[RFC v2 63/83] File operation: llseek.

Andiry Xu
2018-03-10T18:29:07Z

Search the file radix tree to find hold or data.

Signed-off-by: Andiry Xu <jix024@cs.ucsd.edu>
---
fs/nova/file.c | 47 +++++++++++++++++++++++
fs/nova/inode.c | 113 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
fs/nova/inode.h | 1 +
fs/nova/nova.h | 1 +
4 files changed, 162 insertions(+)

diff --git a/fs/nova/file.c b/fs/nova/file.c
index b46d4bd..ecaf20a 100644
--- a/fs/nova/file.c
+++ b/fs/nova/file.c
@@ -23,6 +23,53 @@
#include "nova.h"
#include "inode.h"

+static loff_t nova_llseek(struct file *file, loff_t offset, int origin)
+{
+ struct inode *inode = file->f_path.dentry->d_inode;
+ struct nova_inode_info *si = NOVA_I(inode);
+ struct nova_inode_info_header *sih = &si->header;
+ int retval;
+
+ if (origin != SEEK_DATA && origin != SEEK_HOLE)
+ return generic_file_llseek(file, offset, origin);
+
+ sih_lock_shared(sih);
+ switch (origin) {
+ case SEEK_DATA:
+ retval = nova_find_region(inode, &offset, 0);
+ if (retval) {
+ sih_unlock_shared(sih);
+ return retval;
+ }
+ break;
+ case SEEK_HOLE:
+ retval = nova_find_region(inode, &offset, 1);
+ if (retval) {
+ sih_unlock_shared(sih);
+ return retval;
+ }
+ break;
+ }
+
+ if ((offset < 0 && !(file->f_mode & FMODE_UNSIGNED_OFFSET)) ||
+ offset > inode->i_sb->s_maxbytes) {
+ sih_unlock_shared(sih);
+ return -ENXIO;
+ }
+
+ if (offset != file->f_pos) {
+ file->f_pos = offset;
+ file->f_version = 0;
+ }
+
+ sih_unlock_shared(sih);
+ return offset;
+}
+
+
+const struct file_operations nova_dax_file_operations = {
+ .llseek = nova_llseek,
+};

const struct inode_operations nova_file_inode_operations = {
.setattr = nova_notify_change,
diff --git a/fs/nova/inode.c b/fs/nova/inode.c
index 6fcc5e7..a6d74cb 100644
--- a/fs/nova/inode.c
+++ b/fs/nova/inode.c
@@ -193,6 +193,52 @@ static void nova_truncate_file_blocks(struct inode *inode, loff_t start,

}

+/* search the radix tree to find hole or data
+ * in the specified range
+ * Input:
+ * first_blocknr: first block in the specified range
+ * last_blocknr: last_blocknr in the specified range
+ * @data_found: indicates whether data blocks were found
+ * @hole_found: indicates whether a hole was found
+ * hole: whether we are looking for a hole or data
+ */
+static int nova_lookup_hole_in_range(struct super_block *sb,
+ struct nova_inode_info_header *sih,
+ unsigned long first_blocknr, unsigned long last_blocknr,
+ int *data_found, int *hole_found, int hole)
+{
+ struct nova_file_write_entry *entry;
+ unsigned long blocks = 0;
+ unsigned long pgoff, old_pgoff;
+
+ pgoff = first_blocknr;
+ while (pgoff <= last_blocknr) {
+ old_pgoff = pgoff;
+ entry = radix_tree_lookup(&sih->tree, pgoff);
+ if (entry) {
+ *data_found = 1;
+ if (!hole)
+ goto done;
+ pgoff++;
+ } else {
+ *hole_found = 1;
+ entry = nova_find_next_entry(sb, sih, pgoff);
+ pgoff++;
+ if (entry) {
+ pgoff = pgoff > entry->pgoff ?
+ pgoff : entry->pgoff;
+ if (pgoff > last_blocknr)
+ pgoff = last_blocknr + 1;
+ }
+ }
+
+ if (!*hole_found || !hole)
+ blocks += pgoff - old_pgoff;
+ }
+done:
+ return blocks;
+}
+
/* copy persistent state to struct inode */
static int nova_read_inode(struct super_block *sb, struct inode *inode,
u64 pi_addr)
@@ -232,6 +278,7 @@ static int nova_read_inode(struct super_block *sb, struct inode *inode,
switch (inode->i_mode & S_IFMT) {
case S_IFREG:
inode->i_op = &nova_file_inode_operations;
+ inode->i_fop = &nova_dax_file_operations;
break;
case S_IFDIR:
inode->i_op = &nova_dir_inode_operations;
@@ -929,6 +976,7 @@ struct inode *nova_new_vfs_inode(enum nova_new_inode_type type,
case TYPE_CREATE:
inode->i_op = &nova_file_inode_operations;
inode->i_mapping->a_ops = &nova_aops_dax;
+ inode->i_fop = &nova_dax_file_operations;
break;
case TYPE_MKNOD:
init_special_inode(inode, mode, rdev);
@@ -1170,6 +1218,71 @@ int nova_notify_change(struct dentry *dentry, struct iattr *attr)
return ret;
}

