filefrag: fix block size value

ioctl(FIGETBSZ) was used to get block size earlier but 2508eaa7
(filefrag: improvements to filefrag FIEMAP handling) moved to fstatfs
f_bsize which doesn't work well for many files systems.

Block size returned using fstatfs isn't block size but "optimal
transfer block size" as per man page.  Even stat st_blksize is
"preferred I/O block size" and in may file systems it may even vary
from file to file (POSIX).  This patch changes filefrag to use
FIGETBSZ preferentially over f_bsize.

[ Modified by tytso to add the fallback to f_bsize if FIGETBSZ fails
  for some reason ]

Signed-off-by: Rakesh Pandit <rakesh@tuxera.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/misc/filefrag.c b/misc/filefrag.c
index bb060b6..2ce1b9b 100644 (file)
--- a/misc/filefrag.c
+++ b/misc/filefrag.c
@@ -351,6 +351,7 @@ static int filefrag_fibmap(int fd, int blk_shift, int *num_extents,
 static int frag_report(const char *filename)
 {
        static struct statfs fsinfo;
+       static unsigned int blksize;
        ext2fs_struct_stat st;
        int             blk_shift;
        long            fd;
@@ -381,22 +382,22 @@ static int frag_report(const char *filename)
 #endif
                rc = -errno;
                perror("stat");
-               close(fd);
-               return rc;
+               goto out_close;
        }
 
        if (last_device != st.st_dev) {
                if (fstatfs(fd, &fsinfo) < 0) {
                        rc = -errno;
                        perror("fstatfs");
-                       close(fd);
-                       return rc;
+                       goto out_close;
                }
+               if (ioctl(fd, FIGETBSZ, &blksize) < 0)
+                       blksize = fsinfo.f_bsize;
                if (verbose)
                        printf("Filesystem type is: %lx\n",
                               (unsigned long)fsinfo.f_type);
        }
-       st.st_blksize = fsinfo.f_bsize;
+       st.st_blksize = blksize;
        if (ioctl(fd, EXT3_IOC_GETFLAGS, &flags) < 0)
                flags = 0;
        if (!(flags & EXT4_EXTENTS_FL) &&
@@ -405,13 +406,13 @@ static int frag_report(const char *filename)
                is_ext2++;
 
        if (is_ext2) {
-               long cylgroups = div_ceil(fsinfo.f_blocks, fsinfo.f_bsize * 8);
+               long cylgroups = div_ceil(fsinfo.f_blocks, blksize * 8);
 
                if (verbose && last_device != st.st_dev)
                        printf("Filesystem cylinder groups approximately %ld\n",
                               cylgroups);
 
-               data_blocks_per_cyl = fsinfo.f_bsize * 8 -
+               data_blocks_per_cyl = blksize * 8 -
                                        (fsinfo.f_files / 8 / cylgroups) - 3;
        }
        last_device = st.st_dev;
@@ -420,11 +421,11 @@ static int frag_report(const char *filename)
        if (width > physical_width)
                physical_width = width;
 
-       numblocks = (st.st_size + fsinfo.f_bsize - 1) / fsinfo.f_bsize;
+       numblocks = (st.st_size + blksize - 1) / blksize;
        if (blocksize != 0)
                blk_shift = int_log2(blocksize);
        else
-               blk_shift = int_log2(fsinfo.f_bsize);
+               blk_shift = int_log2(blksize);
 
        width = int_log10(numblocks);
        if (width > logical_width)
@@ -432,7 +433,7 @@ static int frag_report(const char *filename)
        if (verbose)
                printf("File size of %s is %llu (%llu block%s of %d bytes)\n",
                       filename, (unsigned long long)st.st_size,
-                      numblocks * fsinfo.f_bsize >> blk_shift,
+                      numblocks * blksize >> blk_shift,
                       numblocks == 1 ? "" : "s", 1 << blk_shift);
 
        if (!force_bmap) {