Commit 0830344c authored by Ojaswin Mujoo's avatar Ojaswin Mujoo Committed by Theodore Ts'o
Browse files

ext4: Abstract out overlap fix/check logic in ext4_mb_normalize_request() 



Abstract out the logic of fixing PA overlaps in ext4_mb_normalize_request
to improve readability of code. This also makes it easier to make changes
to the overlap logic in future.

There are no functional changes in this patch

Signed-off-by: default avatarOjaswin Mujoo <ojaswin@linux.ibm.com>
Reviewed-by: default avatarRitesh Harjani (IBM) <ritesh.list@gmail.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/9b35f3955a1d7b66bbd713eca1e63026e01f78c1.1679731817.git.ojaswin@linux.ibm.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 7692094a

fs/ext4/mballoc.c

+68 −41
Original line number Diff line number Diff line
@@ -4001,6 +4001,73 @@ ext4_mb_pa_assert_overlap(struct ext4_allocation_context *ac, 
	rcu_read_unlock();

}



/*

 * Given an allocation context "ac" and a range "start", "end", check

 * and adjust boundaries if the range overlaps with any of the existing

 * preallocatoins stored in the corresponding inode of the allocation context.

 *

 *Parameters:

 *	ac			allocation context

 *	start			start of the new range

 *	end			end of the new range

 */

static inline void

ext4_mb_pa_adjust_overlap(struct ext4_allocation_context *ac,

			 ext4_lblk_t *start, ext4_lblk_t *end)

{

	struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);

	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);

	struct ext4_prealloc_space *tmp_pa;

	ext4_lblk_t new_start, new_end;

	ext4_lblk_t tmp_pa_start, tmp_pa_end;



	new_start = *start;

	new_end = *end;



	/* check we don't cross already preallocated blocks */

	rcu_read_lock();

	list_for_each_entry_rcu(tmp_pa, &ei->i_prealloc_list, pa_inode_list) {

		if (tmp_pa->pa_deleted)

			continue;

		spin_lock(&tmp_pa->pa_lock);

		if (tmp_pa->pa_deleted) {

			spin_unlock(&tmp_pa->pa_lock);

			continue;

		}



		tmp_pa_start = tmp_pa->pa_lstart;

		tmp_pa_end = tmp_pa->pa_lstart + EXT4_C2B(sbi, tmp_pa->pa_len);



		/* PA must not overlap original request */

		BUG_ON(!(ac->ac_o_ex.fe_logical >= tmp_pa_end ||

			ac->ac_o_ex.fe_logical < tmp_pa_start));



		/* skip PAs this normalized request doesn't overlap with */

		if (tmp_pa_start >= new_end || tmp_pa_end <= new_start) {

			spin_unlock(&tmp_pa->pa_lock);

			continue;

		}

		BUG_ON(tmp_pa_start <= new_start && tmp_pa_end >= new_end);



		/* adjust start or end to be adjacent to this pa */

		if (tmp_pa_end <= ac->ac_o_ex.fe_logical) {

			BUG_ON(tmp_pa_end < new_start);

			new_start = tmp_pa_end;

		} else if (tmp_pa_start > ac->ac_o_ex.fe_logical) {

			BUG_ON(tmp_pa_start > new_end);

			new_end = tmp_pa_start;

		}

		spin_unlock(&tmp_pa->pa_lock);

	}

	rcu_read_unlock();



	/* XXX: extra loop to check we really don't overlap preallocations */

	ext4_mb_pa_assert_overlap(ac, new_start, new_end);



	*start = new_start;

	*end = new_end;

}



/*

 * Normalization means making request better in terms of

 * size and alignment
@@ -4016,9 +4083,6 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac, 
	loff_t size, start_off;

	loff_t orig_size __maybe_unused;

	ext4_lblk_t start;

	struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);

	struct ext4_prealloc_space *tmp_pa;

	ext4_lblk_t tmp_pa_start, tmp_pa_end;



	/* do normalize only data requests, metadata requests

	   do not need preallocation */
@@ -4119,47 +4183,10 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac, 


	end = start + size;



	/* check we don't cross already preallocated blocks */

	rcu_read_lock();

	list_for_each_entry_rcu(tmp_pa, &ei->i_prealloc_list, pa_inode_list) {

		if (tmp_pa->pa_deleted)

			continue;

		spin_lock(&tmp_pa->pa_lock);

		if (tmp_pa->pa_deleted) {

			spin_unlock(&tmp_pa->pa_lock);

			continue;

		}



		tmp_pa_start = tmp_pa->pa_lstart;

		tmp_pa_end = tmp_pa->pa_lstart + EXT4_C2B(sbi, tmp_pa->pa_len);



		/* PA must not overlap original request */

		BUG_ON(!(ac->ac_o_ex.fe_logical >= tmp_pa_end ||

			ac->ac_o_ex.fe_logical < tmp_pa_start));



		/* skip PAs this normalized request doesn't overlap with */

		if (tmp_pa_start >= end || tmp_pa_end <= start) {

			spin_unlock(&tmp_pa->pa_lock);

			continue;

		}

		BUG_ON(tmp_pa_start <= start && tmp_pa_end >= end);

	ext4_mb_pa_adjust_overlap(ac, &start, &end);



		/* adjust start or end to be adjacent to this pa */

		if (tmp_pa_end <= ac->ac_o_ex.fe_logical) {

			BUG_ON(tmp_pa_end < start);

			start = tmp_pa_end;

		} else if (tmp_pa_start > ac->ac_o_ex.fe_logical) {

			BUG_ON(tmp_pa_start > end);

			end = tmp_pa_start;

		}

		spin_unlock(&tmp_pa->pa_lock);

	}

	rcu_read_unlock();

	size = end - start;



	/* XXX: extra loop to check we really don't overlap preallocations */

	ext4_mb_pa_assert_overlap(ac, start, end);



	/*

	 * In this function "start" and "size" are normalized for better

	 * alignment and length such that we could preallocate more blocks.