linux/fs/erofs/fscache.c
Jingbo Xu 37020bbb71 erofs: fix missing xas_retry() in fscache mode
The xarray iteration only holds the RCU read lock and thus may encounter
XA_RETRY_ENTRY if there's process modifying the xarray concurrently.
This will cause oops when referring to the invalid entry.

Fix this by adding the missing xas_retry(), which will make the
iteration wind back to the root node if XA_RETRY_ENTRY is encountered.

Fixes: d435d53228 ("erofs: change to use asynchronous io for fscache readpage/readahead")
Suggested-by: David Howells <dhowells@redhat.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Jia Zhu <zhujia.zj@bytedance.com>
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Link: https://lore.kernel.org/r/20221114121943.29987-1-jefflexu@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
2022-11-14 23:48:38 +08:00

682 lines
16 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2022, Alibaba Cloud
* Copyright (C) 2022, Bytedance Inc. All rights reserved.
*/
#include <linux/fscache.h>
#include "internal.h"
static DEFINE_MUTEX(erofs_domain_list_lock);
static DEFINE_MUTEX(erofs_domain_cookies_lock);
static LIST_HEAD(erofs_domain_list);
static struct vfsmount *erofs_pseudo_mnt;
static struct netfs_io_request *erofs_fscache_alloc_request(struct address_space *mapping,
loff_t start, size_t len)
{
struct netfs_io_request *rreq;
rreq = kzalloc(sizeof(struct netfs_io_request), GFP_KERNEL);
if (!rreq)
return ERR_PTR(-ENOMEM);
rreq->start = start;
rreq->len = len;
rreq->mapping = mapping;
rreq->inode = mapping->host;
INIT_LIST_HEAD(&rreq->subrequests);
refcount_set(&rreq->ref, 1);
return rreq;
}
static void erofs_fscache_put_request(struct netfs_io_request *rreq)
{
if (!refcount_dec_and_test(&rreq->ref))
return;
if (rreq->cache_resources.ops)
rreq->cache_resources.ops->end_operation(&rreq->cache_resources);
kfree(rreq);
}
static void erofs_fscache_put_subrequest(struct netfs_io_subrequest *subreq)
{
if (!refcount_dec_and_test(&subreq->ref))
return;
erofs_fscache_put_request(subreq->rreq);
kfree(subreq);
}
static void erofs_fscache_clear_subrequests(struct netfs_io_request *rreq)
{
struct netfs_io_subrequest *subreq;
while (!list_empty(&rreq->subrequests)) {
subreq = list_first_entry(&rreq->subrequests,
struct netfs_io_subrequest, rreq_link);
list_del(&subreq->rreq_link);
erofs_fscache_put_subrequest(subreq);
}
}
static void erofs_fscache_rreq_unlock_folios(struct netfs_io_request *rreq)
{
struct netfs_io_subrequest *subreq;
struct folio *folio;
unsigned int iopos = 0;
pgoff_t start_page = rreq->start / PAGE_SIZE;
pgoff_t last_page = ((rreq->start + rreq->len) / PAGE_SIZE) - 1;
bool subreq_failed = false;
XA_STATE(xas, &rreq->mapping->i_pages, start_page);
subreq = list_first_entry(&rreq->subrequests,
struct netfs_io_subrequest, rreq_link);
subreq_failed = (subreq->error < 0);
rcu_read_lock();
xas_for_each(&xas, folio, last_page) {
unsigned int pgpos, pgend;
bool pg_failed = false;
if (xas_retry(&xas, folio))
continue;
pgpos = (folio_index(folio) - start_page) * PAGE_SIZE;
pgend = pgpos + folio_size(folio);
for (;;) {
if (!subreq) {
pg_failed = true;
break;
}
pg_failed |= subreq_failed;
if (pgend < iopos + subreq->len)
break;
iopos += subreq->len;
if (!list_is_last(&subreq->rreq_link,
&rreq->subrequests)) {
subreq = list_next_entry(subreq, rreq_link);
subreq_failed = (subreq->error < 0);
} else {
subreq = NULL;
subreq_failed = false;
}
if (pgend == iopos)
break;
}
if (!pg_failed)
folio_mark_uptodate(folio);
folio_unlock(folio);
}
rcu_read_unlock();
}
static void erofs_fscache_rreq_complete(struct netfs_io_request *rreq)
{
erofs_fscache_rreq_unlock_folios(rreq);
erofs_fscache_clear_subrequests(rreq);
erofs_fscache_put_request(rreq);
}
static void erofc_fscache_subreq_complete(void *priv,
ssize_t transferred_or_error, bool was_async)
{
struct netfs_io_subrequest *subreq = priv;
struct netfs_io_request *rreq = subreq->rreq;
if (IS_ERR_VALUE(transferred_or_error))
subreq->error = transferred_or_error;
if (atomic_dec_and_test(&rreq->nr_outstanding))
erofs_fscache_rreq_complete(rreq);
erofs_fscache_put_subrequest(subreq);
}
/*
* Read data from fscache and fill the read data into page cache described by
* @rreq, which shall be both aligned with PAGE_SIZE. @pstart describes
* the start physical address in the cache file.
