hexdump: add fetch_more_extents to retrieve all file extents

Add fetch_more_extents() so FIEMAP can fetch extents in batches beyond
the initial fixed batch, instead of being limited to FIEMAP_EXTENTS_BATCH
extents only.

diff --git a/text-utils/hexdump-display.c b/text-utils/hexdump-display.c
index 13235cd8ec74fe549bb2df2a058b4d81cf13da97..f0db9c12a08be24ceb0569016f8fe1885ff37e6c 100644 (file)
--- a/text-utils/hexdump-display.c
+++ b/text-utils/hexdump-display.c
@@ -107,33 +107,38 @@ static void init_fiemap(struct hexdump *hex, int fd)
                return;
        }
 
-       /* Check if we got all extents or need more */
-       if (fm->fm_mapped_extents == FIEMAP_EXTENTS_BATCH &&
-           !(fm->fm_extents[fm->fm_mapped_extents - 1].fe_flags & FIEMAP_EXTENT_LAST)) {
-               unsigned int count = FIEMAP_EXTENTS_BATCH * 16;
-               free(fm);
-               fm_size = sizeof(struct fiemap) + sizeof(struct fiemap_extent) * count;
-               fm = xcalloc(1, fm_size);
-               fm->fm_start = 0;
-               fm->fm_length = st.st_size;
-               fm->fm_flags = 0;
-               fm->fm_extent_count = count;
-
-               if (ioctl(fd, FS_IOC_FIEMAP, fm) < 0) {
-                       free(fm);
-                       return;
-               }
-       }
-
        hex->fiemap = fm;
 }
 
+/*
+ * Fetch next batch of extents.  Returns 1 on success, 0 on failure.
+ */
+static int fetch_more_extents(struct hexdump *hex, int fd)
+{
+       struct fiemap *fm = hex->fiemap;
+       struct fiemap_extent *last_ext;
+
+       if (!fm || fm->fm_mapped_extents == 0)
+               return 0;
+
+       last_ext = &fm->fm_extents[fm->fm_mapped_extents - 1];
+       fm->fm_start = last_ext->fe_logical + last_ext->fe_length;
+       fm->fm_length = ~0ULL;
+       fm->fm_extent_count = FIEMAP_EXTENTS_BATCH;
+
+       if (ioctl(fd, FS_IOC_FIEMAP, fm) < 0)
+               return 0;
+
+       hex->current_extent = 0;
+       return 1;
+}
+
 /*
  * Check if position is in a hole.
  *
  * Returns: 1 if in hole, 0 if in data.
  */
-static int check_hole(struct hexdump *hex, off_t pos)
+static int check_hole(struct hexdump *hex, off_t pos, int fd)
 {
        struct fiemap *fm = hex->fiemap;
        unsigned int i;
@@ -152,38 +157,50 @@ static int check_hole(struct hexdump *hex, off_t pos)
                return 1;
        }
 
-       /* Start search from current_extent for efficiency */
-       for (i = hex->current_extent; i < fm->fm_mapped_extents; i++) {
-               struct fiemap_extent *ext = &fm->fm_extents[i];
-               off_t ext_end = ext->fe_logical + ext->fe_length;
+       while (TRUE) {
+               /* Start search from current_extent for efficiency */
+               for (i = hex->current_extent; i < fm->fm_mapped_extents; i++) {
+                       struct fiemap_extent *ext = &fm->fm_extents[i];
+                       off_t ext_end = ext->fe_logical + ext->fe_length;
+
+                       if (pos < (off_t)ext->fe_logical) {
+                               /* pos is before this extent - it's in a hole */
+                               hex->current_extent = i;
+                               hex->in_sparse_hole = 1;
+                               hex->region_end = ext->fe_logical;
+                               return 1;
+                       }
+                       if (pos < ext_end) {
+                               /* pos is within this extent - it's in data */
+                               hex->current_extent = i;
+                               hex->in_sparse_hole = 0;
+                               hex->region_end = ext_end;
+                               return 0;
+                       }
+               }
 
-               if (pos < (off_t)ext->fe_logical) {
-                       /* pos is before this extent - it's in a hole */
-                       hex->current_extent = i;
+               /* check if it is the last one */
+               last_ext = &fm->fm_extents[fm->fm_mapped_extents - 1];
+               if (last_ext->fe_flags & FIEMAP_EXTENT_LAST) {
                        hex->in_sparse_hole = 1;
-                       hex->region_end = ext->fe_logical;
+                       hex->region_end = hex->file_size;
                        return 1;
                }
-               if (pos < ext_end) {
-                       /* pos is within this extent - it's in data */
-                       hex->current_extent = i;
+
+               /* fetch next batch of extents */
+               if (!fetch_more_extents(hex, fd)) {
                        hex->in_sparse_hole = 0;
-                       hex->region_end = ext_end;
+                       hex->region_end = hex->file_size;
                        return 0;
                }
-       }
 
-       last_ext = &fm->fm_extents[fm->fm_mapped_extents - 1];
-       if (last_ext->fe_flags & FIEMAP_EXTENT_LAST) {
-               hex->in_sparse_hole = 1;
-               hex->region_end = hex->file_size;
-               return 1;
+               fm = hex->fiemap;
+               if (fm->fm_mapped_extents == 0) {
+                       hex->in_sparse_hole = 1;
+                       hex->region_end = hex->file_size;
+                       return 1;
+               }
        }
-
-       /* Incomplete extent map - disable optimization for safety */
-       hex->in_sparse_hole = 0;
-       hex->region_end = hex->file_size;
-       return 0;
 }
 #endif /* __linux__ */
 
@@ -521,7 +538,7 @@ get(struct hexdump *hex)
                        off_t curpos = address + nread;
 
                        if (curpos >= hex->region_end)
-                               check_hole(hex, curpos);
+                               check_hole(hex, curpos, fileno(stdin));
 
                        if (hex->in_sparse_hole && vflag == DUP) {
                                int savp_is_zero = 1;