* [PATCH v2 0/2] eventfs: Don't use dcache_readdir() for getdents()
@ 2024-01-04 1:52 Steven Rostedt
2024-01-04 1:52 ` [PATCH v2 1/2] eventfs: Remove "lookup" parameter from create_dir/file_dentry() Steven Rostedt
2024-01-04 1:52 ` [PATCH v2 2/2] eventfs: Stop using dcache_readdir() for getdents() Steven Rostedt
0 siblings, 2 replies; 3+ messages in thread
From: Steven Rostedt @ 2024-01-04 1:52 UTC (permalink / raw
To: linux-kernel, linux-trace-kernel
Cc: Masami Hiramatsu, Mark Rutland, Mathieu Desnoyers, Linus Torvalds,
Ajay Kaher, Al Viro, Christian Brauner, linux-fsdevel
After having a "pleasant" conversation with Linus over on the security
mailing list, we came to the conclusion that eventfs should not be
using the dcache_readdir() routine for iterating the entries of a
directory (getdents()).
Instead, the .open and .release callbacks of the directory file
operations was removed and all the work is now done in the .iterate_shared.
The function dcache_readdir_wrapper() was renamed to eventfs_iterate().
As the files and directories of eventfs is all known within the meta
data, it can easily supply getdents() with the information it needs without
traversing the dentry.
Changes since v1: https://lore.kernel.org/linux-trace-kernel/20240103102553.17a19cea@gandalf.local.home/
- Broke up into two patches, one to fix the lookup parameter and the
other to do the meat of the change.
- Moved the ctx->pos count up to skip creating of dentries in those cases.
Steven Rostedt (Google) (2):
eventfs: Remove "lookup" parameter from create_dir/file_dentry()
eventfs: Stop using dcache_readdir() for getdents()
----
fs/tracefs/event_inode.c | 241 ++++++++++++++++-------------------------------
1 file changed, 80 insertions(+), 161 deletions(-)
^ permalink raw reply [flat|nested] 3+ messages in thread
* [PATCH v2 1/2] eventfs: Remove "lookup" parameter from create_dir/file_dentry()
2024-01-04 1:52 [PATCH v2 0/2] eventfs: Don't use dcache_readdir() for getdents() Steven Rostedt
@ 2024-01-04 1:52 ` Steven Rostedt
2024-01-04 1:52 ` [PATCH v2 2/2] eventfs: Stop using dcache_readdir() for getdents() Steven Rostedt
1 sibling, 0 replies; 3+ messages in thread
From: Steven Rostedt @ 2024-01-04 1:52 UTC (permalink / raw
To: linux-kernel, linux-trace-kernel
Cc: Masami Hiramatsu, Mark Rutland, Mathieu Desnoyers, Linus Torvalds,
Ajay Kaher, Al Viro, Christian Brauner, linux-fsdevel
From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
The "lookup" parameter is a way to differentiate the call to
create_file/dir_dentry() from when it's just a lookup (no need to up the
dentry refcount) and accessed via a readdir (need to up the refcount).
But reality, it just makes the code more complex. Just up the refcount and
let the caller decide to dput() the result or not.
Link: https://lore.kernel.org/linux-trace-kernel/20240103102553.17a19cea@gandalf.local.home
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
fs/tracefs/event_inode.c | 55 +++++++++++++++-------------------------
1 file changed, 20 insertions(+), 35 deletions(-)
diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index f0677ea0ec24..c360300fb866 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -390,16 +390,14 @@ void eventfs_set_ei_status_free(struct tracefs_inode *ti, struct dentry *dentry)
* @mode: The mode of the file.
* @data: The data to use to set the inode of the file with on open()
* @fops: The fops of the file to be created.
- * @lookup: If called by the lookup routine, in which case, dput() the created dentry.
*
* Create a dentry for a file of an eventfs_inode @ei and place it into the
- * address located at @e_dentry. If the @e_dentry already has a dentry, then
- * just do a dget() on it and return. Otherwise create the dentry and attach it.
+ * address located at @e_dentry.
*/
static struct dentry *
create_file_dentry(struct eventfs_inode *ei, int idx,
struct dentry *parent, const char *name, umode_t mode, void *data,
- const struct file_operations *fops, bool lookup)
+ const struct file_operations *fops)
{
struct eventfs_attr *attr = NULL;
struct dentry **e_dentry = &ei->d_children[idx];
@@ -414,9 +412,7 @@ create_file_dentry(struct eventfs_inode *ei, int idx,
}
/* If the e_dentry already has a dentry, use it */
if (*e_dentry) {
- /* lookup does not need to up the ref count */
- if (!lookup)
- dget(*e_dentry);
+ dget(*e_dentry);
mutex_unlock(&eventfs_mutex);
return *e_dentry;
}
@@ -441,13 +437,12 @@ create_file_dentry(struct eventfs_inode *ei, int idx,
* way to being freed, don't return it. If e_dentry is NULL
* it means it was already freed.
*/
- if (ei->is_freed)
+ if (ei->is_freed) {
dentry = NULL;
- else
+ } else {
dentry = *e_dentry;
- /* The lookup does not need to up the dentry refcount */
- if (dentry && !lookup)
dget(dentry);
+ }
mutex_unlock(&eventfs_mutex);
return dentry;
}
@@ -465,9 +460,6 @@ create_file_dentry(struct eventfs_inode *ei, int idx,
}
mutex_unlock(&eventfs_mutex);
- if (lookup)
- dput(dentry);
-
return dentry;
}
@@ -500,13 +492,12 @@ static void eventfs_post_create_dir(struct eventfs_inode *ei)
* @pei: The eventfs_inode parent of ei.