*/
static int erofs_fscache_read_folios_async(struct fscache_cookie *cookie,
struct netfs_io_request *rreq, loff_t pstart)
{
enum netfs_io_source source;
struct super_block *sb = rreq->mapping->host->i_sb;
struct netfs_io_subrequest *subreq;
struct netfs_cache_resources *cres = &rreq->cache_resources;
struct iov_iter iter;
loff_t start = rreq->start;
size_t len = rreq->len;
size_t done = 0;
int ret;
atomic_set(&rreq->nr_outstanding, 1);
ret = fscache_begin_read_operation(cres, cookie);
if (ret)
goto out;
while (done < len) {
subreq = kzalloc(sizeof(struct netfs_io_subrequest),
GFP_KERNEL);
if (subreq) {
INIT_LIST_HEAD(&subreq->rreq_link);
refcount_set(&subreq->ref, 2);
subreq->rreq = rreq;
refcount_inc(&rreq->ref);
} else {
ret = -ENOMEM;
goto out;
}
subreq->start = pstart + done;
subreq->len = len - done;
subreq->flags = 1 << NETFS_SREQ_ONDEMAND;
list_add_tail(&subreq->rreq_link, &rreq->subrequests);
source = cres->ops->prepare_read(subreq, LLONG_MAX);
if (WARN_ON(subreq->len == 0))
source = NETFS_INVALID_READ;
if (source != NETFS_READ_FROM_CACHE) {
erofs_err(sb, "failed to fscache prepare_read (source %d)",
source);
ret = -EIO;
subreq->error = ret;
erofs_fscache_put_subrequest(subreq);
goto out;
}
atomic_inc(&rreq->nr_outstanding);
iov_iter_xarray(&iter, READ, &rreq->mapping->i_pages,
start + done, subreq->len);
ret = fscache_read(cres, subreq->start, &iter,
NETFS_READ_HOLE_FAIL,
erofc_fscache_subreq_complete, subreq);
if (ret == -EIOCBQUEUED)
ret = 0;
if (ret) {
erofs_err(sb, "failed to fscache_read (ret %d)", ret);
goto out;
}
done += subreq->len;
}
out:
if (atomic_dec_and_test(&rreq->nr_outstanding))
erofs_fscache_rreq_complete(rreq);
return ret;
}
static int erofs_fscache_meta_read_folio(struct file *data, struct folio *folio)
{
int ret;
struct super_block *sb = folio_mapping(folio)->host->i_sb;
struct netfs_io_request *rreq;
struct erofs_map_dev mdev = {
.m_deviceid = 0,
.m_pa = folio_pos(folio),
};
ret = erofs_map_dev(sb, &mdev);
if (ret)
goto out;
rreq = erofs_fscache_alloc_request(folio_mapping(folio),
folio_pos(folio), folio_size(folio));
if (IS_ERR(rreq)) {
ret = PTR_ERR(rreq);
goto out;
}
return erofs_fscache_read_folios_async(mdev.m_fscache->cookie,
rreq, mdev.m_pa);
out:
folio_unlock(folio);
return ret;
}
/*
* Read into page cache in the range described by (@pos, @len).
*
* On return, the caller is responsible for page unlocking if the output @unlock
* is true, or the callee will take this responsibility through netfs_io_request
* interface.
