Directory seek support.
Define the seek behaviour on the stored cache of dirents.
Signed-off-by: Bharata B Rao <[email protected]>
---
fs/read_write.c | 11 ---
fs/union.c | 171 +++++++++++++++++++++++++++++++++++++++++++++++++-
include/linux/fs.h | 8 ++
include/linux/union.h | 25 +++++++
4 files changed, 205 insertions(+), 10 deletions(-)
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -16,6 +16,7 @@
#include <linux/syscalls.h>
#include <linux/pagemap.h>
#include <linux/splice.h>
+#include <linux/union.h>
#include "read_write.h"
#include <asm/uaccess.h>
@@ -116,15 +117,7 @@ EXPORT_SYMBOL(default_llseek);
loff_t vfs_llseek(struct file *file, loff_t offset, int origin)
{
- loff_t (*fn)(struct file *, loff_t, int);
-
- fn = no_llseek;
- if (file->f_mode & FMODE_LSEEK) {
- fn = default_llseek;
- if (file->f_op && file->f_op->llseek)
- fn = file->f_op->llseek;
- }
- return fn(file, offset, origin);
+ return do_llseek(file, offset, origin);
}
EXPORT_SYMBOL(vfs_llseek);
--- a/fs/union.c
+++ b/fs/union.c
@@ -614,6 +614,7 @@ static int rdcache_add_entry(struct rdst
this->dtype = d_type;
INIT_LIST_HEAD(&this->list);
list_add_tail(&this->list, list);
+ r->cur_dirent = this;
return 0;
}
@@ -636,18 +637,96 @@ static int filldir_union(void *buf, cons
if (rdcache_find_entry(&r->dirent_cache, name, namlen))
return 0;
- err = cb->filldir(cb->buf, name, namlen, r->cur_off,
+ /* We come here with NULL cb->filldir from lseek path */
+ if (cb->filldir)
+ err = cb->filldir(cb->buf, name, namlen, r->cur_off,
ino, d_type);
if (err >= 0) {
rdcache_add_entry(r, &r->dirent_cache,
name, namlen, offset, ino, d_type);
r->cur_off = ++r->last_off;
r->nr_dirents++;
+ if (r->cur_off == r->fill_off) {
+ /* We filled up to the required seek offset */
+ r->fill_off = 0;
+ err = -EINVAL;
+ }
}
cb->error = err;
return err;
}
+/*
+ * This is called when current offset in rdcache gets changed and when
+ * we need to change the current underlying directory in the rdstate
+ * to match the current offset.
+ */
+static void update_rdstate(struct file *file)
+{
+ struct rdstate *r = file->f_rdstate;
+ loff_t off = r->cur_off;
+ struct union_mount *um;
+
+ if (!(r->flags & RDSTATE_NEED_UPDATE))
+ return;
+
+ spin_lock(&union_lock);
+ um = union_lookup(file->f_path.dentry, file->f_path.mnt);
+ spin_unlock(&union_lock);
+ if (!um)
+ goto out;
+ off -= um->nr_dirents;
+ path_put(&r->cur_path);
+ r->cur_path = file->f_path;
+ path_get(&r->cur_path);
+
+ while (off > 0) {
+ spin_lock(&union_lock);
+ um = union_lookup(r->cur_path.dentry, r->cur_path.mnt);
+ spin_unlock(&union_lock);
+ if (!um)
+ goto out;
+ off -= um->nr_dirents;
+ path_put(&r->cur_path);
+ r->cur_path = um->u_next;
+ path_get(&r->cur_path);
+ }
+out:
+ r->file_off = r->cur_dirent->off;
+}
+
+/*
+ * Returns dirents from rdcache to userspace.
+ */
+static int readdir_rdcache(struct file *file, struct rdcache_callback *cb)
+{
+ struct rdstate *r = cb->rdstate;
+ struct rdcache_entry *tmp = r->cur_dirent;
+ int err = 0;
+
+ BUG_ON(r->cur_off > r->last_off);
+
+ /* If offsets already uptodate, just return */
+ if (likely(r->cur_off == r->last_off))
+ return 0;
+
+ /*
+ * return the entries from cur_off till last_off from rdcache to
+ * user space.
