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2dcf5fde6d
For files with logical blocks close to EXT_MAX_BLOCKS, the file size
predicted in ext4_mb_normalize_request() may exceed EXT_MAX_BLOCKS.
This can cause some blocks to be preallocated that will not be used.
And after [Fixes], the following issue may be triggered:
=========================================================
kernel BUG at fs/ext4/mballoc.c:4653!
Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
CPU: 1 PID: 2357 Comm: xfs_io 6.7.0-rc2-00195-g0f5cc96c367f
Hardware name: linux,dummy-virt (DT)
pc : ext4_mb_use_inode_pa+0x148/0x208
lr : ext4_mb_use_inode_pa+0x98/0x208
Call trace:
ext4_mb_use_inode_pa+0x148/0x208
ext4_mb_new_inode_pa+0x240/0x4a8
ext4_mb_use_best_found+0x1d4/0x208
ext4_mb_try_best_found+0xc8/0x110
ext4_mb_regular_allocator+0x11c/0xf48
ext4_mb_new_blocks+0x790/0xaa8
ext4_ext_map_blocks+0x7cc/0xd20
ext4_map_blocks+0x170/0x600
ext4_iomap_begin+0x1c0/0x348
=========================================================
Here is a calculation when adjusting ac_b_ex in ext4_mb_new_inode_pa():
ex.fe_logical = orig_goal_end - EXT4_C2B(sbi, ex.fe_len);
if (ac->ac_o_ex.fe_logical >= ex.fe_logical)
goto adjust_bex;
The problem is that when orig_goal_end is subtracted from ac_b_ex.fe_len
it is still greater than EXT_MAX_BLOCKS, which causes ex.fe_logical to
overflow to a very small value, which ultimately triggers a BUG_ON in
ext4_mb_new_inode_pa() because pa->pa_free < len.
The last logical block of an actual write request does not exceed
EXT_MAX_BLOCKS, so in ext4_mb_normalize_request() also avoids normalizing
the last logical block to exceed EXT_MAX_BLOCKS to avoid the above issue.
The test case in [Link] can reproduce the above issue with 64k block size.
Link: https://patchwork.kernel.org/project/fstests/list/?series=804003
Cc: <stable@kernel.org> # 6.4
Fixes:
|
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