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-rw-r--r--mm/shmem.c58
1 files changed, 27 insertions, 31 deletions
diff --git a/mm/shmem.c b/mm/shmem.c
index b3db3779a30a..2275a0ff7c30 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1081,9 +1081,14 @@ static void shmem_evict_inode(struct inode *inode)
}
spin_unlock(&sbinfo->shrinklist_lock);
}
- if (!list_empty(&info->swaplist)) {
+ while (!list_empty(&info->swaplist)) {
+ /* Wait while shmem_unuse() is scanning this inode... */
+ wait_var_event(&info->stop_eviction,
+ !atomic_read(&info->stop_eviction));
mutex_lock(&shmem_swaplist_mutex);
- list_del_init(&info->swaplist);
+ /* ...but beware of the race if we peeked too early */
+ if (!atomic_read(&info->stop_eviction))
+ list_del_init(&info->swaplist);
mutex_unlock(&shmem_swaplist_mutex);
}
}
@@ -1099,10 +1104,11 @@ extern struct swap_info_struct *swap_info[];
static int shmem_find_swap_entries(struct address_space *mapping,
pgoff_t start, unsigned int nr_entries,
struct page **entries, pgoff_t *indices,
- bool frontswap)
+ unsigned int type, bool frontswap)
{
XA_STATE(xas, &mapping->i_pages, start);
struct page *page;
+ swp_entry_t entry;
unsigned int ret = 0;
if (!nr_entries)
@@ -1116,13 +1122,12 @@ static int shmem_find_swap_entries(struct address_space *mapping,
if (!xa_is_value(page))
continue;
- if (frontswap) {
- swp_entry_t entry = radix_to_swp_entry(page);
-
- if (!frontswap_test(swap_info[swp_type(entry)],
- swp_offset(entry)))
- continue;
- }
+ entry = radix_to_swp_entry(page);
+ if (swp_type(entry) != type)
+ continue;
+ if (frontswap &&
+ !frontswap_test(swap_info[type], swp_offset(entry)))
+ continue;
indices[ret] = xas.xa_index;
entries[ret] = page;
@@ -1194,7 +1199,7 @@ static int shmem_unuse_inode(struct inode *inode, unsigned int type,
pvec.nr = shmem_find_swap_entries(mapping, start, nr_entries,
pvec.pages, indices,
- frontswap);
+ type, frontswap);
if (pvec.nr == 0) {
ret = 0;
break;
@@ -1227,36 +1232,27 @@ int shmem_unuse(unsigned int type, bool frontswap,
unsigned long *fs_pages_to_unuse)
{
struct shmem_inode_info *info, *next;
- struct inode *inode;
- struct inode *prev_inode = NULL;
int error = 0;
if (list_empty(&shmem_swaplist))
return 0;
mutex_lock(&shmem_swaplist_mutex);
-
- /*
- * The extra refcount on the inode is necessary to safely dereference
- * p->next after re-acquiring the lock. New shmem inodes with swap
- * get added to the end of the list and we will scan them all.
- */
list_for_each_entry_safe(info, next, &shmem_swaplist, swaplist) {
if (!info->swapped) {
list_del_init(&info->swaplist);
continue;
}
-
- inode = igrab(&info->vfs_inode);
- if (!inode)
- continue;
-
+ /*
+ * Drop the swaplist mutex while searching the inode for swap;
+ * but before doing so, make sure shmem_evict_inode() will not
+ * remove placeholder inode from swaplist, nor let it be freed
+ * (igrab() would protect from unlink, but not from unmount).
+ */
+ atomic_inc(&info->stop_eviction);
mutex_unlock(&shmem_swaplist_mutex);
- if (prev_inode)
- iput(prev_inode);
- prev_inode = inode;
- error = shmem_unuse_inode(inode, type, frontswap,
+ error = shmem_unuse_inode(&info->vfs_inode, type, frontswap,
fs_pages_to_unuse);
cond_resched();
@@ -1264,14 +1260,13 @@ int shmem_unuse(unsigned int type, bool frontswap,
next = list_next_entry(info, swaplist);
if (!info->swapped)
list_del_init(&info->swaplist);
+ if (atomic_dec_and_test(&info->stop_eviction))
+ wake_up_var(&info->stop_eviction);
if (error)
break;
}
mutex_unlock(&shmem_swaplist_mutex);
- if (prev_inode)
- iput(prev_inode);
-
return error;
}
@@ -2238,6 +2233,7 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode
info = SHMEM_I(inode);
memset(info, 0, (char *)inode - (char *)info);
spin_lock_init(&info->lock);
+ atomic_set(&info->stop_eviction, 0);
info->seals = F_SEAL_SEAL;
info->flags = flags & VM_NORESERVE;
INIT_LIST_HEAD(&info->shrinklist);