*
* The return value is the number of bytes successfully handled, or negative
* error code on failure. The only exception is that, the length of the range
* instead of the error code is returned on failure after netfs_io_request is
* allocated, so that .readahead() could advance rac accordingly.
*/
static int erofs_fscache_data_read(struct address_space *mapping,
loff_t pos, size_t len, bool *unlock)
{
struct inode *inode = mapping->host;
struct super_block *sb = inode->i_sb;
struct netfs_io_request *rreq;
struct erofs_map_blocks map;
struct erofs_map_dev mdev;
struct iov_iter iter;
size_t count;
int ret;
*unlock = true;
map.m_la = pos;
ret = erofs_map_blocks(inode, &map, EROFS_GET_BLOCKS_RAW);
if (ret)
return ret;
if (map.m_flags & EROFS_MAP_META) {
struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
erofs_blk_t blknr;
size_t offset, size;
void *src;
/* For tail packing layout, the offset may be non-zero. */
offset = erofs_blkoff(map.m_pa);
blknr = erofs_blknr(map.m_pa);
size = map.m_llen;
src = erofs_read_metabuf(&buf, sb, blknr, EROFS_KMAP);
if (IS_ERR(src))
return PTR_ERR(src);
iov_iter_xarray(&iter, READ, &mapping->i_pages, pos, PAGE_SIZE);
if (copy_to_iter(src + offset, size, &iter) != size) {
erofs_put_metabuf(&buf);
return -EFAULT;
}
iov_iter_zero(PAGE_SIZE - size, &iter);
erofs_put_metabuf(&buf);
return PAGE_SIZE;
}
if (!(map.m_flags & EROFS_MAP_MAPPED)) {
count = len;
iov_iter_xarray(&iter, READ, &mapping->i_pages, pos, count);
iov_iter_zero(count, &iter);
return count;
}
count = min_t(size_t, map.m_llen - (pos - map.m_la), len);
DBG_BUGON(!count || count % PAGE_SIZE);
mdev = (struct erofs_map_dev) {
.m_deviceid = map.m_deviceid,
.m_pa = map.m_pa,
};
ret = erofs_map_dev(sb, &mdev);
if (ret)
return ret;
rreq = erofs_fscache_alloc_request(mapping, pos, count);
if (IS_ERR(rreq))
return PTR_ERR(rreq);
*unlock = false;
erofs_fscache_read_folios_async(mdev.m_fscache->cookie,
rreq, mdev.m_pa + (pos - map.m_la));
return count;
}
static int erofs_fscache_read_folio(struct file *file, struct folio *folio)
{
bool unlock;
int ret;
DBG_BUGON(folio_size(folio) != EROFS_BLKSIZ);
ret = erofs_fscache_data_read(folio_mapping(folio), folio_pos(folio),
folio_size(folio), &unlock);
if (unlock) {
if (ret > 0)
folio_mark_uptodate(folio);
folio_unlock(folio);
}
return ret < 0 ? ret : 0;
}
static void erofs_fscache_readahead(struct readahead_control *rac)
{
struct folio *folio;
size_t len, done = 0;
loff_t start, pos;
bool unlock;
int ret, size;
if (!readahead_count(rac))
return;
start = readahead_pos(rac);
len = readahead_length(rac);
do {
pos = start + done;
ret = erofs_fscache_data_read(rac->mapping, pos,
len - done, &unlock);
if (ret <= 0)
return;
size = ret;
while (size) {
folio = readahead_folio(rac);
size -= folio_size(folio);
if (unlock) {
folio_mark_uptodate(folio);
folio_unlock(folio);
}
}
} while ((done += ret) < len);
}
static const struct address_space_operations erofs_fscache_meta_aops = {
.read_folio = erofs_fscache_meta_read_folio,
};
const struct address_space_operations erofs_fscache_access_aops = {
.read_folio = erofs_fscache_read_folio,
.readahead = erofs_fscache_readahead,
};
static void erofs_fscache_domain_put(struct erofs_domain *domain)
{
