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Commit f3bd1f3f authored by Mingming Cao's avatar Mingming Cao Committed by Theodore Ts'o
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ext4: journal credits reservation fixes for DIO, fallocate 



DIO and fallocate credit calculation is different than writepage, as
they do start a new journal right for each call to ext4_get_blocks_wrap().
This patch uses the helper function in DIO and fallocate case, passing
a flag indicating that the modified data are contigous thus could account
less indirect/index blocks.

This patch also fixed the journal credit reservation for direct I/O
(DIO).  Previously the estimated credits for DIO only was calculated for
non-extent files, which was not enough if the file is extent-based.

Also fixed was fallocate double-counting credits for modifying the the
superblock.

Signed-off-by: default avatarMingming Cao <cmm@us.ibm.com>
Reviewed-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent ee12b630

fs/ext4/ext4.h

+1 −0
Original line number Diff line number Diff line
@@ -1073,6 +1073,7 @@ extern void ext4_get_inode_flags(struct ext4_inode_info *); 
extern void ext4_set_aops(struct inode *inode);

extern int ext4_writepage_trans_blocks(struct inode *);

extern int ext4_meta_trans_blocks(struct inode *, int nrblocks, int idxblocks);

extern int ext4_chunk_trans_blocks(struct inode *, int nrblocks);

extern int ext4_block_truncate_page(handle_t *handle,

		struct address_space *mapping, loff_t from);

extern int ext4_page_mkwrite(struct vm_area_struct *vma, struct page *page);

fs/ext4/extents.c

+5 −6
Original line number Diff line number Diff line
@@ -1758,7 +1758,7 @@ int ext4_ext_calc_credits_for_single_extent(struct inode *inode, int num, 
{

	if (path) {

		int depth = ext_depth(inode);

		int ret;

		int ret = 0;



		/* probably there is space in leaf? */

		if (le16_to_cpu(path[depth].p_hdr->eh_entries)
@@ -1777,7 +1777,7 @@ int ext4_ext_calc_credits_for_single_extent(struct inode *inode, int num, 
		}

	}



	return ext4_meta_trans_blocks(inode, num, 1);

	return ext4_chunk_trans_blocks(inode, num);

}



/*
@@ -2810,7 +2810,7 @@ void ext4_ext_truncate(struct inode *inode) 
	/*

	 * probably first extent we're gonna free will be last in block

	 */

	err = ext4_writepage_trans_blocks(inode) + 3;

	err = ext4_writepage_trans_blocks(inode);

	handle = ext4_journal_start(inode, err);

	if (IS_ERR(handle))

		return;
@@ -2923,10 +2923,9 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len) 
	max_blocks = (EXT4_BLOCK_ALIGN(len + offset, blkbits) >> blkbits)

							- block;

	/*

	 * credits to insert 1 extent into extent tree + buffers to be able to

	 * modify 1 super block, 1 block bitmap and 1 group descriptor.

	 * credits to insert 1 extent into extent tree

	 */

	credits = EXT4_DATA_TRANS_BLOCKS(inode->i_sb) + 3;

	credits = ext4_chunk_trans_blocks(inode, max_blocks);

	mutex_lock(&inode->i_mutex);

retry:

	while (ret >= 0 && ret < max_blocks) {

fs/ext4/inode.c

+24 −21
Original line number Diff line number Diff line
@@ -1044,18 +1044,6 @@ static void ext4_da_update_reserve_space(struct inode *inode, int used) 
	spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);

}



/* Maximum number of blocks we map for direct IO at once. */

#define DIO_MAX_BLOCKS 4096

/*

 * Number of credits we need for writing DIO_MAX_BLOCKS:

 * We need sb + group descriptor + bitmap + inode -> 4

 * For B blocks with A block pointers per block we need:

 * 1 (triple ind.) + (B/A/A + 2) (doubly ind.) + (B/A + 2) (indirect).

 * If we plug in 4096 for B and 256 for A (for 1KB block size), we get 25.

 */

#define DIO_CREDITS 25





/*

 * The ext4_get_blocks_wrap() function try to look up the requested blocks,

 * and returns if the blocks are already mapped.
@@ -1167,19 +1155,23 @@ int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block, 
	return retval;

}



/* Maximum number of blocks we map for direct IO at once. */

#define DIO_MAX_BLOCKS 4096



static int ext4_get_block(struct inode *inode, sector_t iblock,

			struct buffer_head *bh_result, int create)

{

	handle_t *handle = ext4_journal_current_handle();

	int ret = 0, started = 0;

	unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;

	int dio_credits;



	if (create && !handle) {

		/* Direct IO write... */

		if (max_blocks > DIO_MAX_BLOCKS)

			max_blocks = DIO_MAX_BLOCKS;

		handle = ext4_journal_start(inode, DIO_CREDITS +

			      2 * EXT4_QUOTA_TRANS_BLOCKS(inode->i_sb));

		dio_credits = ext4_chunk_trans_blocks(inode, max_blocks);

		handle = ext4_journal_start(inode, dio_credits);

		if (IS_ERR(handle)) {

			ret = PTR_ERR(handle);

			goto out;
@@ -2243,7 +2235,7 @@ static int ext4_da_writepage(struct page *page, 
 * for DIO, writepages, and truncate

 */

#define EXT4_MAX_WRITEBACK_PAGES      DIO_MAX_BLOCKS

#define EXT4_MAX_WRITEBACK_CREDITS    DIO_CREDITS

#define EXT4_MAX_WRITEBACK_CREDITS    25



static int ext4_da_writepages(struct address_space *mapping,

				struct writeback_control *wbc)
@@ -4441,7 +4433,8 @@ int ext4_meta_trans_blocks(struct inode *inode, int nrblocks, int chunk) 


/*

 * Calulate the total number of credits to reserve to fit

 * the modification of a single pages into a single transaction

 * the modification of a single pages into a single transaction,

 * which may include multiple chunks of block allocations.

 *

 * This could be called via ext4_write_begin() or later

 * ext4_da_writepages() in delalyed allocation case.
@@ -4449,11 +4442,6 @@ int ext4_meta_trans_blocks(struct inode *inode, int nrblocks, int chunk) 
 * In both case it's possible that we could allocating multiple

 * chunks of blocks. We need to consider the worse case, when

 * one new block per extent.

 *

 * For Direct IO and fallocate, the journal credits reservation

 * is based on one single extent allocation, so they could use

 * EXT4_DATA_TRANS_BLOCKS to get the needed credit to log a single

 * chunk of allocation needs.

 */

int ext4_writepage_trans_blocks(struct inode *inode)

{
@@ -4467,6 +4455,21 @@ int ext4_writepage_trans_blocks(struct inode *inode) 
		ret += bpp;

	return ret;

}



/*

 * Calculate the journal credits for a chunk of data modification.

 *

 * This is called from DIO, fallocate or whoever calling

 * ext4_get_blocks_wrap() to map/allocate a chunk of contigous disk blocks.

 *

 * journal buffers for data blocks are not included here, as DIO

 * and fallocate do no need to journal data buffers.

 */

int ext4_chunk_trans_blocks(struct inode *inode, int nrblocks)

{

	return ext4_meta_trans_blocks(inode, nrblocks, 1);

}



/*

 * The caller must have previously called ext4_reserve_inode_write().

 * Give this, we know that the caller already has write access to iloc->bh.