sysfs: Simplify readdir.
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 achieved 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 remove 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.
tj: offset marker for EOF is changed from UINT_MAX to INT_MAX to avoid
overflow in case offset is 32bit.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Eric W. Biederman
Greg Kroah-Hartman
parent
94777e0918
commit
3efa65b92d
183
fs/sysfs/dir.c
183
fs/sysfs/dir.c
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@ -33,10 +33,20 @@ static DEFINE_IDA(sysfs_ino_ida);
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static void sysfs_link_sibling(struct sysfs_dirent *sd)
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{
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struct sysfs_dirent *parent_sd = sd->s_parent;
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struct sysfs_dirent **pos;
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BUG_ON(sd->s_sibling);
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sd->s_sibling = parent_sd->s_children;
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parent_sd->s_children = sd;
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/* Store directory entries in order by ino. This allows
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* readdir to properly restart without having to add a
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* cursor into the s_children list.
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*/
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for (pos = &parent_sd->s_children; *pos; pos = &(*pos)->s_sibling) {
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if (sd->s_ino < (*pos)->s_ino)
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break;
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}
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sd->s_sibling = *pos;
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*pos = sd;
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}
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/**
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@ -659,7 +669,7 @@ struct sysfs_dirent *sysfs_find_dirent(struct sysfs_dirent *parent_sd,
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struct sysfs_dirent *sd;
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for (sd = parent_sd->s_children; sd; sd = sd->s_sibling)
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if (sysfs_type(sd) && !strcmp(sd->s_name, name))
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if (!strcmp(sd->s_name, name))
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return sd;
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return NULL;
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}
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@ -811,7 +821,7 @@ static void __sysfs_remove_dir(struct sysfs_dirent *dir_sd)
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while (*pos) {
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struct sysfs_dirent *sd = *pos;
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if (sysfs_type(sd) && sysfs_type(sd) != SYSFS_DIR)
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if (sysfs_type(sd) != SYSFS_DIR)
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sysfs_remove_one(&acxt, sd);
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else
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pos = &(*pos)->s_sibling;
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@ -976,37 +986,6 @@ again:
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return error;
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}
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static int sysfs_dir_open(struct inode *inode, struct file *file)
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{
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struct dentry * dentry = file->f_path.dentry;
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struct sysfs_dirent * parent_sd = dentry->d_fsdata;
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struct sysfs_dirent * sd;
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sd = sysfs_new_dirent("_DIR_", 0, 0);
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if (sd) {
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mutex_lock(&sysfs_mutex);
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sd->s_parent = sysfs_get(parent_sd);
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sysfs_link_sibling(sd);
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mutex_unlock(&sysfs_mutex);
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}
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file->private_data = sd;
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return sd ? 0 : -ENOMEM;
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}
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static int sysfs_dir_close(struct inode *inode, struct file *file)
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{
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struct sysfs_dirent * cursor = file->private_data;
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mutex_lock(&sysfs_mutex);
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sysfs_unlink_sibling(cursor);
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mutex_unlock(&sysfs_mutex);
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release_sysfs_dirent(cursor);
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return 0;
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}
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/* Relationship between s_mode and the DT_xxx types */
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static inline unsigned char dt_type(struct sysfs_dirent *sd)
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{
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@ -1017,117 +996,51 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
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{
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struct dentry *dentry = filp->f_path.dentry;
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struct sysfs_dirent * parent_sd = dentry->d_fsdata;
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struct sysfs_dirent *cursor = filp->private_data;
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struct sysfs_dirent **pos;
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struct sysfs_dirent *pos;
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ino_t ino;
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int i = filp->f_pos;
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switch (i) {
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case 0:
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if (filp->f_pos == 0) {
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ino = parent_sd->s_ino;
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if (filldir(dirent, ".", 1, filp->f_pos, ino, DT_DIR) == 0)
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filp->f_pos++;
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}
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if (filp->f_pos == 1) {
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if (parent_sd->s_parent)
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ino = parent_sd->s_parent->s_ino;
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else
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ino = parent_sd->s_ino;
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if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
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break;
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if (filldir(dirent, "..", 2, filp->f_pos, ino, DT_DIR) == 0)
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filp->f_pos++;
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i++;
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/* fallthrough */
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case 1:
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if (parent_sd->s_parent)
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ino = parent_sd->s_parent->s_ino;
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else
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ino = parent_sd->s_ino;
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if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
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}
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if ((filp->f_pos > 1) && (filp->f_pos < INT_MAX)) {
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mutex_lock(&sysfs_mutex);
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/* Skip the dentries we have already reported */
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pos = parent_sd->s_children;
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while (pos && (filp->f_pos > pos->s_ino))
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pos = pos->s_sibling;
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for ( ; pos; pos = pos->s_sibling) {
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const char * name;
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int len;
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name = pos->s_name;
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len = strlen(name);
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filp->f_pos = ino = pos->s_ino;
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if (filldir(dirent, name, len, filp->f_pos, ino,
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dt_type(pos)) < 0)
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break;
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filp->f_pos++;
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i++;
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/* fallthrough */
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default:
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mutex_lock(&sysfs_mutex);
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pos = &parent_sd->s_children;
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while (*pos != cursor)
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pos = &(*pos)->s_sibling;
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/* unlink cursor */
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*pos = cursor->s_sibling;
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if (filp->f_pos == 2)
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pos = &parent_sd->s_children;
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for ( ; *pos; pos = &(*pos)->s_sibling) {
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struct sysfs_dirent *next = *pos;
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const char * name;
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int len;
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if (!sysfs_type(next))
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continue;
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name = next->s_name;
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len = strlen(name);
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ino = next->s_ino;
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if (filldir(dirent, name, len, filp->f_pos, ino,
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dt_type(next)) < 0)
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break;
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filp->f_pos++;
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}
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/* put cursor back in */
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cursor->s_sibling = *pos;
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*pos = cursor;
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mutex_unlock(&sysfs_mutex);
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}
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if (!pos)
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filp->f_pos = INT_MAX;
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mutex_unlock(&sysfs_mutex);
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}
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return 0;
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}
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static loff_t sysfs_dir_lseek(struct file * file, loff_t offset, int origin)
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{
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struct dentry * dentry = file->f_path.dentry;
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switch (origin) {
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case 1:
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offset += file->f_pos;
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case 0:
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if (offset >= 0)
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break;
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default:
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return -EINVAL;
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}
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if (offset != file->f_pos) {
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mutex_lock(&sysfs_mutex);
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file->f_pos = offset;
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if (file->f_pos >= 2) {
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struct sysfs_dirent *sd = dentry->d_fsdata;
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struct sysfs_dirent *cursor = file->private_data;
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struct sysfs_dirent **pos;
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loff_t n = file->f_pos - 2;
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sysfs_unlink_sibling(cursor);
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pos = &sd->s_children;
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while (n && *pos) {
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struct sysfs_dirent *next = *pos;
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if (sysfs_type(next))
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n--;
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pos = &(*pos)->s_sibling;
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}
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cursor->s_sibling = *pos;
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*pos = cursor;
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}
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mutex_unlock(&sysfs_mutex);
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}
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return offset;
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}
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const struct file_operations sysfs_dir_operations = {
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.open = sysfs_dir_open,
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.release = sysfs_dir_close,
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.llseek = sysfs_dir_lseek,
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.read = generic_read_dir,
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.readdir = sysfs_readdir,
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};
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