Hello, We found that fsync and fdatasync syscalls sometimes don't sync data in an ext3 file system under the following conditions. 1. Kernel version is 2.6.6 or later (including 2.6.8.1 and 2.6.9-rc2). 2. Ext3's journalling mode is "data=journal". 3. Create a file (whose size is 1Mbytes) and execute umount/mount. 4. lseek to a random position within the file, write 8192 bytes data, and fsync or fdatasync. We presume the data was not written to the corresponding disk before returning from fsync or fdatasync syscall on the evidence as follows: 1. The response time of fsync() and fdatasync() was extremely short. We use the "diskio" tool, which is downloadable from OSDL page (http://developer.osdl.jp/projects/doubt/). The program showed that the response time was under 10 microseconds. This time cannot be achieved with data transfer on IDE and PCI bus! 2. The IDE writing routine ide_start_dma() was not called under DMA enabled. We inserted the print messages in the sys_write(), sys_fsync() and ide_start_dma() by the attached patch. Sometimes the "ide_start_dma: ..." message was not shown between "write: in ..." and "fsync: out ...". The problem was occurred since 2.6.5-bk1, which includes the patch "[PATCH] ext3 fsync() and fdatasync() speedup". We found that the problem was solved by deleting the part of the patch which modifies ext3_sync_file(). Maybe, i_state is not correctly set to I_DIRTY when the related page cache is dirty (is it true?) Attached file is tarball (tar + bzip2) which contains following files. The patches are for 2.6.8.1-kernel (applicable to 2.6.9-rc2), and the results were also produced with 2.6.8.1-kernel. - fsync.c.patch: patch for solving the problem - kernel.printk.patch: patch for showing the problem by printks - kernel.printk.log: printks from the kernel with the printk patch - results/*: output from "diskio" program (result for fsync, and O_SYNC for comparison) - kernel-2.6.8.1.config: .config file which we used to build kernel We use the following hardware to make the data: CPU: Intel Pentium 4 3GHz Hyper Threading, 2nd cache 512KB RAM: 1GBytes IDE controller: on-board ICH5 (ATA100) HDD: E-IDE (7200rpm, 8MB cache, ATA133) x 2 (one for system and the other for writing test data) (The problem was also reproduced with a SCSI system) Regards, Seiji -- Seiji Kihara Open Source Software Computing Project, NTT Cyber Space Laboratories, Yokosuka, JAPAN
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