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mmap: add support for read only mmap()

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Add support for read only mmap().

Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
This commit is contained in:
Benjamin LaHaise
2020-07-27 17:03:51 -04:00
committed by Andy Grover
parent c98e75006e
commit 91e68b1f83
4 changed files with 88 additions and 0 deletions
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78
kmod/src/data.c
View File

@@ -1441,6 +1441,7 @@ out:
long scoutfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
{
struct inode *inode = file_inode(file);
struct scoutfs_inode_info *si = SCOUTFS_I(inode);
struct super_block *sb = inode->i_sb;
const u64 ino = scoutfs_ino(inode);
struct scoutfs_lock *lock = NULL;
@@ -1451,6 +1452,7 @@ long scoutfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
int ret;
mutex_lock(&inode->i_mutex);
mutex_lock(&si->s_i_mutex);
/* XXX support more flags */
if (mode & ~(FALLOC_FL_KEEP_SIZE)) {
@@ -1516,6 +1518,7 @@ long scoutfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
out:
scoutfs_unlock(sb, lock, SCOUTFS_LOCK_WRITE);
mutex_unlock(&si->s_i_mutex);
mutex_unlock(&inode->i_mutex);
trace_scoutfs_data_fallocate(sb, ino, mode, offset, len, ret);
@@ -1999,6 +2002,80 @@ int scoutfs_data_waiting(struct super_block *sb, u64 ino, u64 iblock,
return ret;
}
int scoutfs_data_filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
struct file *file = vma->vm_file;
struct inode *inode = file_inode(file);
struct scoutfs_inode_info *si = SCOUTFS_I(inode);
struct super_block *sb = inode->i_sb;
struct scoutfs_lock *inode_lock = NULL;
SCOUTFS_DECLARE_PER_TASK_ENTRY(pt_ent);
DECLARE_DATA_WAIT(dw);
bool have_ret = false;
loff_t pos;
int ret;
pos = vmf->pgoff;
pos <<= PAGE_CACHE_SHIFT;
retry:
ret = scoutfs_lock_inode(sb, SCOUTFS_LOCK_READ,
SCOUTFS_LKF_REFRESH_INODE, inode, &inode_lock);
if (ret < 0)
return VM_FAULT_SIGBUS;
if (scoutfs_per_task_add_excl(&si->pt_data_lock, &pt_ent, inode_lock)) {
/* protect checked extents from stage/release */
mutex_lock(&si->s_i_mutex);
atomic_inc(&inode->i_dio_count);
mutex_unlock(&si->s_i_mutex);
ret = scoutfs_data_wait_check(inode, pos, PAGE_SIZE,
SEF_OFFLINE, SCOUTFS_IOC_DWO_READ,
&dw, inode_lock);
if (ret != 0) {
goto out;
}
}
ret = filemap_fault(vma, vmf);
have_ret = true;
out:
if (scoutfs_per_task_del(&si->pt_data_lock, &pt_ent))
inode_dio_done(inode);
scoutfs_unlock(sb, inode_lock, SCOUTFS_LOCK_READ);
if (scoutfs_data_wait_found(&dw)) {
int err = scoutfs_data_wait(inode, &dw);
if (!have_ret) {
if (err == 0)
goto retry;
up_read(&vma->vm_mm->mmap_sem);
ret = VM_FAULT_RETRY;
have_ret = true;
}
}
if (!have_ret)
ret = VM_FAULT_SIGBUS;
return ret;
}
static const struct vm_operations_struct scoutfs_data_file_vm_ops = {
.fault = scoutfs_data_filemap_fault,
.remap_pages = generic_file_remap_pages,
};
static int scoutfs_file_mmap(struct file *file, struct vm_area_struct *vma)
{
if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
return -EINVAL;
file_accessed(file);
vma->vm_ops = &scoutfs_data_file_vm_ops;
return 0;
}
const struct address_space_operations scoutfs_file_aops = {
.readpage = scoutfs_readpage,
.readpages = scoutfs_readpages,
@@ -2013,6 +2090,7 @@ const struct file_operations scoutfs_file_fops = {
.write = do_sync_write,
.aio_read = scoutfs_file_aio_read,
.aio_write = scoutfs_file_aio_write,
.mmap = scoutfs_file_mmap,
.unlocked_ioctl = scoutfs_ioctl,
.fsync = scoutfs_file_fsync,
.llseek = scoutfs_file_llseek,

1
kmod/src/inode.c
View File

@@ -66,6 +66,7 @@ static void scoutfs_inode_ctor(void *obj)
{
struct scoutfs_inode_info *ci = obj;
mutex_init(&ci->s_i_mutex);
mutex_init(&ci->item_mutex);
seqcount_init(&ci->seqcount);
ci->staging = false;

6
kmod/src/inode.h
View File

@@ -28,6 +28,12 @@ struct scoutfs_inode_info {
u64 offline_blocks;
u32 flags;
/* We can't use inode->i_mutex to protect i_dio_count due to lock
* ordering in the kernel between i_mutex and mmap_sem. Use this
* as an inner lock.
*/
struct mutex s_i_mutex;
/*
* The in-memory item info caches the current index item values
* so that we can decide to update them with comparisons instead

3
kmod/src/ioctl.c
View File

@@ -268,6 +268,7 @@ out:
static long scoutfs_ioc_release(struct file *file, unsigned long arg)
{
struct inode *inode = file_inode(file);
struct scoutfs_inode_info *si = SCOUTFS_I(inode);
struct super_block *sb = inode->i_sb;
struct scoutfs_ioctl_release args;
struct scoutfs_lock *lock = NULL;
@@ -294,6 +295,7 @@ static long scoutfs_ioc_release(struct file *file, unsigned long arg)
return ret;
mutex_lock(&inode->i_mutex);
mutex_lock(&si->s_i_mutex);
ret = scoutfs_lock_inode(sb, SCOUTFS_LOCK_WRITE,
SCOUTFS_LKF_REFRESH_INODE, inode, &lock);
@@ -341,6 +343,7 @@ static long scoutfs_ioc_release(struct file *file, unsigned long arg)
out:
scoutfs_unlock(sb, lock, SCOUTFS_LOCK_WRITE);
mutex_unlock(&si->s_i_mutex);
mutex_unlock(&inode->i_mutex);
mnt_drop_write_file(file);