+ */
+ list_for_each_entry_from(tmp, &r->dirent_cache, list) {
+ err = cb->filldir(cb->buf, tmp->name.name, tmp->name.len,
+ r->cur_off, tmp->ino, tmp->dtype);
+ r->cur_dirent = tmp;
+ if (err < 0)
+ break;
+ r->cur_off++;
+ r->flags |= RDSTATE_NEED_UPDATE;
+ }
+ update_rdstate(file);
+ return err;
+}
+
/* Called from last fput() */
void put_rdstate(struct rdstate *rdstate)
{
@@ -710,6 +789,10 @@ int readdir_union(struct file *file, voi
cb.rdstate = rdstate;
cb.error = 0;
+ err = readdir_rdcache(file, &cb);
+ if (err)
+ return err;
+
offset = rdstate->file_off;
/* Read from the topmost directory */
@@ -796,6 +879,92 @@ out:
return err;
}
+static void rdcache_rewind(struct file *file, struct rdstate *r, loff_t offset)
+{
+ struct rdcache_entry *tmp = r->cur_dirent;
+
+ list_for_each_entry_reverse_from(tmp, &r->dirent_cache, list) {
+ if (r->cur_off == offset)
+ break;
+ r->cur_dirent = tmp;
+ r->cur_off--;
+ r->flags |= RDSTATE_NEED_UPDATE;
+ }
+ update_rdstate(file);
+}
+
+static void rdcache_forward(struct file *file, struct rdstate *r, loff_t offset)
+{
+ struct rdcache_entry *tmp = r->cur_dirent;
+
+ list_for_each_entry_continue(tmp, &r->dirent_cache, list) {
+ if (r->cur_off == offset)
+ break;
+ r->cur_dirent = tmp;
+ r->cur_off++;
+ r->flags |= RDSTATE_NEED_UPDATE;
+ }
+ update_rdstate(file);
+}
+
+loff_t llseek_union(struct file *file, loff_t offset, int origin)
+{
+ loff_t err;
+ struct rdstate *r = file->f_rdstate;
+ loff_t orig_off = file->f_rdstate->cur_off;
+
+ if (!r)
+ return -EINVAL;
+
+ switch (origin) {
+ case SEEK_END:
+ /*
+ * To support this, we need to know the end of the directory,
+ * which may need reading _all_ the entries from the filesystem
+ * to readdir cache, which can be expensive.
+ *
+ * After we have the last entry in the cache, do
+ * offset += r->last_off;
+ */
+ err = -EINVAL;
+ goto out;
+ case SEEK_CUR:
+ offset += r->cur_off;
+ break;
+ }
+ err = -EINVAL;
+ if (offset < 0)
+ goto out;
+
+ if (offset > r->cur_off) {
+ /* Seek forward into the cache */
+ rdcache_forward(file, r, offset);
+ if (offset > r->cur_off) {
+ /*
+ * Need to seek beyond the cache, read dirents from into
+ * underlying directories into rdcache.
+ */
+ r->fill_off = offset;
+ err = readdir_union(file, NULL, NULL);
+ if (err < 0)
+ goto out;
+
+ /* readdir() failed, restore the original offset. */
+ if (offset != r->cur_off) {
+ rdcache_rewind(file, r, orig_off);
+ err = -EINVAL;
+ goto out;
+ }
+ err = offset;
+ }
+ } else {
+ rdcache_rewind(file, r, offset);
+ err = offset;
+ }
+out:
+ return err;
+}
+
/*
* Union mount copyup support
*/
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -803,9 +803,17 @@ struct rdstate {
loff_t last_off; /* Offset to last dirent in rdcache */
loff_t nr_dirents; /* Number of entries from current underlying
directory in rdcache */
+ loff_t fill_off; /* Fill cache upto this offset. Used during
+ seek */
struct list_head dirent_cache; /* cache of directory entries */
+ struct rdcache_entry *cur_dirent; /* pointer to current directory
+ entry in rdcache which corresponds to cur_off */
+ int flags;
};
+#define RDSTATE_STALE 0x01
+#define RDSTATE_NEED_UPDATE 0x02
+
extern void put_rdstate(struct rdstate *rdstate);
#else
--- a/include/linux/union.h
+++ b/include/linux/union.h
@@ -55,6 +55,7 @@ extern int attach_mnt_union(struct vfsmo
struct dentry *);
extern void detach_mnt_union(struct vfsmount *);
extern int readdir_union(struct file *, void *, filldir_t);
+extern loff_t llseek_union(struct file *, loff_t, int);
extern int last_union_is_root(struct path *);
extern int is_dir_unioned(struct path *);
extern int union_relookup_topmost(struct nameidata *, int);
@@ -110,5 +111,29 @@ static inline int do_readdir(struct file
return res;
}
+static inline loff_t do_llseek(struct file *file, loff_t offset, int origin)
+{
+ long long res;
+#ifdef CONFIG_UNION_MOUNT
+ if (IS_MNT_UNION(file->f_path.mnt) && is_dir_unioned(&file->f_path)) {
+ mutex_lock(&union_rdmutex);
+ res = llseek_union(file, offset, origin);
+ mutex_unlock(&union_rdmutex);
+ } else
+#endif
+ {
+ loff_t (*fn)(struct file *, loff_t, int);
+
+ fn = no_llseek;
+ if (file->f_mode & FMODE_LSEEK) {
+ fn = default_llseek;
+ if (file->f_op && file->f_op->llseek)
+ fn = file->f_op->llseek;
+ }
+ res = fn(file, offset, origin);
+ }
+ return res;
+}
+
#endif /* __KERNEL__ */
#endif /* __LINUX_UNION_H */
--
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