ext4: Don't allow new groups to be added during block allocation From: Aneesh Kumar K.V 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: Aneesh Kumar K.V Signed-off-by: "Theodore Ts'o" Cc: stable@kernel.org --- V4 changes: USe ext4_mb_release_context to drop the page reference. That make sure we take care of update group pa. v3 changes: drop page reference and alloc_sem if we are retrying allocation fs/ext4/mballoc.c | 16 +++++++++++++--- fs/ext4/mballoc.h | 5 +++++ 2 files changed, 18 insertions(+), 3 deletions(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 56904a9..bd32d41 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -1052,7 +1052,8 @@ 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 */ - up_read(e4b->alloc_semp); + 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); @@ -4287,6 +4290,7 @@ 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 @@ -4467,6 +4471,8 @@ 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) @@ -4567,10 +4573,14 @@ 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; diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h index 95d4c7f..10a2921 100644 --- a/fs/ext4/mballoc.h +++ b/fs/ext4/mballoc.h @@ -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; };