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eventfs: Stop using dcache_readdir() for getdents()
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The eventfs creates dynamically allocated dentries and inodes. Using the
dcache_readdir() logic for its own directory lookups requires hiding the
cursor of the dcache logic and playing games to allow the dcache_readdir()
to still have access to the cursor while the eventfs saved what it created
and what it needs to release.

Instead, just have eventfs have its own iterate_shared callback function
that will fill in the dent entries. This simplifies the code quite a bit.

Link: https://lore.kernel.org/linux-trace-kernel/20240104015435.682218477@goodmis.org

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ajay Kaher <akaher@vmware.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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@rostedt
rostedt committed Jan 4, 2024
1 parent b0f7e2d commit 493ec81
Showing 1 changed file with 64 additions and 130 deletions.
194 changes: 64 additions & 130 deletions fs/tracefs/event_inode.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -52,9 +52,7 @@ enum {
static struct dentry *eventfs_root_lookup(struct inode *dir,
struct dentry *dentry,
unsigned int flags);
static int dcache_dir_open_wrapper(struct inode *inode, struct file *file);
static int dcache_readdir_wrapper(struct file *file, struct dir_context *ctx);
static int eventfs_release(struct inode *inode, struct file *file);
static int eventfs_iterate(struct file *file, struct dir_context *ctx);

static void update_attr(struct eventfs_attr *attr, struct iattr *iattr)
{
Expand Down Expand Up @@ -148,11 +146,9 @@ static const struct inode_operations eventfs_file_inode_operations = {
};

static const struct file_operations eventfs_file_operations = {
.open = dcache_dir_open_wrapper,
.read = generic_read_dir,
.iterate_shared = dcache_readdir_wrapper,
.iterate_shared = eventfs_iterate,
.llseek = generic_file_llseek,
.release = eventfs_release,
};

/* Return the evenfs_inode of the "events" directory */
Expand Down Expand Up @@ -643,128 +639,87 @@ static struct dentry *eventfs_root_lookup(struct inode *dir,
return ret;
}

struct dentry_list {
void *cursor;
struct dentry **dentries;
};

/**
* eventfs_release - called to release eventfs file/dir
* @inode: inode to be released
* @file: file to be released (not used)
*/
static int eventfs_release(struct inode *inode, struct file *file)
{
struct tracefs_inode *ti;
struct dentry_list *dlist = file->private_data;
void *cursor;
int i;

ti = get_tracefs(inode);
if (!(ti->flags & TRACEFS_EVENT_INODE))
return -EINVAL;

if (WARN_ON_ONCE(!dlist))
return -EINVAL;

for (i = 0; dlist->dentries && dlist->dentries[i]; i++) {
dput(dlist->dentries[i]);
}

cursor = dlist->cursor;
kfree(dlist->dentries);
kfree(dlist);
file->private_data = cursor;
return dcache_dir_close(inode, file);
}

static int add_dentries(struct dentry ***dentries, struct dentry *d, int cnt)
{
struct dentry **tmp;

tmp = krealloc(*dentries, sizeof(d) * (cnt + 2), GFP_NOFS);
if (!tmp)
return -1;
tmp[cnt] = d;
tmp[cnt + 1] = NULL;
*dentries = tmp;
return 0;
}

/**
* dcache_dir_open_wrapper - eventfs open wrapper
* @inode: not used
* @file: dir to be opened (to create it's children)
*
* Used to dynamic create file/dir with-in @file, all the
* file/dir will be created. If already created then references
* will be increased
/*
* Walk the children of a eventfs_inode to fill in getdents().
*/
static int dcache_dir_open_wrapper(struct inode *inode, struct file *file)
static int eventfs_iterate(struct file *file, struct dir_context *ctx)
{
const struct file_operations *fops;
struct inode *f_inode = file_inode(file);
const struct eventfs_entry *entry;
struct eventfs_inode *ei_child;
struct tracefs_inode *ti;
struct eventfs_inode *ei;
struct dentry_list *dlist;
struct dentry **dentries = NULL;
struct dentry *parent = file_dentry(file);
struct dentry *d;
struct inode *f_inode = file_inode(file);
const char *name = parent->d_name.name;
struct dentry *ei_dentry = NULL;
struct dentry *dentry;
const char *name;
umode_t mode;
void *data;
int cnt = 0;
int idx;
int ret;
int i;
int r;
int ret = -EINVAL;
int ino;
int i, r, c;

