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yangerkun authored
After we switch tmpfs dir operations from simple_dir_operations to simple_offset_dir_operations, every rename happened will fill new dentry to dest dir's maple tree(&SHMEM_I(inode)->dir_offsets->mt) with a free key starting with octx->newx_offset, and then set newx_offset equals to free key + 1. This will lead to infinite readdir combine with rename happened at the same time, which fail generic/736 in xfstests(detail show as below). 1. create 5000 files(1 2 3...) under one dir 2. call readdir(man 3 readdir) once, and get one entry 3. rename(entry, "TEMPFILE"), then rename("TEMPFILE", entry) 4. loop 2~3, until readdir return nothing or we loop too many times(tmpfs break test with the second condition) We choose the same logic what commit 9b378f6a ("btrfs: fix infinite directory reads") to fix it, record the last_index when we open dir, and do not emit the entry which index >= last_index. The file->private_data now used in offset dir can use directly to do this, and we also update the last_index when we llseek the dir file. Fixes: a2e45955 ("shmem: stable directory offsets") Signed-off-by: yangerkun <yangerkun@huawei.com> Link: https://lore.kernel.org/r/20240731043835.1828697-1-yangerkun@huawei.comReviewed-by: Chuck Lever <chuck.lever@oracle.com> [brauner: only update last_index after seek when offset is zero like Jan suggested] Signed-off-by: Christian Brauner <brauner@kernel.org>
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