linux/mm/filemap.c

2314 lines
58 KiB

[PATCH] mm: split page table lock Christoph Lameter demonstrated very poor scalability on the SGI 512-way, with a many-threaded application which concurrently initializes different parts of a large anonymous area. This patch corrects that, by using a separate spinlock per page table page, to guard the page table entries in that page, instead of using the mm's single page_table_lock. (But even then, page_table_lock is still used to guard page table allocation, and anon_vma allocation.) In this implementation, the spinlock is tucked inside the struct page of the page table page: with a BUILD_BUG_ON in case it overflows - which it would in the case of 32-bit PA-RISC with spinlock debugging enabled. Splitting the lock is not quite for free: another cacheline access. Ideally, I suppose we would use split ptlock only for multi-threaded processes on multi-cpu machines; but deciding that dynamically would have its own costs. So for now enable it by config, at some number of cpus - since the Kconfig language doesn't support inequalities, let preprocessor compare that with NR_CPUS. But I don't think it's worth being user-configurable: for good testing of both split and unsplit configs, split now at 4 cpus, and perhaps change that to 8 later. There is a benefit even for singly threaded processes: kswapd can be attacking one part of the mm while another part is busy faulting. Signed-off-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-29 18:16:40 -07:00
[PATCH] fix for __generic_file_aio_read() to return 0 on EOF I came across the following problem while running ltp-aiodio testcases from ltp-full-20050405 on linux-2.6.12-rc3-mm3. I tried running the tests with EXT3 as well as JFS filesystems. One or two fsx-linux testcases were hung after some time. These testcases were hanging at wait_for_all_aios(). Debugging shows that there were some iocbs which were not getting completed eventhough the last retry for those returned -EIOCBQUEUED. Also all such pending iocbs represented READ operation. Further debugging revealed that all such iocbs hit EOF in the DIO layer. To be more precise, the "pos" from which they were trying to read was greater than the "size" of the file. So the generic_file_direct_IO returned 0. This happens rarely as there is already a check in __generic_file_aio_read(), for whether "pos" < "size" before calling direct IO routine. >size = i_size_read(inode); >if (pos < size) { > retval = generic_file_direct_IO(READ, iocb, > iov, pos, nr_segs); But for READ, we are taking the inode->i_sem only in the DIO layer. So it is possible that some other process can change the size of the file before we take the i_sem. In such a case ( when "pos" > "size"), the __generic_file_aio_read() would return -EIOCBQUEUED even though there were no I/O requests submitted by the DIO layer. This would cause the AIO layer to expect aio_complete() for THE iocb, which doesnot happen. And thus the test hangs forever, waiting for an I/O completion, where there are no requests submitted at all. The following patch makes __generic_file_aio_read() return 0 (instead of returning -EIOCBQUEUED), on getting 0 from generic_file_direct_IO(), so that the AIO layer does the aio_complete(). Testing: I have tested the patch on a SMP machine(with 2 Pentium 4 (HT)) running linux-2.6.12-rc3-mm3. I ran the ltp-aiodio testcases and none of the fsx-linux tests hung. Also the aio-stress tests ran without any problem. Signed-off-by: Suzuki K P <suzuki@in.ibm.com> Signed-off-by: Suparna Bhattacharya <suparna@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-05-21 16:33:36 -07:00
[PATCH] fs: error case fix in __generic_file_aio_read When __generic_file_aio_read() hits an error during reading, it reports the error iff nothing has successfully been read yet. This is condition - when an error occurs, if nothing has been read/written, report the error code; otherwise, report the amount of bytes successfully transferred upto that point. This corner case can be exposed by performing readv(2) with the following iov. iov[0] = len0 @ ptr0 iov[1] = len1 @ NULL (or any other invalid pointer) iov[2] = len2 @ ptr2 When file size is enough, performing above readv(2) results in len0 bytes from file_pos @ ptr0 len2 bytes from file_pos + len0 @ ptr2 And the return value is len0 + len2. Test program is attached to this mail. This patch makes __generic_file_aio_read()'s error handling identical to other functions. #include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <unistd.h> #include <sys/uio.h> #include <errno.h> #include <string.h> int main(int argc, char **argv) { const char *path; struct stat stbuf; size_t len0, len1; void *buf0, *buf1; struct iovec iov[3]; int fd, i; ssize_t ret; if (argc < 2) { fprintf(stderr, "Usage: testreadv path (better be a " "small text file)\n"); return 1; } path = argv[1]; if (stat(path, &stbuf) < 0) { perror("stat"); return 1; } len0 = stbuf.st_size / 2; len1 = stbuf.st_size - len0; if (!len0 || !len1) { fprintf(stderr, "Dude, file is too small\n"); return 1; } if ((fd = open(path, O_RDONLY)) < 0) { perror("open"); return 1; } if (!(buf0 = malloc(len0)) || !(buf1 = malloc(len1))) { perror("malloc"); return 1; } memset(buf0, 0, len0); memset(buf1, 0, len1); iov[0].iov_base = buf0; iov[0].iov_len = len0; iov[1].iov_base = NULL; iov[1].iov_len = len1; iov[2].iov_base = buf1; iov[2].iov_len = len1; printf("vector "); for (i = 0; i < 3; i++) printf("%p:%zu ", iov[i].iov_base, iov[i].iov_len); printf("\n"); ret = readv(fd, iov, 3); if (ret < 0) perror("readv"); printf("readv returned %zd\nbuf0 = [%s]\nbuf1 = [%s]\n", ret, (char *)buf0, (char *)buf1); return 0; } Signed-off-by: Tejun Heo <htejun@gmail.com> Cc: Benjamin LaHaise <bcrl@kvack.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-30 15:02:40 -08:00