[PATCH v2 5/8] smb: client: apply rasize on remount

From: Rajasi Mandal <[email protected]>

rasize is accepted during remount parsing but sb->s_bdi->ra_pages is
only set in cifs_read_super() at mount time. A remount with a new
rasize value silently has no effect on the readahead window.

Update ra_pages in smb3_reconfigure() after the context has been
duplicated, using the same logic as cifs_read_super(): if rasize is
set, use it directly; otherwise fall back to 2 * rsize.

Not addressed here (pre-existing, independent of the rasize change):
a bare remount realigns a sub-PAGE_SIZE server-negotiated rsize/wsize
up to PAGE_SIZE via CIFS_ALIGN_*; and smb3_reconfigure() briefly NULLs
cifs_sb->ctx->source through STEAL_STRING() before restoring it, so a
concurrent DFS reconnect reading cifs_sb->ctx->source locklessly could
observe NULL.  Both predate this series; the latter shares the
unserialized cifs_sb->ctx root cause described in patch 1.  Left for
separate changes.

Signed-off-by: Rajasi Mandal <[email protected]>
Reviewed-by: Meetakshi Setiya <[email protected]>
---
 fs/smb/client/fs_context.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
index 4a319c113196..ee8e38c3b7f4 100644
--- a/fs/smb/client/fs_context.c
+++ b/fs/smb/client/fs_context.c
@@ -1368,7 +1368,7 @@ static int smb3_reconfigure(struct fs_context *fc)
 	struct dentry *root = fc->root;
 	struct cifs_sb_info *cifs_sb = CIFS_SB(root->d_sb);
 	struct cifs_ses *ses = cifs_sb_master_tcon(cifs_sb)->ses;
-	unsigned int rsize = ctx->rsize, wsize = ctx->wsize;
+	unsigned int rsize = ctx->rsize, wsize = ctx->wsize, rasize = ctx->rasize;
 	char *new_password = NULL, *new_password2 = NULL;
 	bool need_recon = false;
 	bool need_mchan_update;
@@ -1462,9 +1462,10 @@ static int smb3_reconfigure(struct fs_context *fc)
 		STEAL_STRING_SENSITIVE(cifs_sb, ctx, password2);
 	}
 
-	/* if rsize or wsize not passed in on remount, use previous values */
+	/* if rsize, wsize, or rasize not passed in on remount, use previous values */
 	ctx->rsize = rsize ? CIFS_ALIGN_RSIZE(fc, rsize) : cifs_sb->ctx->rsize;
 	ctx->wsize = wsize ? CIFS_ALIGN_WSIZE(fc, wsize) : cifs_sb->ctx->wsize;
+	ctx->rasize = rasize ? rasize : cifs_sb->ctx->rasize;
 
 	new_ctx = kzalloc_obj(*new_ctx);
 	if (!new_ctx) {
@@ -1553,6 +1554,12 @@ static int smb3_reconfigure(struct fs_context *fc)
 	smb3_cleanup_fs_context(old_ctx);
 	old_ctx = NULL;
 	smb3_update_mnt_flags(cifs_sb);
+
+	if (cifs_sb->ctx->rasize)
+		root->d_sb->s_bdi->ra_pages = cifs_sb->ctx->rasize / PAGE_SIZE;
+	else
+		root->d_sb->s_bdi->ra_pages = 2 * (cifs_sb->ctx->rsize / PAGE_SIZE);
+
 #ifdef CONFIG_CIFS_DFS_UPCALL
 	if (!rc)
 		rc = dfs_cache_remount_fs(cifs_sb);
-- 
2.43.0