xfs_io: fix fiemap loop continuation

When the fiemap command needs to retrieve more extents from the
kernel via a subsequent IO, it calculates the next logical block to
retrieve in file system block units. the fiemap needs the start
offset in bytes, not filesystem blocks.  Hence if the fiemap command
can loop forever retrieving the same blocks if the logical offset
offset of the next block in filesystem block units is smaller than
the number of bytes in a filessytem block. i.e. it will just loop
retreiving the first 32 extents from offset block zero.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/io/fiemap.c b/io/fiemap.c
index 99296ddbafeecbe3f12ee0f9c1cdf40c9ef553bc..e32a41668adc9ffda0b8fc604c44def9b5633ac7 100644 (file)
--- a/io/fiemap.c
+++ b/io/fiemap.c
@@ -75,12 +75,14 @@ print_verbose(
        __u64                   *last_logical)
 {
        __u64                   lstart;
+       __u64                   llast;
        __u64                   len;
        __u64                   block;
        char                    lbuf[48];
        char                    bbuf[48];
        char                    flgbuf[16];
 
+       llast = *last_logical / blocksize;
        lstart = extent->fe_logical / blocksize;
        len = extent->fe_length / blocksize;
        block = extent->fe_physical / blocksize;
@@ -88,11 +90,11 @@ print_verbose(
        memset(lbuf, 0, sizeof(lbuf));
        memset(bbuf, 0, sizeof(bbuf));
 
-       if (lstart != *last_logical) {
-               snprintf(lbuf, sizeof(lbuf), "[%llu..%llu]:", *last_logical,
+       if (lstart != llast) {
+               snprintf(lbuf, sizeof(lbuf), "[%llu..%llu]:", llast,
                         lstart - 1ULL);
                printf("%4d: %-*s %-*s %*llu\n", *cur_extent, foff_w, lbuf,
-                      boff_w, _("hole"), tot_w, lstart - *last_logical);
+                      boff_w, _("hole"), tot_w, lstart - llast);
                (*cur_extent)++;
                memset(lbuf, 0, sizeof(lbuf));
        }
@@ -121,19 +123,20 @@ print_plain(
        __u64                   *last_logical)
 {
        __u64                   lstart;
+       __u64                   llast;
        __u64                   block;
        __u64                   len;
 
+       llast = *last_logical / blocksize;
        lstart = extent->fe_logical / blocksize;
        len = extent->fe_length / blocksize;
        block = extent->fe_physical / blocksize;
 
-       if (lstart != *last_logical) {
+       if (lstart != llast) {
                printf("\t%d: [%llu..%llu]: hole", *cur_extent,
-                      *last_logical, lstart - 1ULL);
+                      llast, lstart - 1ULL);
                if (lflag)
-                       printf(_(" %llu blocks\n"),
-                              lstart - *last_logical);
+                       printf(_(" %llu blocks\n"), lstart - llast);
                else
                        printf("\n");
                (*cur_extent)++;
@@ -281,6 +284,7 @@ fiemap_f(
                                print_plain(extent, lflag, blocksize,
                                            max_extents, &cur_extent,
                                            &last_logical);
+
                        if (extent->fe_flags & FIEMAP_EXTENT_LAST) {
                                last = 1;
                                break;
@@ -303,22 +307,21 @@ fiemap_f(
                return 0;
        }
 
-       if (cur_extent && last_logical < (st.st_size / blocksize)) {
+       if (cur_extent && last_logical < st.st_size) {
                char    lbuf[32];
 
                snprintf(lbuf, sizeof(lbuf), "[%llu..%llu]:",
-                        last_logical, (st.st_size / blocksize) - 1);
+                        last_logical / blocksize, (st.st_size / blocksize) - 1);
                if (vflag) {
                        printf("%4d: %-*s %-*s %*llu\n", cur_extent,
                               foff_w, lbuf, boff_w, _("hole"), tot_w,
-                              (st.st_size / blocksize) - last_logical);
+                              (st.st_size - last_logical) / blocksize);
                } else {
                        printf("\t%d: %s %s", cur_extent, lbuf,
                               _("hole"));
                        if (lflag)
                                printf(_(" %llu blocks\n"),
-                                      (st.st_size / blocksize) -
-                                      last_logical);
+                                      (st.st_size - last_logical) / blocksize);
                        else
                                printf("\n");
                }