if (!dir_emit_dots(file, ctx))
return 0;

ti = get_tracefs(f_inode);
if (!(ti->flags & TRACEFS_EVENT_INODE))
return -EINVAL;

if (WARN_ON_ONCE(file->private_data))
return -EINVAL;
c = ctx->pos - 2;

idx = srcu_read_lock(&eventfs_srcu);

mutex_lock(&eventfs_mutex);
ei = READ_ONCE(ti->private);
if (ei && !ei->is_freed)
ei_dentry = READ_ONCE(ei->dentry);
mutex_unlock(&eventfs_mutex);

if (!ei) {
srcu_read_unlock(&eventfs_srcu, idx);
return -EINVAL;
}


data = ei->data;
if (!ei || !ei_dentry)
goto out;

dlist = kmalloc(sizeof(*dlist), GFP_KERNEL);
if (!dlist) {
srcu_read_unlock(&eventfs_srcu, idx);
return -ENOMEM;
}
ret = 0;

inode_lock(parent->d_inode);
/*
* Need to create the dentries and inodes to have a consistent
* inode number.
*/
list_for_each_entry_srcu(ei_child, &ei->children, list,
srcu_read_lock_held(&eventfs_srcu)) {
d = create_dir_dentry(ei, ei_child, parent);
if (d) {
ret = add_dentries(&dentries, d, cnt);
dput(d);
if (ret < 0)
break;
cnt++;

if (c > 0) {
c--;
continue;
}

if (ei_child->is_freed)
continue;

name = ei_child->name;

dentry = create_dir_dentry(ei, ei_child, ei_dentry);
if (!dentry)
goto out;
ino = dentry->d_inode->i_ino;
dput(dentry);

if (!dir_emit(ctx, name, strlen(name), ino, DT_DIR))
goto out;
ctx->pos++;
}

for (i = 0; i < ei->nr_entries; i++) {
void *cdata = data;
void *cdata = ei->data;

if (c > 0) {
c--;
continue;
}

entry = &ei->entries[i];
name = entry->name;

mutex_lock(&eventfs_mutex);
/* If ei->is_freed, then the event itself may be too */
if (!ei->is_freed)
Expand All @@ -774,42 +729,21 @@ static int dcache_dir_open_wrapper(struct inode *inode, struct file *file)
mutex_unlock(&eventfs_mutex);
if (r <= 0)
continue;
d = create_file_dentry(ei, i, parent, name, mode, cdata, fops);
if (d) {
ret = add_dentries(&dentries, d, cnt);
dput(d);
if (ret < 0)
break;
cnt++;
}
}
inode_unlock(parent->d_inode);
srcu_read_unlock(&eventfs_srcu, idx);
ret = dcache_dir_open(inode, file);

/*
* dcache_dir_open() sets file->private_data to a dentry cursor.
* Need to save that but also save all the dentries that were
* opened by this function.
*/
dlist->cursor = file->private_data;
dlist->dentries = dentries;
file->private_data = dlist;
return ret;
}
dentry = create_file_dentry(ei, i, ei_dentry, name, mode, cdata, fops);
if (!dentry)
goto out;
ino = dentry->d_inode->i_ino;
dput(dentry);

/*
* This just sets the file->private_data back to the cursor and back.
*/
static int dcache_readdir_wrapper(struct file *file, struct dir_context *ctx)
{
struct dentry_list *dlist = file->private_data;
int ret;
if (!dir_emit(ctx, name, strlen(name), ino, DT_REG))
goto out;
ctx->pos++;
}
ret = 1;
out:
srcu_read_unlock(&eventfs_srcu, idx);

file->private_data = dlist->cursor;
ret = dcache_readdir(file, ctx);
dlist->cursor = file->private_data;
file->private_data = dlist;
return ret;
}

Expand Down

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