Hi, As I am looking more closely to the EXT4_IOC_MOVE_EXT ioctl, I found a problem. The iotcl exchanges the block layout of the orig file and donor file and then writes out orig file data to orig file's new blocks. After the ioctl, the donor file would have the blocks previously owned by the orig file. But it turns out inconsistent. A simple test case for revealing the bug: The program a.out is calling EXT4_IOC_MOVE_EXT against argv[1] (as orig file) and argv[2] (as donor file) and move_data.len = argv[1]'s block count. And I am running mainline kernel 2.6.32-rc3 and the ext4 partition is mounted in ordered mode with default settings, if you are interested. [bergwolf@move_extent]$sh test-5.sh make full-img ========create full.img======== dd if=/home/bergwolf/vm/OpenSolaris200805.iso of=full-1.img bs=1M count=30 30+0 records in 30+0 records out 31457280 bytes (31 MB) copied, 0.0847457 s, 371 MB/s dd if="/home/bergwolf/vm/WINXP_EN_PRO_SP3_MSDN/WinXp+Sp3 enu.iso" of=full-2.img bs=1M count=30 30+0 records in 30+0 records out 31457280 bytes (31 MB) copied, 0.0664263 s, 474 MB/s md5sum full-1.img full-2.img 4f47bee75290d094c94f8a7cb2075c69 full-1.img 9e35330146a610d0aa2fab1d16aa2b09 full-2.img ./a.out full-1.img full-2.img md5sum full-1.img full-2.img 4f47bee75290d094c94f8a7cb2075c69 full-1.img 9e35330146a610d0aa2fab1d16aa2b09 full-2.img <---- wrong content [bergwolf@move_extent]$cd [bergwolf@~]$sudo umount /other/ [bergwolf@~]$sudo mount /other/ [bergwolf@~]$cd - /other/test/move_extent [bergwolf@move_extent]$md5sum full-1.img full-2.img 4f47bee75290d094c94f8a7cb2075c69 full-1.img 4f47bee75290d094c94f8a7cb2075c69 full-2.img <---- right result I verified that the bug is because of the pagecache hit in the vfs_read(), via the following test case: [bergwolf@move_extent]$sudo sh test-4.sh make full-img ========create full.img======== dd if=/home/bergwolf/vm/OpenSolaris200805.iso of=full-1.img bs=1M count=30 30+0 records in 30+0 records out 31457280 bytes (31 MB) copied, 0.115624 s, 272 MB/s dd if="/home/bergwolf/vm/WINXP_EN_PRO_SP3_MSDN/WinXp+Sp3 enu.iso" of=full-2.img bs=1M count=30 30+0 records in 30+0 records out 31457280 bytes (31 MB) copied, 1.16482 s, 27.0 MB/s md5sum full-1.img full-2.img 4f47bee75290d094c94f8a7cb2075c69 full-1.img 9e35330146a610d0aa2fab1d16aa2b09 full-2.img sync echo 1 > /proc/sys/vm/drop_caches <------- this drops all pagecaches, FYI ./a.out full-1.img full-2.img md5sum full-1.img full-2.img 4f47bee75290d094c94f8a7cb2075c69 full-1.img 4f47bee75290d094c94f8a7cb2075c69 full-2.img IIUC, this is because pagecache not uptodate. FWIW, EXT4_IOC_MOVE_EXT calls ext4_ext_invalidate_cache() to prevent later access to donor file reading old data. But if the data is already in the pagecache (in which case, ext4_get_blocks() won't be called), vfs_read will still read the old data. But I don't know if there is a way to discard all pagecache for a specific inode. I tried to write something similar to ext4_da_block_invalidatepages() and ClearPageUptodate() on each page found in the mapping address, but it didn't work. So am I missing anything? And any hints how to force the following vfs_read() to read from disk? -- Best Regards, Peng Tao State Key Laboratory of Networking and Switching Technology Beijing Univ. of Posts and Telecoms.
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