* @ei: The eventfs_inode to create the directory for
* @parent: The dentry of the parent of this directory
- * @lookup: True if this is called by the lookup code
*
* This creates and attaches a directory dentry to the eventfs_inode @ei.
*/
static struct dentry *
create_dir_dentry(struct eventfs_inode *pei, struct eventfs_inode *ei,
- struct dentry *parent, bool lookup)
+ struct dentry *parent)
{
struct dentry *dentry = NULL;
@@ -518,11 +509,9 @@ create_dir_dentry(struct eventfs_inode *pei, struct eventfs_inode *ei,
return NULL;
}
if (ei->dentry) {
- /* If the dentry already has a dentry, use it */
+ /* If the eventfs_inode already has a dentry, use it */
dentry = ei->dentry;
- /* lookup does not need to up the ref count */
- if (!lookup)
- dget(dentry);
+ dget(dentry);
mutex_unlock(&eventfs_mutex);
return dentry;
}
@@ -542,7 +531,7 @@ create_dir_dentry(struct eventfs_inode *pei, struct eventfs_inode *ei,
* way to being freed.
*/
dentry = ei->dentry;
- if (dentry && !lookup)
+ if (dentry)
dget(dentry);
mutex_unlock(&eventfs_mutex);
return dentry;
@@ -562,9 +551,6 @@ create_dir_dentry(struct eventfs_inode *pei, struct eventfs_inode *ei,
}
mutex_unlock(&eventfs_mutex);
- if (lookup)
- dput(dentry);
-
return dentry;
}
@@ -589,8 +575,8 @@ static struct dentry *eventfs_root_lookup(struct inode *dir,
struct eventfs_inode *ei;
struct dentry *ei_dentry = NULL;
struct dentry *ret = NULL;
+ struct dentry *d;
const char *name = dentry->d_name.name;
- bool created = false;
umode_t mode;
void *data;
int idx;
@@ -626,13 +612,10 @@ static struct dentry *eventfs_root_lookup(struct inode *dir,
ret = simple_lookup(dir, dentry, flags);
if (IS_ERR(ret))
goto out;
- create_dir_dentry(ei, ei_child, ei_dentry, true);
- created = true;
- break;
- }
-
- if (created)
+ d = create_dir_dentry(ei, ei_child, ei_dentry);
+ dput(d);
goto out;
+ }
for (i = 0; i < ei->nr_entries; i++) {
entry = &ei->entries[i];
@@ -650,8 +633,8 @@ static struct dentry *eventfs_root_lookup(struct inode *dir,
ret = simple_lookup(dir, dentry, flags);
if (IS_ERR(ret))
goto out;
- create_file_dentry(ei, i, ei_dentry, name, mode, cdata,
- fops, true);
+ d = create_file_dentry(ei, i, ei_dentry, name, mode, cdata, fops);
+ dput(d);
break;
}
}
@@ -768,9 +751,10 @@ static int dcache_dir_open_wrapper(struct inode *inode, struct file *file)
inode_lock(parent->d_inode);
list_for_each_entry_srcu(ei_child, &ei->children, list,
srcu_read_lock_held(&eventfs_srcu)) {
- d = create_dir_dentry(ei, ei_child, parent, false);
+ d = create_dir_dentry(ei, ei_child, parent);
if (d) {
ret = add_dentries(&dentries, d, cnt);
+ dput(d);
if (ret < 0)
break;
cnt++;
@@ -790,9 +774,10 @@ 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, false);
+ 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++;
--
2.42.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [PATCH v2 2/2] eventfs: Stop using dcache_readdir() for getdents()
2024-01-04 1:52 [PATCH v2 0/2] eventfs: Don't use dcache_readdir() for getdents() Steven Rostedt
2024-01-04 1:52 ` [PATCH v2 1/2] eventfs: Remove "lookup" parameter from create_dir/file_dentry() Steven Rostedt
@ 2024-01-04 1:52 ` Steven Rostedt
1 sibling, 0 replies; 3+ messages in thread
From: Steven Rostedt @ 2024-01-04 1:52 UTC (permalink / raw
To: linux-kernel, linux-trace-kernel
Cc: Masami Hiramatsu, Mark Rutland, Mathieu Desnoyers, Linus Torvalds,
Ajay Kaher, Al Viro, Christian Brauner, linux-fsdevel
From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
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.
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
fs/tracefs/event_inode.c | 194 +++++++++++++--------------------------
1 file changed, 64 insertions(+), 130 deletions(-)
diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index c360300fb866..41af56f44f0a 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -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)
{
@@ -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 */
@@ -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)
@@ -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;
}
--
2.42.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
end of thread, other threads:[~2024-01-04 1:53 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2024-01-04 1:52 [PATCH v2 0/2] eventfs: Don't use dcache_readdir() for getdents() Steven Rostedt
2024-01-04 1:52 ` [PATCH v2 1/2] eventfs: Remove "lookup" parameter from create_dir/file_dentry() Steven Rostedt
2024-01-04 1:52 ` [PATCH v2 2/2] eventfs: Stop using dcache_readdir() for getdents() Steven Rostedt
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).