- 14 Mar, 2020 31 commits
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Al Viro authored
eventually we'll want to do that check *before* mangling nd->path.dentry... Signed-off-by:Al Viro <viro@zeniv.linux.org.uk>
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Al Viro authored
Signed-off-by: -
Al Viro authored
... getting may_create_in_sticky() checks in FMODE_OPENED case as well. Signed-off-by: -
Al Viro authored
Don't mess with got_write there - it is guaranteed to be false on entry and it will be set true if and only if we decide to go for truncation and manage to get write access for that. Don't carry acc_mode through the entire thing - it's only used in that part. And don't bother with gotos in there - compiler is quite capable of optimizing that. Signed-off-by: -
Al Viro authored
Signed-off-by: -
Al Viro authored
it's easier to drop it right after lookup_open() and regain if needed (i.e. if we will need to truncate). On the non-FMODE_OPENED path we do that anyway. In case of FMODE_CREATED we won't be needing it. And it's easier to prove correctness that way, especially since the initial failure to get write access is not always fatal; proving that we'll never end up truncating in that case is rather convoluted. Signed-off-by: -
Al Viro authored
have FMODE_OPENED case rejoin the main path at earlier point Signed-off-by: -
Al Viro authored
there we'll be able to merge it with its counterparts in other cases, and there's no reason to do it before the parent has been unlocked Signed-off-by: -
Al Viro authored
->atomic_open() might have used a different alias than the one we'd passed to it; in "not opened" case we take care of that, in "opened" one we don't. Currently we don't care downstream of "opened" case which alias to return; however, that will change shortly when we get to unifying may_open() calls. It's not hard to get right in all cases, anyway. Signed-off-by: -
Al Viro authored
common guts of follow_down() and follow_managed() taken to a new helper - traverse_mounts(). The remnants of follow_managed() are folded into its sole remaining caller (handle_mounts()). Calling conventions of handle_mounts() slightly sanitized - instead of the weird "1 for success, -E... for failure" that used to be imposed by the calling conventions of walk_component() et.al. we can use the normal "0 for success, -E... for failure". Signed-off-by: -
Al Viro authored
make the loop more similar to that in follow_managed(), with explicit tracking of flags, etc. Signed-off-by: -
Al Viro authored
set on entry, clear when we get to the last component. Signed-off-by: -
Al Viro authored
We use nd->stack to store two things: pinning down the symlinks we are resolving and resuming the name traversal when a nested symlink is finished. Currently, nd->depth is used to keep track of both. It's 0 when we call link_path_walk() for the first time (for the pathname itself) and 1 on all subsequent calls (for trailing symlinks, if any). That's fine, as far as pinning symlinks goes - when handling a trailing symlink, the string we are interpreting is the body of symlink pinned down in nd->stack[0]. It's rather inconvenient with respect to handling nested symlinks, though - when we run out of a string we are currently interpreting, we need to decide whether it's a nested symlink (in which case we need to pick the string saved back when we started to interpret that nested symlink and resume its traversal) or not (in which case we are done with link_path_walk()). Current solution is a bit of a kludge - in handling of trailing symlink (in lookup_last() and open_last_lookups() we clear nd->stack[0].name. That allows link_path_walk() to use the following rules when running out of a string to interpret: * if nd->depth is zero, we are at the end of pathname itself. * if nd->depth is positive, check the saved string; for nested symlink it will be non-NULL, for trailing symlink - NULL. It works, but it's rather non-obvious. Note that we have two sets: the set of symlinks currently being traversed and the set of postponed pathname tails. The former is stored in nd->stack[0..nd->depth-1].link and it's valid throught the pathname resolution; the latter is valid only during an individual call of link_path_walk() and it occupies nd->stack[0..nd->depth-1].name for the first call of link_path_walk() and nd->stack[1..nd->depth-1].name for subsequent ones. The kludge is basically a way to recognize the second set becoming empty. The things get simpler if we keep track of the second set's size explicitly and always store it in nd->stack[0..depth-1].name. We access the second set only inside link_path_walk(), so its size can live in a local variable; that way the check becomes trivial without the need of that kludge. Signed-off-by: -
