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shmem: adapt to rhashtable-based simple_xattrs with lazy allocation

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Adapt tmpfs/shmem to use the rhashtable-based xattr path and switch
from an embedded struct to pointer-based lazy allocation.

Change shmem_inode_info.xattrs from embedded 'struct simple_xattrs' to
a pointer 'struct simple_xattrs *', initialized to NULL. This avoids
the rhashtable overhead for every tmpfs inode, which helps when a lot of
inodes exist.

The xattr store is allocated on first use:

- shmem_initxattrs(): Allocates via simple_xattrs_alloc() when
  security modules set initial xattrs during inode creation.

- shmem_xattr_handler_set(): Allocates on first setxattr, with a
  short-circuit for removal when no xattrs are stored yet.

All read paths (shmem_xattr_handler_get, shmem_listxattr) check for
NULL xattrs pointer and return -ENODATA or 0 respectively.

Replaced xattr entries are freed via simple_xattr_free_rcu() to allow
concurrent RCU readers to finish.

shmem_evict_inode() conditionally frees the xattr store only when
allocated.

Also change simple_xattr_add() from void to int to propagate
rhashtable insertion failures. shmem_initxattrs() is the only caller.

Link: https://patch.msgid.link/20260216-work-xattr-socket-v1-3-c2efa4f74cb7@kernel.org
Acked-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner
2026-02-16 14:31:59 +01:00
parent b32c4a2136
commit 52b364fed6
4 changed files with 46 additions and 28 deletions
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24
fs/xattr.c
View File

@@ -1677,19 +1677,19 @@ static bool rbtree_simple_xattr_less(struct rb_node *new_node,
* of matching xattrs is wanted. Should only be called during inode
* initialization when a few distinct initial xattrs are supposed to be set.
*/
void simple_xattr_add(struct simple_xattrs *xattrs,
struct simple_xattr *new_xattr)
int simple_xattr_add(struct simple_xattrs *xattrs,
struct simple_xattr *new_xattr)
{
if (xattrs->use_rhashtable) {
WARN_ON(rhashtable_insert_fast(&xattrs->ht,
&new_xattr->hash_node,
simple_xattr_params));
} else {
write_lock(&xattrs->lock);
rb_add(&new_xattr->rb_node, &xattrs->rb_root,
rbtree_simple_xattr_less);
write_unlock(&xattrs->lock);
}
if (xattrs->use_rhashtable)
return rhashtable_insert_fast(&xattrs->ht,
&new_xattr->hash_node,
simple_xattr_params);
write_lock(&xattrs->lock);
rb_add(&new_xattr->rb_node, &xattrs->rb_root,
rbtree_simple_xattr_less);
write_unlock(&xattrs->lock);
return 0;
}
/**

2
include/linux/shmem_fs.h
View File

@@ -48,7 +48,7 @@ struct shmem_inode_info {
};
struct timespec64 i_crtime; /* file creation time */
struct shared_policy policy; /* NUMA memory alloc policy */
struct simple_xattrs xattrs; /* list of xattrs */
struct simple_xattrs *xattrs; /* list of xattrs */
pgoff_t fallocend; /* highest fallocate endindex */
unsigned int fsflags; /* for FS_IOC_[SG]ETFLAGS */
atomic_t stop_eviction; /* hold when working on inode */

4
include/linux/xattr.h
View File

@@ -142,8 +142,8 @@ struct simple_xattr *simple_xattr_set(struct simple_xattrs *xattrs,
size_t size, int flags);
ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
char *buffer, size_t size);
void simple_xattr_add(struct simple_xattrs *xattrs,
struct simple_xattr *new_xattr);
int simple_xattr_add(struct simple_xattrs *xattrs,
struct simple_xattr *new_xattr);
int xattr_list_one(char **buffer, ssize_t *remaining_size, const char *name);
DEFINE_CLASS(simple_xattr,

