diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/remove.c | 49 |
1 files changed, 46 insertions, 3 deletions
diff --git a/src/remove.c b/src/remove.c index ea5284341..6c1eaea5c 100644 --- a/src/remove.c +++ b/src/remove.c @@ -1277,6 +1277,45 @@ dirent_count (struct stat const *st) } #endif /* HAVE_STRUCT_DIRENT_D_TYPE */ +#if defined HAVE_SYS_VFS_H && HAVE_FSTATFS && HAVE_STRUCT_STATFS_F_TYPE +# include <sys/statfs.h> +# include "fs.h" +/* FIXME: what about when f_type is not an integral type? + deal with that if/when it's encountered. */ +static bool +fs_handles_readdir_ordered_dirents_efficiently (uintmax_t fs_type) +{ + switch (fs_type) + { + case S_MAGIC_TMPFS: + case S_MAGIC_NFS: + return true; + default: + return false; + } +} + +/* Return true if it is easy to determine the file system type of the + directory on which DIR_FD is open, and sorting dirents on inode numbers + is known to improve traversal performance with that type of file system. */ +static bool +dirent_inode_sort_may_be_useful (int dir_fd) +{ + /* Skip the sort only if we can determine efficiently + that skipping it is the right thing to do. + The cost of performing an unnecessary sort is negligible, + while the cost of *not* performing it can be O(N^2) with + a very large constant. */ + struct statfs fs_buf; + bool skip = (fstatfs (dir_fd, &fs_buf) == 0 + && fs_handles_readdir_ordered_dirents_efficiently + (fs_buf.f_type)); + return !skip; +} +#else +static bool dirent_inode_sort_may_be_useful (int dir_fd) { return true; } +#endif + /* When a directory contains very many entries, operating on N entries in readdir order can be very seek-intensive (be it to unlink or even to merely stat each entry), to the point that it results in O(N^2) work. @@ -1303,6 +1342,7 @@ preprocess_dir (DIR **dirp, struct rm_options const *x) Skip this optimization if... */ + int dir_fd = dirfd (*dirp); if (/* - there is a chance of interactivity */ x->interactive != RMI_NEVER @@ -1316,13 +1356,16 @@ preprocess_dir (DIR **dirp, struct rm_options const *x) || ! cannot_unlink_dir () /* - we can't fstat the file descriptor */ - || fstat (dirfd (*dirp), &st) != 0 + || fstat (dir_fd, &st) != 0 /* - the directory is smaller than some threshold. Estimate the number of inodes with a heuristic. There's no significant benefit to sorting if there are too few inodes. */ - || dirent_count (&st) < INODE_SORT_DIR_ENTRIES_THRESHOLD) + || dirent_count (&st) < INODE_SORT_DIR_ENTRIES_THRESHOLD + + /* Sort only if it might help. */ + || ! dirent_inode_sort_may_be_useful (dir_fd)) return; /* FIXME: maybe test file system type, too; skip if it's tmpfs: see fts.c */ @@ -1378,7 +1421,7 @@ preprocess_dir (DIR **dirp, struct rm_options const *x) for (size_t i = 0; i < n; i++) { /* ignore failure */ - (void) unlinkat (dirfd (*dirp), vv[i]->name, 0); + (void) unlinkat (dir_fd, vv[i]->name, 0); } cleanup: |