From: Jensen Date: Thu, 3 Apr 2014 21:47:01 +0000 (-0700) Subject: ocfs2: llseek requires ocfs2 inode lock for the file in SEEK_END X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=c8d888d9f1469806c339218fc342817eb3b628a8;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git ocfs2: llseek requires ocfs2 inode lock for the file in SEEK_END llseek requires ocfs2 inode lock for updating the file size in SEEK_END. because the file size maybe update on another node. This bug can be reproduce the following scenario: at first, we dd a test fileA, the file size is 10k. on NodeA: --------- 1) open the test fileA, lseek the end of file. and print the position. 2) close the test fileA on NodeB: 1) open the test fileA, append the 5k data to test FileA. 2) lseek the end of file. and print the position. 3) close file. At first we run the test program1 on NodeA , the result is 10k. And then run the test program2 on NodeB, the result is 15k. At last, we run the test program1 on NodeA again, the result is 10k. After applying this patch the three step result is 15k. test result: 1000000 times lseek call; index lseek with inode lock (unit:us) lseek without inode lock (unit:us) 1 1168162 555383 2 1168011 549504 3 1170538 549396 4 1170375 551685 5 1170444 556719 6 1174364 555307 7 1163294 551552 8 1170080 549350 9 1162464 553700 10 1165441 552594 avg 1168317 552519 avg with lock - avg without lock = 615798 (avg with lock - avg without lock)/1000000=0.615798 us Signed-off-by: Jensen Cc: Jie Liu Acked-by: Joel Becker Cc: Mark Fasheh Cc: Sunil Mushran Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c index bd94d26b0b21..0f14f906dc65 100644 --- a/fs/ocfs2/file.c +++ b/fs/ocfs2/file.c @@ -2630,7 +2630,16 @@ static loff_t ocfs2_file_llseek(struct file *file, loff_t offset, int whence) case SEEK_SET: break; case SEEK_END: - offset += inode->i_size; + /* SEEK_END requires the OCFS2 inode lock for the file + * because it references the file's size. + */ + ret = ocfs2_inode_lock(inode, NULL, 0); + if (ret < 0) { + mlog_errno(ret); + goto out; + } + offset += i_size_read(inode); + ocfs2_inode_unlock(inode, 0); break; case SEEK_CUR: if (offset == 0) {