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Commit 2dcba478 authored by Jan Kara's avatar Jan Kara Committed by Theodore Ts'o
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ext4: get rid of EXT4_GET_BLOCKS_NO_LOCK flag 



When dioread_nolock mode is enabled, we grab i_data_sem in
ext4_ext_direct_IO() and therefore we need to instruct _ext4_get_block()
not to grab i_data_sem again using EXT4_GET_BLOCKS_NO_LOCK. However
holding i_data_sem over overwrite direct IO isn't needed these days. We
have exclusion against truncate / hole punching because we increase
i_dio_count under i_mutex in ext4_ext_direct_IO() so once
ext4_file_write_iter() verifies blocks are allocated & written, they are
guaranteed to stay so during the whole direct IO even after we drop
i_mutex.

So we can just remove this locking abuse and the no longer necessary
EXT4_GET_BLOCKS_NO_LOCK flag.

Signed-off-by: default avatarJan Kara <jack@suse.com>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent e74031fd

fs/ext4/ext4.h

+1 −3
Original line number Diff line number Diff line
@@ -555,10 +555,8 @@ enum { 
#define EXT4_GET_BLOCKS_NO_NORMALIZE		0x0040

	/* Request will not result in inode size update (user for fallocate) */

#define EXT4_GET_BLOCKS_KEEP_SIZE		0x0080

	/* Do not take i_data_sem locking in ext4_map_blocks */

#define EXT4_GET_BLOCKS_NO_LOCK			0x0100

	/* Convert written extents to unwritten */

#define EXT4_GET_BLOCKS_CONVERT_UNWRITTEN	0x0200

#define EXT4_GET_BLOCKS_CONVERT_UNWRITTEN	0x0100



/*

 * The bit position of these flags must not overlap with any of the

fs/ext4/inode.c

+20 −23
Original line number Diff line number Diff line
@@ -403,7 +403,6 @@ static void ext4_map_blocks_es_recheck(handle_t *handle, 
	 * out taking i_data_sem.  So at the time the unwritten extent

	 * could be converted.

	 */

	if (!(flags & EXT4_GET_BLOCKS_NO_LOCK))

	down_read(&EXT4_I(inode)->i_data_sem);

	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {

		retval = ext4_ext_map_blocks(handle, inode, map, flags &
@@ -412,7 +411,6 @@ static void ext4_map_blocks_es_recheck(handle_t *handle, 
		retval = ext4_ind_map_blocks(handle, inode, map, flags &

					     EXT4_GET_BLOCKS_KEEP_SIZE);

	}

	if (!(flags & EXT4_GET_BLOCKS_NO_LOCK))

	up_read((&EXT4_I(inode)->i_data_sem));



	/*
@@ -509,7 +507,6 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode, 
	 * Try to see if we can get the block without requesting a new

	 * file system block.

	 */

	if (!(flags & EXT4_GET_BLOCKS_NO_LOCK))

	down_read(&EXT4_I(inode)->i_data_sem);

	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {

		retval = ext4_ext_map_blocks(handle, inode, map, flags &
@@ -541,7 +538,6 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode, 
		if (ret < 0)

			retval = ret;

	}

	if (!(flags & EXT4_GET_BLOCKS_NO_LOCK))

	up_read((&EXT4_I(inode)->i_data_sem));



found:
@@ -674,7 +670,7 @@ static int _ext4_get_block(struct inode *inode, sector_t iblock, 
	map.m_lblk = iblock;

	map.m_len = bh->b_size >> inode->i_blkbits;



	if (flags && !(flags & EXT4_GET_BLOCKS_NO_LOCK) && !handle) {

	if (flags && !handle) {

		/* Direct IO write... */

		if (map.m_len > DIO_MAX_BLOCKS)

			map.m_len = DIO_MAX_BLOCKS;
@@ -879,9 +875,6 @@ int do_journal_get_write_access(handle_t *handle, 
	return ret;

}



static int ext4_get_block_write_nolock(struct inode *inode, sector_t iblock,

		   struct buffer_head *bh_result, int create);



#ifdef CONFIG_EXT4_FS_ENCRYPTION

static int ext4_block_write_begin(struct page *page, loff_t pos, unsigned len,

				  get_block_t *get_block)
@@ -3054,13 +3047,21 @@ int ext4_get_block_write(struct inode *inode, sector_t iblock, 
			       EXT4_GET_BLOCKS_IO_CREATE_EXT);

}



static int ext4_get_block_write_nolock(struct inode *inode, sector_t iblock,

static int ext4_get_block_overwrite(struct inode *inode, sector_t iblock,

		   struct buffer_head *bh_result, int create)

{

	ext4_debug("ext4_get_block_write_nolock: inode %lu, create flag %d\n",

	int ret;



	ext4_debug("ext4_get_block_overwrite: inode %lu, create flag %d\n",

		   inode->i_ino, create);

	return _ext4_get_block(inode, iblock, bh_result,

			       EXT4_GET_BLOCKS_NO_LOCK);

	ret = _ext4_get_block(inode, iblock, bh_result, 0);

	/*

	 * Blocks should have been preallocated! ext4_file_write_iter() checks

	 * that.

	 */

	WARN_ON_ONCE(!buffer_mapped(bh_result));



	return ret;

}



int ext4_get_block_dax(struct inode *inode, sector_t iblock,
@@ -3143,10 +3144,8 @@ static ssize_t ext4_ext_direct_IO(struct kiocb *iocb, struct iov_iter *iter, 
	/* If we do a overwrite dio, i_mutex locking can be released */

	overwrite = *((int *)iocb->private);



	if (overwrite) {

		down_read(&EXT4_I(inode)->i_data_sem);

	if (overwrite)

		mutex_unlock(&inode->i_mutex);

	}



	/*

	 * We could direct write to holes and fallocate.
@@ -3189,7 +3188,7 @@ static ssize_t ext4_ext_direct_IO(struct kiocb *iocb, struct iov_iter *iter, 
	}



	if (overwrite) {

		get_block_func = ext4_get_block_write_nolock;

		get_block_func = ext4_get_block_overwrite;

	} else {

		get_block_func = ext4_get_block_write;

		dio_flags = DIO_LOCKING;
@@ -3245,10 +3244,8 @@ static ssize_t ext4_ext_direct_IO(struct kiocb *iocb, struct iov_iter *iter, 
	if (iov_iter_rw(iter) == WRITE)

		inode_dio_end(inode);

	/* take i_mutex locking again if we do a ovewrite dio */

	if (overwrite) {

		up_read(&EXT4_I(inode)->i_data_sem);

	if (overwrite)

		mutex_lock(&inode->i_mutex);

	}



	return ret;

}

include/trace/events/ext4.h

+1 −2
Original line number Diff line number Diff line
@@ -42,8 +42,7 @@ struct extent_status; 
	{ EXT4_GET_BLOCKS_CONVERT,		"CONVERT" },		\

	{ EXT4_GET_BLOCKS_METADATA_NOFAIL,	"METADATA_NOFAIL" },	\

	{ EXT4_GET_BLOCKS_NO_NORMALIZE,		"NO_NORMALIZE" },	\

	{ EXT4_GET_BLOCKS_KEEP_SIZE,		"KEEP_SIZE" },		\

	{ EXT4_GET_BLOCKS_NO_LOCK,		"NO_LOCK" })

	{ EXT4_GET_BLOCKS_KEEP_SIZE,		"KEEP_SIZE" })



#define show_mflags(flags) __print_flags(flags, "",	\

	{ EXT4_MAP_NEW,		"N" },			\