Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753206Ab0FKFGv (ORCPT ); Fri, 11 Jun 2010 01:06:51 -0400 Received: from rcsinet10.oracle.com ([148.87.113.121]:21427 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752023Ab0FKFGu (ORCPT ); Fri, 11 Jun 2010 01:06:50 -0400 Message-ID: <4C11C41C.9070000@oracle.com> Date: Fri, 11 Jun 2010 13:05:32 +0800 From: Tao Ma User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.9) Gecko/20100317 Thunderbird/3.0.4 MIME-Version: 1.0 To: Eric Sandeen CC: linux-ext4@vger.kernel.org, Theodore Tso , linux-kernel@vger.kernel.org Subject: Re: fiemap is broken for sparse file in ext4? References: <4C119C2E.2090801@oracle.com> <4C11B6D8.8070909@redhat.com> In-Reply-To: <4C11B6D8.8070909@redhat.com> Content-Type: multipart/mixed; boundary="------------040202060109010804080907" X-Auth-Type: Internal IP X-Source-IP: rcsinet13.oracle.com [148.87.113.125] X-CT-RefId: str=0001.0A090209.4C11C45D.00C7:SCFMA4539811,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5088 Lines: 196 This is a multi-part message in MIME format. --------------040202060109010804080907 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Hi Eric, Thanks for the quick response. On 06/11/2010 12:08 PM, Eric Sandeen wrote: > Tao Ma wrote: >> Hi Ted and other ext4 gurus, >> I found fiemap may be broken for sparse files in ext4. Here is a >> simple example. >> >> dd if=/dev/zero of=testfile1 bs=1M count=1 >> using fiemap shows that it has a delalloc extent. >> Logical: 0 Ext length: 1048576 Physical: 0 flags: 7 >> >> flags 7 means FIEMAP_EXTENT_LAST, FIEMAP_EXTENT_UNKNOWN and >> FIEMAP_EXTENT_DELALLOC, >> >> while if we create a sparse file, fiemap will not show the delalloc extent. >> dd if=/dev/zero of=testfile1 bs=1M count=1 seek=1 >> using fiemap shows that it has no extent for the file. while we should >> have some output like: >> Logical: 1048576 Ext length: 1048576 Physical: 0 flags: 7 >> >> So we have different output with sparse and non-sparse file. Is it a bug >> for ext4? > > What are you using to call fiemap? Here it seems to be working: I just wrote a simple test program by calling ioctl. It is attached. btw, you need to call it immediately after dd so that we have a chance that ext4 don't have time to allocate extents. ;) > > # dd if=/dev/zero of=testfile1 bs=1M count=1 seek=1; > > # filefrag -v testfile1 > Filesystem type is: ef53 > Filesystem cylinder groups is approximately 119 > File size of testfile1 is 2097152 (512 blocks, blocksize 4096) > ext logical physical expected length flags > 0 256 151946 1 merged > 1 257 151951 151946 2 merged > 2 259 152434 151952 253 merged,eof > testfile1: 4 extents found I guess maybe filefrag use the diffrent ioctl flag, maybe FIEMAP_FLAG_SYNC to let ext4 sync first. Regards, Tao --------------040202060109010804080907 Content-Type: text/x-csrc; name="fiemap.c" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="fiemap.c" #include #include #include #include #include #include #include #include #include #include #include #include "fiemap.h" #define FS_IOC_FIEMAP _IOWR('f', 11, struct fiemap) static unsigned int num_extents = 1024; static unsigned int estimate_extents = 1; static unsigned long long map_start = 0ULL; static unsigned long long map_len = FIEMAP_MAX_OFFSET; static char *fname; static unsigned int blocksize = 4096; static void usage(void) { printf("Usage: fiemap filename\n"); exit(1); } static void print_extent(struct fiemap_extent *extent) { __u64 val; printf("Logical: ###[%8"PRIu64"]\t", extent->fe_logical); printf("Ext length: ###[%8"PRIu64"]\t", extent->fe_length); printf("Physical: ###[%8"PRIu64"]\t", extent->fe_physical); printf("flags: %u\t", extent->fe_flags); if (extent->fe_flags & FIEMAP_EXTENT_SHARED) printf("Yeah, found an shared extent\n"); if (extent->fe_flags & FIEMAP_EXTENT_UNWRITTEN) printf("Yeah, you are hole?\n"); printf("\n"); } static void show_results(struct fiemap *fiemap) { int i; printf("Extents returned: %u\n", fiemap->fm_mapped_extents); if (fiemap->fm_extent_count == 0 || fiemap->fm_mapped_extents == 0) return; for (i = 0; i < fiemap->fm_mapped_extents; i++) print_extent(&fiemap->fm_extents[i]); } static int figure_extents(int fd, unsigned int *num) { int ret; struct fiemap fiemap = { 0, }; fiemap.fm_start = map_start; fiemap.fm_length = map_len; fiemap.fm_flags = 0; ret = ioctl(fd, FS_IOC_FIEMAP, &fiemap); if (ret == -1) { fprintf(stderr, "fiemap get count error %d: \"%s\"\n", errno, strerror(errno)); return -1; } *num = fiemap.fm_mapped_extents; return 0; } int main(int argc, char **argv) { int ret, fd; struct fiemap *fiemap; fd = open(argv[1], O_RDONLY); if (fd == -1) { fprintf(stderr, "open error %d: \"%s\"\n", errno, strerror(errno)); return -1; } if (figure_extents(fd, &num_extents)) return -1; printf("Extents in file \"%s\": %u\n", argv[1], num_extents); fiemap = malloc(sizeof(fiemap) + num_extents * sizeof(struct fiemap_extent)); if (fiemap == NULL) { fprintf(stderr, "malloc error %d: \"%s\"\n", errno, strerror(errno)); return -1; } fiemap->fm_start = map_start; fiemap->fm_length = map_len; fiemap->fm_extent_count = num_extents; ret = ioctl(fd, FS_IOC_FIEMAP, fiemap); if (ret == -1) { if (errno == EBADR) { fprintf(stderr, "Kernel does not support the flags: 0x%x\n", fiemap->fm_flags); return -1; } fprintf(stderr, "fiemap error %d: \"%s\"\n", errno, strerror(errno)); return -1; } show_results(fiemap); close(fd); return 0; } --------------040202060109010804080907-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/