The FTS_NOSTAT option is an optimisation that reduces the number
of stat(2) calls by keeping an eye of the number of links a directory has. It assumes that each subdirectory will have a hard link to its parent, to represent the ".." node, and stops calling stat(2) when all links are accounted for in a given directory. This assumption is really only valid for UNIX-like filesystems: A concrete example is NTFS. The NTFS "i-node" does contain a link count, but most/all directories have a link count between 0 and 2 inclusive. The end result is that find on an NTFS volume won't actually traverse the entire hierarchy of the directories passed to it. (Those with a link count of two are not traversed at all) The fix checks the "UFSness" of the filesystem before enabling the optimisation. Reviewed By: Tim Kientzle (kientzle@)
This commit is contained in:
Peter Edwards
parent
66a79ac95d
commit
99ca5b8804
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=129052
@ -37,6 +37,8 @@
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#ifndef _FTS_H_
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#define _FTS_H_
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struct _fts_private; /* implementation data */
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typedef struct {
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struct _ftsent *fts_cur; /* current node */
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struct _ftsent *fts_child; /* linked list of children */
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@ -63,6 +65,7 @@ typedef struct {
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#define FTS_STOP 0x200 /* (private) unrecoverable error */
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int fts_options; /* fts_open options, global flags */
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void *fts_clientptr; /* thunk for sort function */
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struct _fts_private *fts_priv; /* Implementation data */
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} FTS;
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typedef struct _ftsent {
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@ -43,6 +43,7 @@ __FBSDID("$FreeBSD$");
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#include <sys/types.h>
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#include <sys/param.h>
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#include <sys/stat.h>
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#include <sys/mount.h>
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#include <dirent.h>
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#include <errno.h>
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@ -63,6 +64,7 @@ static int fts_palloc(FTS *, size_t);
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static FTSENT *fts_sort(FTS *, FTSENT *, int);
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static u_short fts_stat(FTS *, FTSENT *, int);
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static int fts_safe_changedir(FTS *, FTSENT *, int, char *);
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static int fts_ufslinks(FTS *sp, const FTSENT *ent);
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#define ISDOT(a) (a[0] == '.' && (!a[1] || (a[1] == '.' && !a[2])))
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@ -77,12 +79,43 @@ static int fts_safe_changedir(FTS *, FTSENT *, int, char *);
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#define BNAMES 2 /* fts_children, names only */
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#define BREAD 3 /* fts_read */
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/*
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* Internal representation of FTS, including extra implementation details.
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* The FTS returned from fts_open is ftsp_fts from this structure, and it's
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* fts_priv in turn points back to this internal version. i.e. for a given
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* fts_private *priv: &priv->fts_fts == (FTS *)f == priv->fts_fts.fts_priv
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*/
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struct _fts_private {
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FTS ftsp_fts;
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struct statfs ftsp_statfs;
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dev_t ftsp_dev;
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int ftsp_linksreliable;
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};
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/*
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* The "FTS_NOSTAT" option can avoid a lot of calls to stat(2) if it knows
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* that a directory could not possibly have subdirectories. This is decided
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* by looking at the link count: A subdirectory would increment its parent's
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* link count by virtue of its own ".." entry.
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* This assumption only holds for UFS-like filesystems that implement links
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* and directories this way, so we must punt for others.
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*/
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static const char *ufslike_filesystems[] = {
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"ufs",
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"nfs",
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"nfs4",
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"ext2fs",
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0
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};
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FTS *
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fts_open(argv, options, compar)
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char * const *argv;
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int options;
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int (*compar)(const FTSENT * const *, const FTSENT * const *);
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{
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struct _fts_private *priv;
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FTS *sp;
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FTSENT *p, *root;
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int nitems;
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@ -96,11 +129,13 @@ fts_open(argv, options, compar)
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}
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/* Allocate/initialize the stream */
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if ((sp = malloc(sizeof(FTS))) == NULL)
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if ((priv = malloc(sizeof(struct _fts_private))) == NULL)
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return (NULL);
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memset(sp, 0, sizeof(FTS));
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memset(priv, 0, sizeof(struct _fts_private));
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sp = &priv->ftsp_fts;
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sp->fts_compar = compar;
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sp->fts_options = options;
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sp->fts_priv = priv;
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/* Shush, GCC. */
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tmp = NULL;
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@ -637,7 +672,10 @@ fts_build(sp, type)
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/* Be quiet about nostat, GCC. */
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nostat = 0;
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} else if (ISSET(FTS_NOSTAT) && ISSET(FTS_PHYSICAL)) {
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nlinks = cur->fts_nlink - (ISSET(FTS_SEEDOT) ? 0 : 2);
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if (fts_ufslinks(sp, cur))
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nlinks = cur->fts_nlink - (ISSET(FTS_SEEDOT) ? 0 : 2);
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else
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nlinks = -1;
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nostat = 1;
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} else {
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nlinks = -1;
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@ -1154,3 +1192,37 @@ fts_safe_changedir(sp, p, fd, path)
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errno = oerrno;
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return (ret);
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}
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/*
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* Check if the filesystem for "ent" has UFS-style links.
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*/
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static int
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fts_ufslinks(FTS *sp, const FTSENT *ent)
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{
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struct _fts_private *priv;
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const char **cpp;
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priv = sp->fts_priv;
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/*
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* If this node's device is different from the previous, grab
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* the filesystem information, and decide on the reliability
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* of the link information from this filesystem for stat(2)
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* avoidance.
