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Restore fd optimization with a few minor tweaks, to quote tegge:

Browse Source 
"fdinit() fails to initialize newfdp->fd_fd.fd_lastfile to -1.  This breaks
fdcopy() which will incorrectly set newfdp->fd_freefile to 1 if no files are
open and the last file descriptor marked as unused for fdp was 0.  This later
causes descriptor 0 to be unavailable in newfdp when the optimization is
enabled.

When the last file descriptor previously marked as used is nonzero and marked
as unused, fdunused() incorrectly sets fdp->fd_lastfile to fd - 1 due to
fd_last_used() returning (size - 1).  This hides the problem that breaks the
optimization."

This allows us to keep the optimization, while un-breaking it.

This is a RELENG_6 candidate.

PR:		kern/87208
MFC after:	1 week
Submitted by:	tegge
This commit is contained in:
Christian S.J. Peron 2006-03-20 00:13:47 +00:00
parent 700118c72f
commit 2ed4894a26
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=156900
1 changed files with 5 additions and 2 deletions
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7
sys/kern/kern_descrip.c
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@ -193,7 +193,7 @@ fd_last_used(struct filedesc *fdp, int low, int size)
for (minoff = NDSLOT(low); off >= minoff; --off)
if (map[off] != 0)
return (off * NDENTRIES + flsl(map[off]) - 1);
return (size - 1);
return (low - 1);
}
static int
@ -1257,6 +1257,9 @@ fdalloc(struct thread *td, int minfd, int *result)
FILEDESC_LOCK_ASSERT(fdp, MA_OWNED);
if (fdp->fd_freefile > minfd)
minfd = fdp->fd_freefile;
PROC_LOCK(p);
maxfd = min((int)lim_cur(p, RLIMIT_NOFILE), maxfilesperproc);
PROC_UNLOCK(p);
@ -1286,7 +1289,6 @@ fdalloc(struct thread *td, int minfd, int *result)
("free descriptor isn't"));
fdp->fd_ofileflags[fd] = 0; /* XXX needed? */
fdused(fdp, fd);
fdp->fd_freefile = fd_first_free(fdp, fd, fdp->fd_nfiles);
*result = fd;
return (0);
}
@ -1420,6 +1422,7 @@ fdinit(struct filedesc *fdp)
newfdp->fd_fd.fd_ofileflags = newfdp->fd_dfileflags;
newfdp->fd_fd.fd_nfiles = NDFILE;
newfdp->fd_fd.fd_map = newfdp->fd_dmap;
newfdp->fd_fd.fd_lastfile = -1;
return (&newfdp->fd_fd);
}