Al Viro authored
Signed-off-by: -
Al Viro authored
old flags & WALK_FOLLOW <=> new !(flags & WALK_TRAILING) That's what that flag had really been used for. Signed-off-by: -
Al Viro authored
->last_type values are set in 3 places: path_init() (sets to LAST_ROOT), link_path_walk (LAST_NORM/DOT/DOTDOT) and pick_link (LAST_BIND). The are checked in walk_component(), lookup_last() and do_last(). They also get copied to the caller by filename_parentat(). In the last 3 cases the value is what we had at the return from link_path_walk(). In case of walk_component() it's either directly downstream from assignment in link_path_walk() or, when called by lookup_last(), the value we have at the return from link_path_walk(). The value at the entry into link_path_walk() can survive to return only if the pathname contains nothing but slashes. Note that pick_link() never returns such - pure jumps are handled directly. So for the calls of link_path_walk() for trailing symlinks it does not matter what value had been there at the entry; the value at the return won't depend upon it. There are 3 call chains that might have pick_link() storing LAST_BIND: 1) pick_link() from step_into() from walk_component() from link_path_walk(). In that case we will either be parsing the next component immediately after return into link_path_walk(), which will overwrite the ->last_type before anyone has a chance to look at it, or we'll fail, in which case nobody will be looking at ->last_type at all. 2) pick_link() from step_into() from walk_component() from lookup_last(). The value is never looked at due to the above; it won't affect the value seen at return from any link_path_walk(). 3) pick_link() from step_into() from do_last(). Ditto. In other words, assignemnt in pick_link() is pointless, and so is LAST_BIND itself; nothing ever looks at that value. Kill it off. And make link_path_walk() _always_ assign ->last_type - in the only case when the value at the entry might survive to the return that value is always LAST_ROOT, inherited from path_init(). Move that assignment from path_init() into the beginning of link_path_walk(), to consolidate the things. Historical note: LAST_BIND used to be used for the kludge with trailing pure jump symlinks (extra iteration through the top-level loop). No point keeping it anymore... Signed-off-by: -
Al Viro authored
kill nd->link_inode, while we are at it Signed-off-by: -
Al Viro authored
move the only remaining call of get_link() into pick_link() Signed-off-by: -
Al Viro authored
move get_link() call into step_into(). Signed-off-by: -
Al Viro authored
Move the call of get_link() into walk_component(). Change the calling conventions for walk_component() to returning the link body to follow (if any). Signed-off-by: -
Al Viro authored
After a pure jump ("/" or procfs-style symlink) we don't need to hold the link anymore. link_path_walk() dropped it if such case had been detected, lookup_last/do_last() (i.e. old trailing_symlink()) left it on the stack - it ended up calling terminate_walk() shortly anyway, which would've purged the entire stack. Do it in get_link() itself instead. Simpler logics that way... Signed-off-by: -
Al Viro authored
Fold trailing_symlink() into lookup_last() and do_last(), change the calling conventions of those two. Rules change: success, we are done => NULL instead of 0 error => ERR_PTR(-E...) instead of -E... got a symlink to follow => return the path to be followed instead of 1 The loops calling those (in path_lookupat() and path_openat()) adjusted. A subtle change of control flow here: originally a pure-jump trailing symlink ("/" or procfs one) would've passed through the upper level loop once more, with "" for path to traverse. That would've brought us back to the lookup_last/do_last entry and we would've hit LAST_BIND case (LAST_BIND left from get_link() called by trailing_symlink()) and pretty much skip to the point right after where we'd left the sucker back when we picked that trailing symlink. Now we don't bother with that extra pass through the upper level loop - if get_link() says "I've just done a pure jump, nothing else to do", we just treat that as non-symlink case. Boilerplate added on that step will go away shortly - it'll migrate into walk_component() and then to step_into(), collapsing into the change of calling conventions for those. Signed-off-by: -
Al Viro authored
Move restoring LOOKUP_PARENT and zeroing nd->stack.name[0] past the call of get_link() (nothing _currently_ uses them in there). That allows to moved the call of may_follow_link() into get_link() as well, since now the presence of LOOKUP_PARENT distinguishes the callers from each other (link_path_walk() has it, trailing_symlink() doesn't). Preparations for folding trailing_symlink() into callers (lookup_last() and do_last()) and changing the calling conventions of those. Next stage after that will have get_link() call migrate into walk_component(), then - into step_into(). It's tricky enough to warrant doing that in stages, unfortunately... Signed-off-by: -