if (!domain)
return;
mutex_lock(&erofs_domain_list_lock);
if (refcount_dec_and_test(&domain->ref)) {
list_del(&domain->list);
if (list_empty(&erofs_domain_list)) {
kern_unmount(erofs_pseudo_mnt);
erofs_pseudo_mnt = NULL;
}
mutex_unlock(&erofs_domain_list_lock);
fscache_relinquish_volume(domain->volume, NULL, false);
kfree(domain->domain_id);
kfree(domain);
return;
}
mutex_unlock(&erofs_domain_list_lock);
}
static int erofs_fscache_register_volume(struct super_block *sb)
{
struct erofs_sb_info *sbi = EROFS_SB(sb);
char *domain_id = sbi->domain_id;
struct fscache_volume *volume;
char *name;
int ret = 0;
name = kasprintf(GFP_KERNEL, "erofs,%s",
domain_id ? domain_id : sbi->fsid);
if (!name)
return -ENOMEM;
volume = fscache_acquire_volume(name, NULL, NULL, 0);
if (IS_ERR_OR_NULL(volume)) {
erofs_err(sb, "failed to register volume for %s", name);
ret = volume ? PTR_ERR(volume) : -EOPNOTSUPP;
volume = NULL;
}
sbi->volume = volume;
kfree(name);
return ret;
}
static int erofs_fscache_init_domain(struct super_block *sb)
{
int err;
struct erofs_domain *domain;
struct erofs_sb_info *sbi = EROFS_SB(sb);
domain = kzalloc(sizeof(struct erofs_domain), GFP_KERNEL);
if (!domain)
return -ENOMEM;
domain->domain_id = kstrdup(sbi->domain_id, GFP_KERNEL);
if (!domain->domain_id) {
kfree(domain);
return -ENOMEM;
}
err = erofs_fscache_register_volume(sb);
if (err)
goto out;
if (!erofs_pseudo_mnt) {
erofs_pseudo_mnt = kern_mount(&erofs_fs_type);
if (IS_ERR(erofs_pseudo_mnt)) {
err = PTR_ERR(erofs_pseudo_mnt);
goto out;
}
}
domain->volume = sbi->volume;
refcount_set(&domain->ref, 1);
list_add(&domain->list, &erofs_domain_list);
sbi->domain = domain;
return 0;
out:
kfree(domain->domain_id);
kfree(domain);
return err;
}
static int erofs_fscache_register_domain(struct super_block *sb)
{
int err;
struct erofs_domain *domain;
struct erofs_sb_info *sbi = EROFS_SB(sb);
mutex_lock(&erofs_domain_list_lock);
list_for_each_entry(domain, &erofs_domain_list, list) {
if (!strcmp(domain->domain_id, sbi->domain_id)) {
sbi->domain = domain;
sbi->volume = domain->volume;
refcount_inc(&domain->ref);
mutex_unlock(&erofs_domain_list_lock);
return 0;
}
}
err = erofs_fscache_init_domain(sb);
mutex_unlock(&erofs_domain_list_lock);
return err;
}
static
struct erofs_fscache *erofs_fscache_acquire_cookie(struct super_block *sb,
char *name, bool need_inode)
{
struct fscache_volume *volume = EROFS_SB(sb)->volume;
struct erofs_fscache *ctx;
struct fscache_cookie *cookie;
int ret;
ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
if (!ctx)
return ERR_PTR(-ENOMEM);
cookie = fscache_acquire_cookie(volume, FSCACHE_ADV_WANT_CACHE_SIZE,
name, strlen(name), NULL, 0, 0);
if (!cookie) {
erofs_err(sb, "failed to get cookie for %s", name);
ret = -EINVAL;
goto err;
}
fscache_use_cookie(cookie, false);
ctx->cookie = cookie;
if (need_inode) {
struct inode *const inode = new_inode(sb);
if (!inode) {
erofs_err(sb, "failed to get anon inode for %s", name);
ret = -ENOMEM;
goto err_cookie;
}
set_nlink(inode, 1);
inode->i_size = OFFSET_MAX;
inode->i_mapping->a_ops = &erofs_fscache_meta_aops;
mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);
ctx->inode = inode;
}
return ctx;
err_cookie:
fscache_unuse_cookie(ctx->cookie, NULL, NULL);
