Commit d515afe8 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

tmpfs: no need to use i_lock 



2.6.36's 7e496299 ("tmpfs: make tmpfs scalable with percpu_counter for
used blocks") to make tmpfs scalable with percpu_counter used
inode->i_lock in place of sbinfo->stat_lock around i_blocks updates; but
that was adverse to scalability, and unnecessary, since info->lock is
already held there in the fast paths.

Remove those uses of i_lock, and add info->lock in the three error paths
where it's then needed across shmem_free_blocks().  It's not actually
needed across shmem_unacct_blocks(), but they're so often paired that it
looks wrong to split them apart.

Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Acked-by: default avatarTim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d0823576

mm/shmem.c

+6 −8
Original line number Diff line number Diff line
@@ -241,9 +241,7 @@ static void shmem_free_blocks(struct inode *inode, long pages) 
	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);

	if (sbinfo->max_blocks) {

		percpu_counter_add(&sbinfo->used_blocks, -pages);

		spin_lock(&inode->i_lock);

		inode->i_blocks -= pages*BLOCKS_PER_PAGE;

		spin_unlock(&inode->i_lock);

	}

}
@@ -432,9 +430,7 @@ static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long 
						sbinfo->max_blocks - 1) >= 0)

				return ERR_PTR(-ENOSPC);

			percpu_counter_inc(&sbinfo->used_blocks);

			spin_lock(&inode->i_lock);

			inode->i_blocks += BLOCKS_PER_PAGE;

			spin_unlock(&inode->i_lock);

		}



		spin_unlock(&info->lock);
@@ -1421,9 +1417,7 @@ repeat: 
			    shmem_acct_block(info->flags))

				goto nospace;

			percpu_counter_inc(&sbinfo->used_blocks);

			spin_lock(&inode->i_lock);

			inode->i_blocks += BLOCKS_PER_PAGE;

			spin_unlock(&inode->i_lock);

		} else if (shmem_acct_block(info->flags))

			goto nospace;
@@ -1434,8 +1428,10 @@ repeat: 
				spin_unlock(&info->lock);

				filepage = shmem_alloc_page(gfp, info, idx);

				if (!filepage) {

					spin_lock(&info->lock);

					shmem_unacct_blocks(info->flags, 1);

					shmem_free_blocks(inode, 1);

					spin_unlock(&info->lock);

					error = -ENOMEM;

					goto failed;

				}
@@ -1449,8 +1445,10 @@ repeat: 
					current->mm, GFP_KERNEL);

				if (error) {

					page_cache_release(filepage);

					spin_lock(&info->lock);

					shmem_unacct_blocks(info->flags, 1);

					shmem_free_blocks(inode, 1);

					spin_unlock(&info->lock);

					filepage = NULL;

					goto failed;

				}
@@ -1480,10 +1478,10 @@ repeat: 
			 * be done automatically.

			 */

			if (ret) {

				spin_unlock(&info->lock);

				page_cache_release(filepage);

				shmem_unacct_blocks(info->flags, 1);

				shmem_free_blocks(inode, 1);

				spin_unlock(&info->lock);

				page_cache_release(filepage);

				filepage = NULL;

				if (error)

					goto failed;

CRA Git | Maintained and supported by SUSTech CRA and CCSE