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*/
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if (priv->ftsp_dev != ent->fts_dev) {
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if (statfs(ent->fts_path, &priv->ftsp_statfs) != -1) {
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priv->ftsp_dev = ent->fts_dev;
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priv->ftsp_linksreliable = 0;
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for (cpp = ufslike_filesystems; *cpp; cpp++) {
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if (strcmp(priv->ftsp_statfs.f_fstypename,
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*cpp) == 0) {
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priv->ftsp_linksreliable = 1;
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break;
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}
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}
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} else {
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priv->ftsp_linksreliable = 0;
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}
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}
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return priv->ftsp_linksreliable;
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}
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@ -37,6 +37,8 @@
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#ifndef _FTS_H_
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#define _FTS_H_
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struct _fts_private; /* implementation data */
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typedef struct {
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struct _ftsent *fts_cur; /* current node */
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struct _ftsent *fts_child; /* linked list of children */
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@ -63,6 +65,7 @@ typedef struct {
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#define FTS_STOP 0x200 /* (private) unrecoverable error */
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int fts_options; /* fts_open options, global flags */
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void *fts_clientptr; /* thunk for sort function */
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struct _fts_private *fts_priv; /* Implementation data */
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} FTS;
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typedef struct _ftsent {
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@ -43,6 +43,7 @@ __FBSDID("$FreeBSD$");
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#include <sys/types.h>
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#include <sys/param.h>
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#include <sys/stat.h>
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#include <sys/mount.h>
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#include <dirent.h>
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#include <errno.h>
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@ -63,6 +64,7 @@ static int fts_palloc(FTS *, size_t);
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static FTSENT *fts_sort(FTS *, FTSENT *, int);
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static u_short fts_stat(FTS *, FTSENT *, int);
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static int fts_safe_changedir(FTS *, FTSENT *, int, char *);
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static int fts_ufslinks(FTS *sp, const FTSENT *ent);
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#define ISDOT(a) (a[0] == '.' && (!a[1] || (a[1] == '.' && !a[2])))
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@ -77,12 +79,43 @@ static int fts_safe_changedir(FTS *, FTSENT *, int, char *);
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#define BNAMES 2 /* fts_children, names only */
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#define BREAD 3 /* fts_read */
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/*
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* Internal representation of FTS, including extra implementation details.
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* The FTS returned from fts_open is ftsp_fts from this structure, and it's
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* fts_priv in turn points back to this internal version. i.e. for a given
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* fts_private *priv: &priv->fts_fts == (FTS *)f == priv->fts_fts.fts_priv
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*/
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struct _fts_private {
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FTS ftsp_fts;
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struct statfs ftsp_statfs;
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dev_t ftsp_dev;
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int ftsp_linksreliable;
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};
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/*
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* The "FTS_NOSTAT" option can avoid a lot of calls to stat(2) if it knows
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* that a directory could not possibly have subdirectories. This is decided
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* by looking at the link count: A subdirectory would increment its parent's
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* link count by virtue of its own ".." entry.
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* This assumption only holds for UFS-like filesystems that implement links
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* and directories this way, so we must punt for others.
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*/
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static const char *ufslike_filesystems[] = {
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"ufs",
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"nfs",
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"nfs4",
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"ext2fs",
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0
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};
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FTS *
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fts_open(argv, options, compar)
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char * const *argv;
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int options;
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int (*compar)(const FTSENT * const *, const FTSENT * const *);
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{
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struct _fts_private *priv;
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FTS *sp;
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FTSENT *p, *root;
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int nitems;
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@ -96,11 +129,13 @@ fts_open(argv, options, compar)
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}
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/* Allocate/initialize the stream */
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if ((sp = malloc(sizeof(FTS))) == NULL)
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if ((priv = malloc(sizeof(struct _fts_private))) == NULL)
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return (NULL);
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memset(sp, 0, sizeof(FTS));
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memset(priv, 0, sizeof(struct _fts_private));
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sp = &priv->ftsp_fts;
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sp->fts_compar = compar;
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sp->fts_options = options;
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sp->fts_priv = priv;
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/* Shush, GCC. */
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tmp = NULL;
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@ -637,7 +672,10 @@ fts_build(sp, type)
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/* Be quiet about nostat, GCC. */
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nostat = 0;
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} else if (ISSET(FTS_NOSTAT) && ISSET(FTS_PHYSICAL)) {
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nlinks = cur->fts_nlink - (ISSET(FTS_SEEDOT) ? 0 : 2);
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if (fts_ufslinks(sp, cur))
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nlinks = cur->fts_nlink - (ISSET(FTS_SEEDOT) ? 0 : 2);
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else
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nlinks = -1;
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nostat = 1;
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} else {
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nlinks = -1;
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@ -1154,3 +1192,37 @@ fts_safe_changedir(sp, p, fd, path)
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errno = oerrno;
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return (ret);
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}
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/*
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* Check if the filesystem for "ent" has UFS-style links.
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*/
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static int
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fts_ufslinks(FTS *sp, const FTSENT *ent)
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{
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struct _fts_private *priv;
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const char **cpp;
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priv = sp->fts_priv;
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/*
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* If this node's device is different from the previous, grab
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* the filesystem information, and decide on the reliability
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* of the link information from this filesystem for stat(2)
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* avoidance.
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*/
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if (priv->ftsp_dev != ent->fts_dev) {
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if (statfs(ent->fts_path, &priv->ftsp_statfs) != -1) {
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priv->ftsp_dev = ent->fts_dev;
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priv->ftsp_linksreliable = 0;
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for (cpp = ufslike_filesystems; *cpp; cpp++) {
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if (strcmp(priv->ftsp_statfs.f_fstypename,
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*cpp) == 0) {
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priv->ftsp_linksreliable = 1;
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break;
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}
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}
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} else {
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priv->ftsp_linksreliable = 0;
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}
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}
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return priv->ftsp_linksreliable;
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}
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