The patch titled
tmpfs: no need to use i_lock
has been added to the -mm tree. Its filename is
tmpfs-no-need-to-use-i_lock.patch
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------------------------------------------------------
Subject: tmpfs: no need to use i_lock
From: Hugh Dickins <hughd@xxxxxxxxxx>
2.6.36's 7e496299d4d2 ("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: Hugh Dickins <hughd@xxxxxxxxxx>
Acked-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/shmem.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
diff -puN mm/shmem.c~tmpfs-no-need-to-use-i_lock mm/shmem.c
--- a/mm/shmem.c~tmpfs-no-need-to-use-i_lock
+++ a/mm/shmem.c
@@ -241,9 +241,7 @@ static void shmem_free_blocks(struct ino
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(stru
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;
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
mm-fix-wrong-kunmap_atomic-pointer.patch
mm-migratec-dont-account-swapcache-as-shmem.patch
linux-next.patch
mm-move-vmtruncate_range-to-truncatec.patch
mm-move-shmem-prototypes-to-shmem_fsh.patch
tmpfs-take-control-of-its-truncate_range.patch
tmpfs-add-shmem_read_mapping_page_gfp.patch
drm-ttm-use-shmem_read_mapping_page.patch
drm-i915-use-shmem_read_mapping_page.patch
drm-i915-use-shmem_truncate_range.patch
drm-i915-more-struct_mutex-locking.patch
mm-cleanup-descriptions-of-filler-arg.patch
mm-truncate-functions-are-in-truncatec.patch
mm-tidy-vmtruncate_range-and-related-functions.patch
mm-consistent-truncate-and-invalidate-loops.patch
mm-pincer-in-truncate_inode_pages_range.patch
tmpfs-no-need-to-use-i_lock.patch
prio_tree-debugging-patch.patch
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