btrfs: fix d_off in the first dirent

Since the d_off in the first dirent for "." (that originates from the 4th argument "offset" of filldir() for the 2nd dirent for "..") is wrongly assigned in btrfs_real_readdir(), telldir returns same offset for different locations.

 | # mkfs.btrfs /dev/sdb1
 | # mount /dev/sdb1 fs0
 | # cd fs0
 | # touch file0 file1
 | # ../test
 | telldir: 0
 | readdir: d_off = 2, d_name = "."
 | telldir: 2
 | readdir: d_off = 2, d_name = ".."
 | telldir: 2
 | readdir: d_off = 3, d_name = "file0"
 | telldir: 3
 | readdir: d_off = 2147483647, d_name = "file1"
 | telldir: 2147483647

To fix this problem, pass filp->f_pos (which is loff_t) instead of the wrong constant value.

 | # ../test
 | telldir: 0
 | readdir: d_off = 1, d_name = "."
 | telldir: 1
 | readdir: d_off = 2, d_name = ".."
 | telldir: 2
 | readdir: d_off = 3, d_name = "file0"

:

At the moment the "offset" for "." is unused because there is no preceding dirent, however it is better to pass filp->f_pos to follow grammatical usage.

---
 fs/btrfs/inode.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

index 15fceef..9c1297b 100644
@@ -4125,7 +4125,8 @@ static int btrfs_real_readdir(struct file *filp, void *dirent,
 
 	/* special case for "." */
 	if (filp->f_pos == 0) {
-		over = filldir(dirent, ".", 1, 1, btrfs_ino(inode), DT_DIR);
+		over = filldir(dirent, ".", 1,
+			       filp->f_pos, inode->i_ino, DT_DIR);
 		if (over)
 			return 0;
 		filp->f_pos = 1;

@@ -4134,7 +4135,7 @@ static int btrfs_real_readdir(struct file *filp, void *dirent,
 	if (filp->f_pos == 1) {
 		u64 pino = parent_ino(filp->f_path.dentry);
 		over = filldir(dirent, "..", 2,
-			       2, pino, DT_DIR);
+			       filp->f_pos, pino, DT_DIR);
 		if (over)
 			return 0;
 		filp->f_pos = 2;

1.7.6

Wow, I made a misstep on rebase...
Here is the updated one.

Thanks,
H.Seto

=====

Since the d_off in the first dirent for "." (that originates from the 4th argument "offset" of filldir() for the 2nd dirent for "..") is wrongly assigned in btrfs_real_readdir(), telldir returns same offset for different locations.

 | # mkfs.btrfs /dev/sdb1
 | # mount /dev/sdb1 fs0
 | # cd fs0
 | # touch file0 file1
 | # ../test
 | telldir: 0
 | readdir: d_off = 2, d_name = "."
 | telldir: 2
 | readdir: d_off = 2, d_name = ".."
 | telldir: 2
 | readdir: d_off = 3, d_name = "file0"
 | telldir: 3
 | readdir: d_off = 2147483647, d_name = "file1"
 | telldir: 2147483647

To fix this problem, pass filp->f_pos (which is loff_t) instead.

 | # ../test
 | telldir: 0
 | readdir: d_off = 1, d_name = "."
 | telldir: 1
 | readdir: d_off = 2, d_name = ".."
 | telldir: 2
 | readdir: d_off = 3, d_name = "file0"

:

At the moment the "offset" for "." is unused because there is no preceding dirent, however it is better to pass filp->f_pos to follow grammatical usage.

---
 fs/btrfs/inode.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

index 15fceef..addf025 100644
@@ -4125,7 +4125,8 @@ static int btrfs_real_readdir(struct file *filp, void *dirent,
 
 	/* special case for "." */
 	if (filp->f_pos == 0) {
-		over = filldir(dirent, ".", 1, 1, btrfs_ino(inode), DT_DIR);
+		over = filldir(dirent, ".", 1,
+			       filp->f_pos, btrfs_ino(inode), DT_DIR);
 		if (over)
 			return 0;
 		filp->f_pos = 1;

@@ -4134,7 +4135,7 @@ static int btrfs_real_readdir(struct file *filp, void *dirent,
 	if (filp->f_pos == 1) {
 		u64 pino = parent_ino(filp->f_path.dentry);
 		over = filldir(dirent, "..", 2,
-			       2, pino, DT_DIR);
+			       filp->f_pos, pino, DT_DIR);
 		if (over)
 			return 0;
 		filp->f_pos = 2;

1.7.6