109 lines
3.2 KiB
Diff
109 lines
3.2 KiB
Diff
From 62cd6c9d2dd62dd24cc04b16437bfb816a6f4357 Mon Sep 17 00:00:00 2001
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From: Laszlo Ersek <lersek@redhat.com>
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Date: Mon, 2 May 2022 10:56:01 +0200
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Subject: [PATCH] guestfs_readdir(): minimize the number of send_file_write()
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calls
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In guestfs_readdir(), the daemon currently sends each XDR-encoded
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"guestfs_int_dirent" to the library with a separate send_file_write()
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call.
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Determine the largest encoded size (from the longest filename that a
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"guestfs_int_dirent" could carry, from readdir()'s "struct dirent"), and
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batch up the XDR encodings until the next encoding might not fit in
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GUESTFS_MAX_CHUNK_SIZE. Call send_file_write() only then.
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1674392
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Signed-off-by: Laszlo Ersek <lersek@redhat.com>
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Message-Id: <20220502085601.15012-3-lersek@redhat.com>
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Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
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(cherry picked from commit 4864d21cb8eb991f0fc98d03a068173837cba50e)
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---
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daemon/readdir.c | 38 ++++++++++++++++++++++++++++++++------
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1 file changed, 32 insertions(+), 6 deletions(-)
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diff --git a/daemon/readdir.c b/daemon/readdir.c
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index 9ab0b0aec..3084ba939 100644
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--- a/daemon/readdir.c
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+++ b/daemon/readdir.c
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@@ -35,6 +35,9 @@ do_internal_readdir (const char *dir)
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DIR *dirstream;
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void *xdr_buf;
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XDR xdr;
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+ struct dirent fill;
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+ guestfs_int_dirent v;
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+ unsigned max_encoded;
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/* Prepare to fail. */
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ret = -1;
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@@ -55,6 +58,20 @@ do_internal_readdir (const char *dir)
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}
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xdrmem_create (&xdr, xdr_buf, GUESTFS_MAX_CHUNK_SIZE, XDR_ENCODE);
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+ /* Calculate the max number of bytes a "guestfs_int_dirent" can be encoded to.
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+ */
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+ memset (fill.d_name, 'a', sizeof fill.d_name - 1);
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+ fill.d_name[sizeof fill.d_name - 1] = '\0';
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+ v.ino = INT64_MAX;
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+ v.ftyp = '?';
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+ v.name = fill.d_name;
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+ if (!xdr_guestfs_int_dirent (&xdr, &v)) {
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+ fprintf (stderr, "xdr_guestfs_int_dirent failed\n");
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+ goto release_xdr;
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+ }
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+ max_encoded = xdr_getpos (&xdr);
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+ xdr_setpos (&xdr, 0);
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+
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/* Send an "OK" reply, before starting the file transfer. */
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reply (NULL, NULL);
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@@ -63,7 +80,6 @@ do_internal_readdir (const char *dir)
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*/
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for (;;) {
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struct dirent *d;
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- guestfs_int_dirent v;
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errno = 0;
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d = readdir (dirstream);
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@@ -94,22 +110,32 @@ do_internal_readdir (const char *dir)
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v.ftyp = 'u';
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#endif
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+ /* Flush "xdr_buf" if we may not have enough room for encoding "v". */
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+ if (GUESTFS_MAX_CHUNK_SIZE - xdr_getpos (&xdr) < max_encoded) {
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+ if (send_file_write (xdr_buf, xdr_getpos (&xdr)) != 0)
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+ break;
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+
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+ xdr_setpos (&xdr, 0);
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+ }
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+
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if (!xdr_guestfs_int_dirent (&xdr, &v)) {
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fprintf (stderr, "xdr_guestfs_int_dirent failed\n");
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break;
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}
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-
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- if (send_file_write (xdr_buf, xdr_getpos (&xdr)) != 0)
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- break;
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-
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- xdr_setpos (&xdr, 0);
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}
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+ /* Flush "xdr_buf" if the loop completed successfully and "xdr_buf" is not
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+ * empty. */
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+ if (ret == 0 && xdr_getpos (&xdr) > 0 &&
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+ send_file_write (xdr_buf, xdr_getpos (&xdr)) != 0)
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+ ret = -1;
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+
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/* Finish or cancel the transfer. Note that if (ret == -1) because the library
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* canceled, we still need to cancel back!
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*/
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send_file_end (ret == -1);
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+release_xdr:
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xdr_destroy (&xdr);
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free (xdr_buf);
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--
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2.31.1
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