[Devel] [PATCH 13/14] sysfs: Simplify readdir.
Eric W. Biederman
ebiederm at xmission.com
Tue Jul 31 03:42:02 PDT 2007
At some point someone wrote sysfs_readdir to insert a cursor
into the list of sysfs_dirents to ensure that sysfs_readdir would
restart properly. That works but it is complex code and tends
to be expensive.
The same effect can be achived by keeping the sysfs_dirents in
inode order and using the inode number as the f_pos. Then
when we restart we just have to find the first dirent whose inode
number is equal or greater then the last sysfs_dirent we attempted
to return.
Removing the sysfs directory cursor also allows the removal of
all of the mysterious checks for sysfs_type(sd) != 0. Which
were nonbovious checks to see if a cursor was in a directory list.
Signed-off-by: Eric W. Biederman <ebiederm at xmission.com>
---
fs/sysfs/dir.c | 178 ++++++++++++++----------------------------------------
fs/sysfs/inode.c | 2 -
2 files changed, 45 insertions(+), 135 deletions(-)
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 1611cbd..f9be856 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -35,10 +35,20 @@ static void sysfs_attach_dentry(struct sysfs_dirent *sd, struct dentry *dentry);
void sysfs_link_sibling(struct sysfs_dirent *sd)
{
struct sysfs_dirent *parent_sd = sd->s_parent;
+ struct sysfs_dirent **pos;
BUG_ON(sd->s_sibling);
- sd->s_sibling = parent_sd->s_children;
- parent_sd->s_children = sd;
+
+ /* Store directory entries in order by ino. This allows
+ * readdir to properly restart without having to add a
+ * cursor into the s_children list.
+ */
+ for (pos = &parent_sd->s_children; *pos; pos = &(*pos)->s_sibling) {
+ if (sd->s_ino < (*pos)->s_ino)
+ break;
+ }
+ sd->s_sibling = *pos;
+ *pos = sd;
}
/**
@@ -590,7 +600,7 @@ struct sysfs_dirent *sysfs_find_dirent(struct sysfs_dirent *parent_sd,
struct sysfs_dirent *sd;
for (sd = parent_sd->s_children; sd; sd = sd->s_sibling)
- if (sysfs_type(sd) && !strcmp(sd->s_name, name))
+ if (!strcmp(sd->s_name, name))
return sd;
return NULL;
}
@@ -696,8 +706,7 @@ static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
goto out;
for (sd = parent_sd->s_children; sd; sd = sd->s_sibling) {
- if (sysfs_type(sd) &&
- !strcmp(sd->s_name, dentry->d_name.name))
+ if (!strcmp(sd->s_name, dentry->d_name.name))
break;
}
@@ -756,7 +765,7 @@ static void __sysfs_remove_dir(struct sysfs_dirent *dir_sd)
while (*pos) {
struct sysfs_dirent *sd = *pos;
- if (sysfs_type(sd) && sysfs_type(sd) != SYSFS_DIR) {
+ if (sysfs_type(sd) != SYSFS_DIR) {
*pos = sd->s_sibling;
sd->s_sibling = NULL;
sysfs_remove_one(&acxt, sd);
@@ -913,37 +922,6 @@ again:
return error;
}
-static int sysfs_dir_open(struct inode *inode, struct file *file)
-{
- struct dentry * dentry = file->f_path.dentry;
- struct sysfs_dirent * parent_sd = dentry->d_fsdata;
- struct sysfs_dirent * sd;
-
- sd = sysfs_new_dirent("_DIR_", 0, 0);
- if (sd) {
- mutex_lock(&sysfs_mutex);
- sd->s_parent = sysfs_get(parent_sd);
- sysfs_link_sibling(sd);
- mutex_unlock(&sysfs_mutex);
- }
-
- file->private_data = sd;
- return sd ? 0 : -ENOMEM;
-}
-
-static int sysfs_dir_close(struct inode *inode, struct file *file)
-{
- struct sysfs_dirent * cursor = file->private_data;
-
- mutex_lock(&sysfs_mutex);
- sysfs_unlink_sibling(cursor);
- mutex_unlock(&sysfs_mutex);
-
- release_sysfs_dirent(cursor);
-
- return 0;
-}
-
/* Relationship between s_mode and the DT_xxx types */
static inline unsigned char dt_type(struct sysfs_dirent *sd)
{
@@ -954,117 +932,51 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
{
