Commit 8556e8f3 authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Theodore Ts'o
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ext4: Don't allow new groups to be added during block allocation 



After we mark the blocks in the buddy cache as allocated,
we need to ensure that we don't reinit the buddy cache until
the block bitmap is updated.  This commit achieves this by holding
the group_info alloc_semaphore till ext4_mb_release_context

Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org
parent 648f5879

fs/ext4/mballoc.c

+13 −3
Original line number Diff line number Diff line
@@ -1052,6 +1052,7 @@ static void ext4_mb_release_desc(struct ext4_buddy *e4b) 
	if (e4b->bd_buddy_page)

		page_cache_release(e4b->bd_buddy_page);

	/* Done with the buddy cache */

	if (e4b->alloc_semp)

		up_read(e4b->alloc_semp);

}
@@ -1371,7 +1372,9 @@ static void ext4_mb_use_best_found(struct ext4_allocation_context *ac, 
	get_page(ac->ac_bitmap_page);

	ac->ac_buddy_page = e4b->bd_buddy_page;

	get_page(ac->ac_buddy_page);



	/* on allocation we use ac to track the held semaphore */

	ac->alloc_semp =  e4b->alloc_semp;

	e4b->alloc_semp = NULL;

	/* store last allocated for subsequent stream allocation */

	if ((ac->ac_flags & EXT4_MB_HINT_DATA)) {

		spin_lock(&sbi->s_md_lock);
@@ -4289,6 +4292,7 @@ ext4_mb_initialize_context(struct ext4_allocation_context *ac, 
	ac->ac_pa = NULL;

	ac->ac_bitmap_page = NULL;

	ac->ac_buddy_page = NULL;

	ac->alloc_semp = NULL;

	ac->ac_lg = NULL;



	/* we have to define context: we'll we work with a file or
@@ -4469,6 +4473,8 @@ static int ext4_mb_release_context(struct ext4_allocation_context *ac) 
		}

		ext4_mb_put_pa(ac, ac->ac_sb, pa);

	}

	if (ac->alloc_semp)

		up_read(ac->alloc_semp);

	if (ac->ac_bitmap_page)

		page_cache_release(ac->ac_bitmap_page);

	if (ac->ac_buddy_page)
@@ -4569,10 +4575,14 @@ repeat: 
				ac->ac_o_ex.fe_len < ac->ac_b_ex.fe_len)

			ext4_mb_new_preallocation(ac);

	}



	if (likely(ac->ac_status == AC_STATUS_FOUND)) {

		*errp = ext4_mb_mark_diskspace_used(ac, handle, reserv_blks);

		if (*errp ==  -EAGAIN) {

			/*

			 * drop the reference that we took

			 * in ext4_mb_use_best_found

			 */

			ext4_mb_release_context(ac);

			ac->ac_b_ex.fe_group = 0;

			ac->ac_b_ex.fe_start = 0;

			ac->ac_b_ex.fe_len = 0;

fs/ext4/mballoc.h

+5 −0
Original line number Diff line number Diff line
@@ -195,6 +195,11 @@ struct ext4_allocation_context { 
	__u8 ac_op;		/* operation, for history only */

	struct page *ac_bitmap_page;

	struct page *ac_buddy_page;

	/*

	 * pointer to the held semaphore upon successful

	 * block allocation

	 */

	struct rw_semaphore *alloc_semp;

	struct ext4_prealloc_space *ac_pa;

	struct ext4_locality_group *ac_lg;

};

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