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author | Ritesh Harjani <riteshh@linux.ibm.com> | 2020-05-20 08:40:32 +0200 |
---|---|---|
committer | Theodore Ts'o <tytso@mit.edu> | 2020-06-04 05:16:53 +0200 |
commit | 53f86b170dfa8d50b8b3fb1c5cf17c33b2327db2 (patch) | |
tree | d76dec5a659413307ebc463bdc4922d101071fdf | |
parent | ext4: add casefold flag to EXT4_INODE_* flags (diff) | |
download | linux-53f86b170dfa8d50b8b3fb1c5cf17c33b2327db2.tar.xz linux-53f86b170dfa8d50b8b3fb1c5cf17c33b2327db2.zip |
ext4: mballoc: add blocks to PA list under same spinlock after allocating blocks
ext4_mb_discard_preallocations() only checks for grp->bb_prealloc_list
of every group to discard the group's PA to free up the space if
allocation request fails. Consider below race:-
Process A Process B
1. allocate blocks
1. Fails block allocation from
ext4_mb_regular_allocator()
ext4_lock_group()
allocated blocks
more than ac_o_ex.fe_len
ext4_unlock_group()
2. Scans the
grp->bb_prealloc_list (under
ext4_lock_group()) and
find nothing and thus return
-ENOSPC.
2. Add the additional blocks to PA list
ext4_lock_group()
add blocks to grp->bb_prealloc_list
ext4_unlock_group()
Above race could be avoided if we add those additional blocks to
grp->bb_prealloc_list at the same time with block allocation when
ext4_lock_group() was still held.
With this discard-PA will know if there are actually any blocks which
could be freed from the PA
Signed-off-by: Ritesh Harjani <riteshh@linux.ibm.com>
Link: https://lore.kernel.org/r/a2217dd782585b42328981832e6d396abaaccb80.1589955723.git.riteshh@linux.ibm.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
-rw-r--r-- | fs/ext4/mballoc.c | 97 |
1 files changed, 62 insertions, 35 deletions
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 33a69424942c..decc5168d126 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -349,6 +349,7 @@ static void ext4_mb_generate_from_pa(struct super_block *sb, void *bitmap, ext4_group_t group); static void ext4_mb_generate_from_freelist(struct super_block *sb, void *bitmap, ext4_group_t group); +static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac); static inline void *mb_correct_addr_and_bit(int *bit, void *addr) { @@ -1701,6 +1702,14 @@ static void ext4_mb_use_best_found(struct ext4_allocation_context *ac, sbi->s_mb_last_start = ac->ac_f_ex.fe_start; spin_unlock(&sbi->s_md_lock); } + /* + * As we've just preallocated more space than + * user requested originally, we store allocated + * space in a special descriptor. + */ + if (ac->ac_o_ex.fe_len < ac->ac_b_ex.fe_len) + ext4_mb_new_preallocation(ac); + } /* @@ -1949,7 +1958,7 @@ void ext4_mb_simple_scan_group(struct ext4_allocation_context *ac, ext4_mb_use_best_found(ac, e4b); - BUG_ON(ac->ac_b_ex.fe_len != ac->ac_g_ex.fe_len); + BUG_ON(ac->ac_f_ex.fe_len != ac->ac_g_ex.fe_len); if (EXT4_SB(sb)->s_mb_stats) atomic_inc(&EXT4_SB(sb)->s_bal_2orders); @@ -3675,7 +3684,7 @@ static void ext4_mb_put_pa(struct ext4_allocation_context *ac, /* * creates new preallocated space for given inode */ -static noinline_for_stack int +static noinline_for_stack void ext4_mb_new_inode_pa(struct ext4_allocation_context *ac) { struct super_block *sb = ac->ac_sb; @@ -3688,10 +3697,9 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac) BUG_ON(ac->ac_o_ex.fe_len >= ac->ac_b_ex.fe_len); BUG_ON(ac->ac_status != AC_STATUS_FOUND); BUG_ON(!S_ISREG(ac->ac_inode->i_mode)); + BUG_ON(ac->ac_pa == NULL); - pa = kmem_cache_alloc(ext4_pspace_cachep, GFP_NOFS); - if (pa == NULL) - return -ENOMEM; + pa = ac->ac_pa; if (ac->ac_b_ex.fe_len < ac->ac_g_ex.fe_len) { int winl; @@ -3735,7 +3743,6 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac) pa->pa_pstart = ext4_grp_offs_to_block(sb, &ac->ac_b_ex); pa->pa_len = ac->ac_b_ex.fe_len; pa->pa_free = pa->pa_len; - atomic_set(&pa->pa_count, 1); spin_lock_init(&pa->pa_lock); INIT_LIST_HEAD(&pa->pa_inode_list); INIT_LIST_HEAD(&pa->pa_group_list); @@ -3755,21 +3762,17 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac) pa->pa_obj_lock = &ei->i_prealloc_lock; pa->pa_inode = ac->ac_inode; - ext4_lock_group(sb, ac->ac_b_ex.fe_group); list_add(&pa->pa_group_list, &grp->bb_prealloc_list); - ext4_unlock_group(sb, ac->ac_b_ex.fe_group); spin_lock(pa->pa_obj_lock); list_add_rcu(&pa->pa_inode_list, &ei->i_prealloc_list); spin_unlock(pa->pa_obj_lock); - - return 0; } /* * creates new preallocated space for locality group inodes belongs to */ -static noinline_for_stack int +static noinline_for_stack void ext4_mb_new_group_pa(struct ext4_allocation_context *ac) { struct super_block *sb = ac->ac_sb; @@ -3781,11 +3784,9 @@ ext4_mb_new_group_pa(struct ext4_allocation_context *ac) BUG_ON(ac->ac_o_ex.fe_len >= ac->ac_b_ex.fe_len); BUG_ON(ac->ac_status != AC_STATUS_FOUND); BUG_ON(!S_ISREG(ac->ac_inode->i_mode)); + BUG_ON(ac->ac_pa == NULL); - BUG_ON(ext4_pspace_cachep == NULL); - pa = kmem_cache_alloc(ext4_pspace_cachep, GFP_NOFS); - if (pa == NULL) - return -ENOMEM; + pa = ac->ac_pa; /* preallocation can change ac_b_ex, thus we store actually * allocated blocks for history */ @@ -3795,7 +3796,6 @@ ext4_mb_new_group_pa(struct ext4_allocation_context *ac) pa->pa_lstart = pa->pa_pstart; pa->pa_len = ac->ac_b_ex.fe_len; pa->pa_free = pa->pa_len; - atomic_set(&pa->pa_count, 1); spin_lock_init(&pa->pa_lock); INIT_LIST_HEAD(&pa->pa_inode_list); INIT_LIST_HEAD(&pa->pa_group_list); @@ -3816,26 +3816,20 @@ ext4_mb_new_group_pa(struct ext4_allocation_context *ac) pa->pa_obj_lock = &lg->lg_prealloc_lock; pa->pa_inode = NULL; - ext4_lock_group(sb, ac->ac_b_ex.fe_group); list_add(&pa->pa_group_list, &grp->bb_prealloc_list); - ext4_unlock_group(sb, ac->ac_b_ex.fe_group); /* * We will later add the new pa to the right bucket * after updating the pa_free in ext4_mb_release_context */ - return 0; } -static int ext4_mb_new_preallocation(struct ext4_allocation_context *ac) +static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac) { - int err; - if (ac->ac_flags & EXT4_MB_HINT_GROUP_ALLOC) - err = ext4_mb_new_group_pa(ac); + ext4_mb_new_group_pa(ac); else - err = ext4_mb_new_inode_pa(ac); - return err; + ext4_mb_new_inode_pa(ac); } /* @@ -4150,6 +4144,29 @@ repeat: } } +static int ext4_mb_pa_alloc(struct ext4_allocation_context *ac) +{ + struct ext4_prealloc_space *pa; + + BUG_ON(ext4_pspace_cachep == NULL); + pa = kmem_cache_zalloc(ext4_pspace_cachep, GFP_NOFS); + if (!pa) + return -ENOMEM; + atomic_set(&pa->pa_count, 1); + ac->ac_pa = pa; + return 0; +} + +static void ext4_mb_pa_free(struct ext4_allocation_context *ac) +{ + struct ext4_prealloc_space *pa = ac->ac_pa; + + BUG_ON(!pa); + ac->ac_pa = NULL; + WARN_ON(!atomic_dec_and_test(&pa->pa_count)); + kmem_cache_free(ext4_pspace_cachep, pa); +} + #ifdef CONFIG_EXT4_DEBUG static inline void ext4_mb_show_pa(struct super_block *sb) { @@ -4606,23 +4623,28 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle, if (!ext4_mb_use_preallocated(ac)) { ac->ac_op = EXT4_MB_HISTORY_ALLOC; ext4_mb_normalize_request(ac, ar); + + *errp = ext4_mb_pa_alloc(ac); + if (*errp) + goto errout; repeat: /* allocate space in core */ *errp = ext4_mb_regular_allocator(ac); - if (*errp) - goto discard_and_exit; - - /* as we've just preallocated more space than - * user requested originally, we store allocated - * space in a special descriptor */ - if (ac->ac_status == AC_STATUS_FOUND && - ac->ac_o_ex.fe_len < ac->ac_b_ex.fe_len) - *errp = ext4_mb_new_preallocation(ac); + /* + * pa allocated above is added to grp->bb_prealloc_list only + * when we were able to allocate some block i.e. when + * ac->ac_status == AC_STATUS_FOUND. + * And error from above mean ac->ac_status != AC_STATUS_FOUND + * So we have to free this pa here itself. + */ if (*errp) { - discard_and_exit: + ext4_mb_pa_free(ac); ext4_discard_allocated_blocks(ac); goto errout; } + if (ac->ac_status == AC_STATUS_FOUND && + ac->ac_o_ex.fe_len >= ac->ac_f_ex.fe_len) + ext4_mb_pa_free(ac); } if (likely(ac->ac_status == AC_STATUS_FOUND)) { *errp = ext4_mb_mark_diskspace_used(ac, handle, reserv_clstrs); @@ -4637,6 +4659,11 @@ repeat: freed = ext4_mb_discard_preallocations(sb, ac->ac_o_ex.fe_len); if (freed) goto repeat; + /* + * If block allocation fails then the pa allocated above + * needs to be freed here itself. + */ + ext4_mb_pa_free(ac); *errp = -ENOSPC; } |