struct dentry *dentry = filp->f_path.dentry;
struct sysfs_dirent * parent_sd = dentry->d_fsdata;
- struct sysfs_dirent *cursor = filp->private_data;
- struct sysfs_dirent **pos;
+ struct sysfs_dirent *pos;
ino_t ino;
- int i = filp->f_pos;
- switch (i) {
- case 0:
- ino = parent_sd->s_ino;
- if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
- break;
+ if (filp->f_pos == 0) {
+ ino = parent_sd->s_ino;
+ if (filldir(dirent, ".", 1, filp->f_pos, ino, DT_DIR) == 0)
filp->f_pos++;
- i++;
- /* fallthrough */
- case 1:
- if (parent_sd->s_parent)
- ino = parent_sd->s_parent->s_ino;
- else
- ino = parent_sd->s_ino;
- if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
- break;
+ }
+ if (filp->f_pos == 1) {
+ if (parent_sd->s_parent)
+ ino = parent_sd->s_parent->s_ino;
+ else
+ ino = parent_sd->s_ino;
+ if (filldir(dirent, "..", 2, filp->f_pos, ino, DT_DIR) == 0)
filp->f_pos++;
- i++;
- /* fallthrough */
- default:
- mutex_lock(&sysfs_mutex);
-
- pos = &parent_sd->s_children;
- while (*pos != cursor)
- pos = &(*pos)->s_sibling;
-
- /* unlink cursor */
- *pos = cursor->s_sibling;
-
- if (filp->f_pos == 2)
- pos = &parent_sd->s_children;
-
- for ( ; *pos; pos = &(*pos)->s_sibling) {
- struct sysfs_dirent *next = *pos;
- const char * name;
- int len;
-
- if (!sysfs_type(next))
- continue;
-
- name = next->s_name;
- len = strlen(name);
- ino = next->s_ino;
-
- if (filldir(dirent, name, len, filp->f_pos, ino,
- dt_type(next)) < 0)
- break;
-
- filp->f_pos++;
- }
+ }
+ if ((filp->f_pos > 1) && (filp->f_pos < UINT_MAX)) {
+ mutex_lock(&sysfs_mutex);
- /* put cursor back in */
- cursor->s_sibling = *pos;
- *pos = cursor;
+ /* Skip the dentries we have already reported */
+ pos = parent_sd->s_children;
+ while (pos && (filp->f_pos > pos->s_ino))
+ pos = pos->s_sibling;
- mutex_unlock(&sysfs_mutex);
- }
- return 0;
-}
+ for ( ; pos; pos = pos->s_sibling) {
+ const char * name;
+ int len;
-static loff_t sysfs_dir_lseek(struct file * file, loff_t offset, int origin)
-{
- struct dentry * dentry = file->f_path.dentry;
+ name = pos->s_name;
+ len = strlen(name);
+ filp->f_pos = ino = pos->s_ino;
- switch (origin) {
- case 1:
- offset += file->f_pos;
- case 0:
- if (offset >= 0)
+ if (filldir(dirent, name, len, filp->f_pos, ino,
+ dt_type(pos)) < 0)
break;
- default:
- return -EINVAL;
- }
- if (offset != file->f_pos) {
- mutex_lock(&sysfs_mutex);
-
- file->f_pos = offset;
- if (file->f_pos >= 2) {
- struct sysfs_dirent *sd = dentry->d_fsdata;
- struct sysfs_dirent *cursor = file->private_data;
- struct sysfs_dirent **pos;
- loff_t n = file->f_pos - 2;
-
- sysfs_unlink_sibling(cursor);
-
- pos = &sd->s_children;
- while (n && *pos) {
- struct sysfs_dirent *next = *pos;
- if (sysfs_type(next))
- n--;
- pos = &(*pos)->s_sibling;
- }
-
- cursor->s_sibling = *pos;
- *pos = cursor;
}
-
+ if (!pos)
+ filp->f_pos = UINT_MAX;
mutex_unlock(&sysfs_mutex);
}
-
- return offset;
+ return 0;
}
+
const struct file_operations sysfs_dir_operations = {
- .open = sysfs_dir_open,
- .release = sysfs_dir_close,
- .llseek = sysfs_dir_lseek,
.read = generic_read_dir,
.readdir = sysfs_readdir,
};
diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index f55d9da..e212c69 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -225,8 +225,6 @@ int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name)
for (pos = &dir_sd->s_children; *pos; pos = &(*pos)->s_sibling) {
sd = *pos;
- if (!sysfs_type(sd))
- continue;
if (!strcmp(sd->s_name, name)) {
*pos = sd->s_sibling;
sd->s_sibling = NULL;
--
1.5.1.1.181.g2de0
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