fscache_relinquish_cookie(ctx->cookie, false);
err:
kfree(ctx);
return ERR_PTR(ret);
}
static void erofs_fscache_relinquish_cookie(struct erofs_fscache *ctx)
{
fscache_unuse_cookie(ctx->cookie, NULL, NULL);
fscache_relinquish_cookie(ctx->cookie, false);
iput(ctx->inode);
kfree(ctx->name);
kfree(ctx);
}
static
struct erofs_fscache *erofs_fscache_domain_init_cookie(struct super_block *sb,
char *name, bool need_inode)
{
int err;
struct inode *inode;
struct erofs_fscache *ctx;
struct erofs_domain *domain = EROFS_SB(sb)->domain;
ctx = erofs_fscache_acquire_cookie(sb, name, need_inode);
if (IS_ERR(ctx))
return ctx;
ctx->name = kstrdup(name, GFP_KERNEL);
if (!ctx->name) {
err = -ENOMEM;
goto out;
}
inode = new_inode(erofs_pseudo_mnt->mnt_sb);
if (!inode) {
err = -ENOMEM;
goto out;
}
ctx->domain = domain;
ctx->anon_inode = inode;
inode->i_private = ctx;
refcount_inc(&domain->ref);
return ctx;
out:
erofs_fscache_relinquish_cookie(ctx);
return ERR_PTR(err);
}
static
struct erofs_fscache *erofs_domain_register_cookie(struct super_block *sb,
char *name, bool need_inode)
{
struct inode *inode;
struct erofs_fscache *ctx;
struct erofs_domain *domain = EROFS_SB(sb)->domain;
struct super_block *psb = erofs_pseudo_mnt->mnt_sb;
mutex_lock(&erofs_domain_cookies_lock);
spin_lock(&psb->s_inode_list_lock);
list_for_each_entry(inode, &psb->s_inodes, i_sb_list) {
ctx = inode->i_private;
if (!ctx || ctx->domain != domain || strcmp(ctx->name, name))
continue;
igrab(inode);
spin_unlock(&psb->s_inode_list_lock);
mutex_unlock(&erofs_domain_cookies_lock);
return ctx;
}
spin_unlock(&psb->s_inode_list_lock);
ctx = erofs_fscache_domain_init_cookie(sb, name, need_inode);
mutex_unlock(&erofs_domain_cookies_lock);
return ctx;
}
struct erofs_fscache *erofs_fscache_register_cookie(struct super_block *sb,
char *name, bool need_inode)
{
if (EROFS_SB(sb)->domain_id)
return erofs_domain_register_cookie(sb, name, need_inode);
return erofs_fscache_acquire_cookie(sb, name, need_inode);
}
void erofs_fscache_unregister_cookie(struct erofs_fscache *ctx)
{
bool drop;
struct erofs_domain *domain;
if (!ctx)
return;
domain = ctx->domain;
if (domain) {
mutex_lock(&erofs_domain_cookies_lock);
drop = atomic_read(&ctx->anon_inode->i_count) == 1;
iput(ctx->anon_inode);
mutex_unlock(&erofs_domain_cookies_lock);
if (!drop)
return;
}
erofs_fscache_relinquish_cookie(ctx);
erofs_fscache_domain_put(domain);
}
int erofs_fscache_register_fs(struct super_block *sb)
{
int ret;
struct erofs_sb_info *sbi = EROFS_SB(sb);
struct erofs_fscache *fscache;
if (sbi->domain_id)
ret = erofs_fscache_register_domain(sb);
else
ret = erofs_fscache_register_volume(sb);
if (ret)
return ret;
/* acquired domain/volume will be relinquished in kill_sb() on error */
fscache = erofs_fscache_register_cookie(sb, sbi->fsid, true);
if (IS_ERR(fscache))
return PTR_ERR(fscache);
sbi->s_fscache = fscache;
return 0;
}
void erofs_fscache_unregister_fs(struct super_block *sb)
{
struct erofs_sb_info *sbi = EROFS_SB(sb);
erofs_fscache_unregister_cookie(sbi->s_fscache);
if (sbi->domain)
erofs_fscache_domain_put(sbi->domain);
else
fscache_relinquish_volume(sbi->volume, NULL, false);
sbi->s_fscache = NULL;
sbi->volume = NULL;
sbi->domain = NULL;
}