44
mm/shmem.c
View File

@@ -1425,7 +1425,10 @@ static void shmem_evict_inode(struct inode *inode)
}
}
simple_xattrs_free(&info->xattrs, sbinfo->max_inodes ? &freed : NULL);
if (info->xattrs) {
simple_xattrs_free(info->xattrs, sbinfo->max_inodes ? &freed : NULL);
kfree(info->xattrs);
}
shmem_free_inode(inode->i_sb, freed);
WARN_ON(inode->i_blocks);
clear_inode(inode);
@@ -3101,7 +3104,6 @@ static struct inode *__shmem_get_inode(struct mnt_idmap *idmap,
shmem_set_inode_flags(inode, info->fsflags, NULL);
INIT_LIST_HEAD(&info->shrinklist);
INIT_LIST_HEAD(&info->swaplist);
simple_xattrs_init(&info->xattrs);
cache_no_acl(inode);
if (sbinfo->noswap)
mapping_set_unevictable(inode->i_mapping);
@@ -4255,10 +4257,13 @@ static int shmem_initxattrs(struct inode *inode,
struct shmem_inode_info *info = SHMEM_I(inode);
struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
const struct xattr *xattr;
struct simple_xattr *new_xattr;
size_t ispace = 0;
size_t len;
CLASS(simple_xattrs, xattrs)();
if (IS_ERR(xattrs))
return PTR_ERR(xattrs);
if (sbinfo->max_inodes) {
for (xattr = xattr_array; xattr->name != NULL; xattr++) {
ispace += simple_xattr_space(xattr->name,
@@ -4277,24 +4282,24 @@ static int shmem_initxattrs(struct inode *inode,
}
for (xattr = xattr_array; xattr->name != NULL; xattr++) {
new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
CLASS(simple_xattr, new_xattr)(xattr->value, xattr->value_len);
if (IS_ERR(new_xattr))
break;
len = strlen(xattr->name) + 1;
new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
GFP_KERNEL_ACCOUNT);
if (!new_xattr->name) {
kvfree(new_xattr);
if (!new_xattr->name)
break;
}
memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
XATTR_SECURITY_PREFIX_LEN);
memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
xattr->name, len);
simple_xattr_add(&info->xattrs, new_xattr);
if (simple_xattr_add(xattrs, new_xattr))
break;
retain_and_null_ptr(new_xattr);
}
if (xattr->name != NULL) {
@@ -4303,10 +4308,10 @@ static int shmem_initxattrs(struct inode *inode,
sbinfo->free_ispace += ispace;
raw_spin_unlock(&sbinfo->stat_lock);
}
simple_xattrs_free(&info->xattrs, NULL);
return -ENOMEM;
}
smp_store_release(&info->xattrs, no_free_ptr(xattrs));
return 0;
}
@@ -4315,9 +4320,14 @@ static int shmem_xattr_handler_get(const struct xattr_handler *handler,
const char *name, void *buffer, size_t size)
{
struct shmem_inode_info *info = SHMEM_I(inode);
struct simple_xattrs *xattrs;
xattrs = READ_ONCE(info->xattrs);
if (!xattrs)
return -ENODATA;
name = xattr_full_name(handler, name);
return simple_xattr_get(&info->xattrs, name, buffer, size);
return simple_xattr_get(xattrs, name, buffer, size);
}
static int shmem_xattr_handler_set(const struct xattr_handler *handler,
@@ -4328,10 +4338,16 @@ static int shmem_xattr_handler_set(const struct xattr_handler *handler,
{
struct shmem_inode_info *info = SHMEM_I(inode);
struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
struct simple_xattrs *xattrs;
struct simple_xattr *old_xattr;
size_t ispace = 0;
name = xattr_full_name(handler, name);
xattrs = simple_xattrs_lazy_alloc(&info->xattrs, value, flags);
if (IS_ERR_OR_NULL(xattrs))
return PTR_ERR(xattrs);
if (value && sbinfo->max_inodes) {
ispace = simple_xattr_space(name, size);
raw_spin_lock(&sbinfo->stat_lock);
@@ -4344,13 +4360,13 @@ static int shmem_xattr_handler_set(const struct xattr_handler *handler,
return -ENOSPC;
}
old_xattr = simple_xattr_set(&info->xattrs, name, value, size, flags);
old_xattr = simple_xattr_set(xattrs, name, value, size, flags);
if (!IS_ERR(old_xattr)) {
ispace = 0;
if (old_xattr && sbinfo->max_inodes)
ispace = simple_xattr_space(old_xattr->name,
old_xattr->size);
simple_xattr_free(old_xattr);
simple_xattr_free_rcu(old_xattr);
old_xattr = NULL;
inode_set_ctime_current(inode);
inode_inc_iversion(inode);
@@ -4391,7 +4407,9 @@ static const struct xattr_handler * const shmem_xattr_handlers[] = {
static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
{
struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
return simple_xattr_list(d_inode(dentry), &info->xattrs, buffer, size);
return simple_xattr_list(d_inode(dentry), READ_ONCE(info->xattrs),
buffer, size);
}
#endif /* CONFIG_TMPFS_XATTR */