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Btrfs: remove all subvol options before mounting top-level
Currently, setup_root_args() substitutes 's/subvol=[^,]*/subvolid=0/'. But, this means that if the user passes both a subvol and subvolid for some reason, we won't actually mount the top-level when we recursively mount. For example, consider: mkfs.btrfs -f /dev/sdb mount /dev/sdb /mnt btrfs subvol create /mnt/subvol1 # subvolid=257 btrfs subvol create /mnt/subvol2 # subvolid=258 umount /mnt mount -osubvol=/subvol1,subvolid=258 /dev/sdb /mnt In the final mount, subvol=/subvol1,subvolid=258 becomes subvolid=0,subvolid=258, and the last option takes precedence, so we mount subvol2 and try to look up subvol1 inside of it, which fails. So, instead, do a thorough scan through the argument list and remove any subvol= and subvolid= options, then append subvolid=0 to the end. This implicitly makes subvol= take precedence over subvolid=, but we're about to add a stricter check for that. This also makes setup_root_args() more generic, which we'll need soon. Reviewed-by: David Sterba <dsterba@suse.cz> Signed-off-by: Omar Sandoval <osandov@osandov.com> Signed-off-by: Chris Mason <clm@fb.com>
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1 changed files with 20 additions and 36 deletions
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@ -1133,52 +1133,36 @@ static inline int is_subvolume_inode(struct inode *inode)
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}
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/*
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* This will strip out the subvol=%s argument for an argument string and add
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* subvolid=0 to make sure we get the actual tree root for path walking to the
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* subvol we want.
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* This will add subvolid=0 to the argument string while removing any subvol=
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* and subvolid= arguments to make sure we get the top-level root for path
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* walking to the subvol we want.
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*/
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static char *setup_root_args(char *args)
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{
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unsigned len = strlen(args) + 2 + 1;
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char *src, *dst, *buf;
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char *buf, *dst, *sep;
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/*
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* We need the same args as before, but with this substitution:
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* s!subvol=[^,]+!subvolid=0!
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*
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* Since the replacement string is up to 2 bytes longer than the
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* original, allocate strlen(args) + 2 + 1 bytes.
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*/
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if (!args)
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return kstrdup("subvolid=0", GFP_NOFS);
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src = strstr(args, "subvol=");
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/* This shouldn't happen, but just in case.. */
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if (!src)
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return NULL;
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buf = dst = kmalloc(len, GFP_NOFS);
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/* The worst case is that we add ",subvolid=0" to the end. */
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buf = dst = kmalloc(strlen(args) + strlen(",subvolid=0") + 1, GFP_NOFS);
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if (!buf)
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return NULL;
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/*
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* If the subvol= arg is not at the start of the string,
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* copy whatever precedes it into buf.
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*/
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if (src != args) {
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*src++ = '\0';
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strcpy(buf, args);
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dst += strlen(args);
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while (1) {
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sep = strchrnul(args, ',');
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if (!strstarts(args, "subvol=") &&
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!strstarts(args, "subvolid=")) {
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memcpy(dst, args, sep - args);
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dst += sep - args;
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*dst++ = ',';
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}
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if (*sep)
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args = sep + 1;
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else
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break;
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}
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strcpy(dst, "subvolid=0");
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dst += strlen("subvolid=0");
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/*
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* If there is a "," after the original subvol=... string,
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* copy that suffix into our buffer. Otherwise, we're done.
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*/
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src = strchr(src, ',');
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if (src)
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strcpy(dst, src);
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return buf;
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}
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