_ON(handle == NULL);
BUG_ON(create == 0);

ret = ext4_get_blocks_wrap(handle, inode, iblock, max_blocks,
bh_result, create, 0, EXT4_DELALLOC_RSVED);
Expand All @@ -2029,65 +2029,157 @@ static int ext4_da_get_block_write(struct inode *inode, sector_t iblock,
up_write(&EXT4_I(inode)->i_data_sem);

if (EXT4_I(inode)->i_disksize == disksize) {
if (handle == NULL)
handle = ext4_journal_start(inode, 1);
if (!IS_ERR(handle))
ext4_mark_inode_dirty(handle, inode);
ret = ext4_mark_inode_dirty(handle, inode);
return ret;
}
}

ret = 0;
}

out:
if (handle && !IS_ERR(handle))
ext4_journal_stop(handle);

return ret;
}

static int ext4_bh_unmapped_or_delay(handle_t *handle, struct buffer_head *bh)
{
return !buffer_mapped(bh) || buffer_delay(bh);
}

/* FIXME!! only support data=writeback mode */
/*
* get called vi ext4_da_writepages after taking page lock
* We may end up doing block allocation here in case
* mpage_da_map_blocks failed to allocate blocks.
*/
static int ext4_da_writepage(struct page *page,
struct writeback_control *wbc)
{
struct inode *inode = page->mapping->host;
handle_t *handle = NULL;
int ret = 0;
int err;
loff_t size;
unsigned long len;
handle_t *handle = NULL;
struct buffer_head *page_bufs;
struct inode *inode = page->mapping->host;

if (ext4_journal_current_handle())
goto out_fail;
handle = ext4_journal_current_handle();
if (!handle) {
/*
* This can happen when we aren't called via
* ext4_da_writepages() but directly (shrink_page_list).
* We cannot easily start a transaction here so we just skip
* writing the page in case we would have to do so.
*/
size = i_size_read(inode);

handle = ext4_journal_start(inode, ext4_writepage_trans_blocks(inode));
if (IS_ERR(handle)) {
ret = PTR_ERR(handle);
goto out_fail;
page_bufs = page_buffers(page);
if (page->index == size >> PAGE_CACHE_SHIFT)
len = size & ~PAGE_CACHE_MASK;
else
len = PAGE_CACHE_SIZE;

if (walk_page_buffers(NULL, page_bufs, 0,
len, NULL, ext4_bh_unmapped_or_delay)) {
/*
* We can't do block allocation under
* page lock without a handle . So redirty
* the page and return
*/
BUG_ON(wbc->sync_mode != WB_SYNC_NONE);
redirty_page_for_writepage(wbc, page);
unlock_page(page);
return 0;
}
}

if (test_opt(inode->i_sb, NOBH) && ext4_should_writeback_data(inode))
ret = nobh_writepage(page, ext4_get_block, wbc);
ret = nobh_writepage(page, ext4_da_get_block_write, wbc);
else
ret = block_write_full_page(page, ext4_get_block, wbc);

if (!ret && inode->i_size > EXT4_I(inode)->i_disksize) {
EXT4_I(inode)->i_disksize = inode->i_size;
ext4_mark_inode_dirty(handle, inode);
}
ret = block_write_full_page(page, ext4_da_get_block_write, wbc);

err = ext4_journal_stop(handle);
if (!ret)
ret = err;
return ret;

out_fail:
redirty_page_for_writepage(wbc, page);
unlock_page(page);
return ret;
}


/*
* For now just follow the DIO way to estimate the max credits
* needed to write out EXT4_MAX_WRITEBACK_PAGES.
* todo: need to calculate the max credits need for
* extent based files, currently the DIO credits is based on
* indirect-blocks mapping way.
*
* Probably should have a generic way to calculate credits
* for DIO, writepages, and truncate
*/
#define EXT4_MAX_WRITEBACK_PAGES DIO_MAX_BLOCKS
#define EXT4_MAX_WRITEBACK_CREDITS DIO_CREDITS

static int ext4_da_writepages(struct address_space *mapping,
struct writeback_control *wbc)
{
return mpage_da_writepages(mapping, wbc, ext4_da_get_block_write);
struct inode *inode = mapping->host;
handle_t *handle = NULL;
int needed_blocks;
int ret = 0;
long to_write;
loff_t range_start = 0;

/*
* No pages to write? This is mainly a kludge to avoid starting
* a transaction for special inodes like journal inode on last iput()
* because that could violate lock ordering on umount
*/
if (!mapping->nrpages)
return 0;

/*
* Estimate the worse case needed credits to write out
* EXT4_MAX_BUF_BLOCKS pages
*/
needed_blocks = EXT4_MAX_WRITEBACK_CREDITS;

to_write = wbc->nr_to_write;
if (!wbc->range_cyclic) {
/*
* If range_cyclic is not set force range_cont
* and save the old writeback_index
*/
wbc->range_cont = 1;
range_start = wbc->range_start;
}

while (!ret && to_write) {
/* start a new transaction*/
handle = ext4_journal_start(inode, needed_blocks);
if (IS_ERR(handle)) {
ret = PTR_ERR(handle);
goto out_writepages;
}
/*
* set the max dirty pages could be write at a time
* to fit into the reserved transaction credits
*/
if (wbc->nr_to_write > EXT4_MAX_WRITEBACK_PAGES)
wbc->nr_to_write = EXT4_MAX_WRITEBACK_PAGES;

to_write -= wbc->nr_to_write;
ret = mpage_da_writepages(mapping, wbc,
ext4_da_get_block_write);
ext4_journal_stop(handle);
if (wbc->nr_to_write) {
/*
* There is no more writeout needed
* or we requested for a noblocking writeout
* and we found the device congested
*/
to_write += wbc->nr_to_write;
break;
}
wbc->nr_to_write = to_write;
}

out_writepages:
wbc->nr_to_write = to_write;
if (range_start)
wbc->range_start = range_start;
return ret;
}

static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
Expand Down Expand Up @@ -2137,11 +2229,6 @@ static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
return ret;
}

static int ext4_bh_unmapped_or_delay(handle_t *handle, struct buffer_head *bh)
{
return !buffer_mapped(bh) || buffer_delay(bh);
}

static int ext4_da_write_end(struct file *file,
struct address_space *mapping,
loff_t pos, unsigned len, unsigned copied,
Expand Down

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