+/*
+ * find the file offset for SEEK_DATA/SEEK_HOLE
+ */
+unsigned long nova_find_region(struct inode *inode, loff_t *offset, int hole)
+{
+ struct nova_inode_info *si = NOVA_I(inode);
+ struct nova_inode_info_header *sih = &si->header;
+ unsigned int data_bits = blk_type_to_shift[sih->i_blk_type];
+ unsigned long first_blocknr, last_blocknr;
+ unsigned long blocks = 0, offset_in_block;
+ int data_found = 0, hole_found = 0;
+
+ if (*offset >= inode->i_size)
+ return -ENXIO;
+
+ if (!inode->i_blocks || !sih->i_size) {
+ if (hole)
+ return inode->i_size;
+ else
+ return -ENXIO;
+ }
+
+ offset_in_block = *offset & ((1UL << data_bits) - 1);
+
+ first_blocknr = *offset >> data_bits;
+ last_blocknr = inode->i_size >> data_bits;
+
+ nova_dbgv("find_region offset %llx, first_blocknr %lx, last_blocknr %lx hole %d\n",
+ *offset, first_blocknr, last_blocknr, hole);
+
+ blocks = nova_lookup_hole_in_range(inode->i_sb, sih,
+ first_blocknr, last_blocknr, &data_found, &hole_found, hole);
+
+ /* Searching data but only hole found till the end */
+ if (!hole && !data_found && hole_found)
+ return -ENXIO;
+
+ if (data_found && !hole_found) {
+ /* Searching data but we are already into them */
+ if (hole)
+ /* Searching hole but only data found, go to the end */
+ *offset = inode->i_size;
+ return 0;
+ }
+
+ /* Searching for hole, hole found and starting inside an hole */
+ if (hole && hole_found && !blocks) {
+ /* we found data after it */
+ if (!data_found)
+ /* last hole */
+ *offset = inode->i_size;
+ return 0;
+ }
+
+ if (offset_in_block) {
+ blocks--;
+ *offset += (blocks << data_bits) +
+ ((1 << data_bits) - offset_in_block);
+ } else {
+ *offset += blocks << data_bits;
+ }
+
+ return 0;
+}
+
static ssize_t nova_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
{
/* DAX does not support direct IO */
diff --git a/fs/nova/inode.h b/fs/nova/inode.h
index 48403cf..693aa90 100644
--- a/fs/nova/inode.h
+++ b/fs/nova/inode.h
@@ -264,6 +264,7 @@ int nova_delete_file_tree(struct super_block *sb,
struct nova_inode_info_header *sih, unsigned long start_blocknr,
unsigned long last_blocknr, bool delete_nvmm, bool delete_dead,
u64 epoch_id);
+unsigned long nova_find_region(struct inode *inode, loff_t *offset, int hole);
extern void nova_evict_inode(struct inode *inode);
extern int nova_write_inode(struct inode *inode, struct writeback_control *wbc);
extern void nova_dirty_inode(struct inode *inode, int flags);
diff --git a/fs/nova/nova.h b/fs/nova/nova.h
index 601e082..b2831f6 100644
--- a/fs/nova/nova.h
+++ b/fs/nova/nova.h
@@ -485,6 +485,7 @@ int nova_remove_dentry(struct dentry *dentry, int dec_link,
struct nova_inode_update *update, u64 epoch_id);

/* file.c */
+extern const struct file_operations nova_dax_file_operations;
extern const struct inode_operations nova_file_inode_operations;

/* namei.c */
--
2.7.4