hfsplus: rework hfsplus_readdir() logic

The xfstests' test-case generic/637 fails with error:

FSTYP -- hfsplus
PLATFORM -- Linux/x86_64 hfsplus-testing-0001 6.15.0-rc4+ #8 SMP PREEMPT_DYNAMIC Thu May 1 16:43:22 PDT 2025
MKFS_OPTIONS -- /dev/loop51
MOUNT_OPTIONS -- /dev/loop51 /mnt/scratch

QA output created by 637
entries 7 and 8 have duplicate d_off 8
Found unlinked files in open dir (see xfstests-dev/results//generic/637.full for details)

Debugging of the hfsplus_readdir() logic showed this:

hfsplus: hfsplus_readdir(): 163 ctx->pos 0
hfsplus: hfsplus_readdir(): 189 ctx->pos 1
hfsplus: hfsplus_readdir(): 264 ctx->pos 2, ino 18
hfsplus: hfsplus_readdir(): 264 ctx->pos 3, ino 19
hfsplus: hfsplus_readdir(): 264 ctx->pos 4, ino 28
hfsplus: hfsplus_readdir(): 264 ctx->pos 5, ino 118
hfsplus: hfsplus_readdir(): 264 ctx->pos 6, ino 29
hfsplus: hfsplus_readdir(): 264 ctx->pos 7, ino 30
hfsplus: hfsplus_readdir(): 264 ctx->pos 8, ino 31
hfsplus: hfsplus_readdir(): 304 ctx->pos 8
hfsplus: hfsplus_unlink():420 dir->i_ino 17, inode->i_ino 28
hfsplus: hfsplus_readdir(): 141 ctx->pos 7
hfsplus: hfsplus_readdir(): 264 ctx->pos 7, ino 31
hfsplus: hfsplus_readdir(): 264 ctx->pos 8, ino 32
hfsplus: hfsplus_readdir(): 264 ctx->pos 9, ino 33

It means that hfsplus_readdir() stopped the processing of
folder's items on ctx->pos 8, then, item with ino 28 has
been deleted and hfsplus_readdir() re-started the logic
from ctx->pos 7. As a result, previous and new sets of
folder's items have overlapping values for the case of
d_off 8.

Currently, HFS+ has very complicated and fragile logic
of rd->file->f_pos correction in hfsplus_delete_cat().
This patch removes this logic and it stores the current
pos into hfsplus_readdir_data. Finally, if rd->pos == ctx->pos
then hfsplus_readdir() tries to find the position in
b-tree's node by means of hfsplus_cat_key. This position is
used to re-start the folder's content traversal.

sudo ./check generic/637
FSTYP         -- hfsplus
PLATFORM      -- Linux/x86_64 hfsplus-testing-0001 7.1.0-rc1+ #44 SMP PREEMPT_DYNAMIC Mon May  4 15:58:45 PDT 2026
MKFS_OPTIONS  -- /dev/loop51
MOUNT_OPTIONS -- /dev/loop51 /mnt/scratch

generic/637  22s ...  22s
Ran: generic/637
Passed all 1 tests

Closes: https://github.com/hfs-linux-kernel/hfs-linux-kernel/issues/198
cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
cc: Yangtao Li <frank.li@vivo.com>
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>
Link: https://lore.kernel.org/r/20260505220051.2854696-2-slava@dubeyko.com
Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>

0 files changed, 0 insertions, 0 deletions