Al Viro authored
Signed-off-by: -
Al Viro authored
New LOOKUP flag, telling path_lookupat() to act as path_mountpointat(). IOW, traverse mounts at the final point and skip revalidation of the location where it ends up. Signed-off-by: -
Al Viro authored
The following is true: * calls of handle_mounts() and step_into() are always paired in sequences like err = handle_mounts(nd, dentry, &path, &inode, &seq); if (unlikely(err < 0)) return err; err = step_into(nd, &path, flags, inode, seq); * in all such sequences path is uninitialized before and unused after this pair of calls * in all such sequences inode and seq are unused afterwards. So the call of handle_mounts() can be shifted inside step_into(), turning 'path' into a local variable in the combined function. Signed-off-by: -
Al Viro authored
Tells step_into() not to follow symlinks, regardless of LOOKUP_FOLLOW. Allows to switch handle_lookup_down() to of step_into(), getting all follow_managed() and step_into() calls paired. Signed-off-by: -
Al Viro authored
We need to dismiss a symlink when we are done traversing it; currently that's done when we call step_into() for its last component. For the cases when we do not call step_into() for that component (i.e. when it's . or ..) we do the same symlink dismissal after the call of handle_dots(). What we need to guarantee is that the symlink won't be dismissed while we are still using nd->last.name - it's pointing into the body of said symlink. step_into() is sufficiently late - by the time it's called we'd already obtained the dentry, so the name we'd been looking up is no longer needed. However, it turns out to be cleaner to have that ("we are done with that component now, can dismiss the link") done explicitly - in the callers of step_into(). In handle_dots() case we won't be using the component string at all, so for . and .. the corresponding point is actually _before_ the call of handle_dots(), not after it. Fix a minor irregularity in do_last(), while we are at it - if trailing symlink ended with . or .. we forgot to dismiss it. Not a problem, since nameidata is about to be done with (neither . nor .. can be a trailing symlink, so this is the last iteration through the loop) and terminate_walk() will clean the stack anyway, but let's keep it more regular. Signed-off-by: -
Al Viro authored
Current calling conventions: -E... on error, 0 on cache miss, result of handle_mounts(nd, dentry, path, inode, seqp) on success. Turn that into returning ERR_PTR(-E...), NULL and dentry resp.; deal with handle_mounts() in the callers. The thing is, they already do that in cache miss handling case, so we just need to supply dentry to them and unify the mount traversal in those cases. Fewer arguments that way, and we get closer to merging handle_mounts() and step_into(). Signed-off-by: -
Al Viro authored
... and make the callers of __follow_mount_rcu() use handle_mounts(). Signed-off-by: -
Al Viro authored
1) in case of __follow_mount_rcu() failure, lookup_fast() proceeds to call unlazy_child() and, should it succeed, handle_mounts(). Note that we have status > 0 (or we wouldn't be calling __follow_mount_rcu() at all), so all stuff conditional upon non-positive status won't be even touched. Consolidate just that sequence after the call of __follow_mount_rcu(). 2) calling d_is_negative() and keeping its result is pointless - we either don't get past checking ->d_seq (and don't use the results of d_is_negative() at all), or we are guaranteed that ->d_inode and type bits of ->d_flags had been consistent at the time of d_is_negative() call. IOW, we could only get to the use of its result if it's equal to !inode. The same ->d_seq check guarantees that after that point this CPU won't observe ->d_flags values older than ->d_inode update. So 'negative' variable is completely pointless these days. Signed-off-by:
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- 12 Mar, 2020 3 commits
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Al Viro authored
All callers are equivalent to path->dentry = dentry; path->mnt = nd->path.mnt; err = handle_mounts(path, ...) Pass dentry as an explicit argument, fill *path in handle_mounts() itself. Signed-off-by: -
Al Viro authored
... and shift filling struct path to just before the call of handle_mounts(). All callers of handle_mounts() are immediately preceded by path->mnt = nd->path.mnt now. Signed-off-by: -
Al Viro authored
same story as for atomic_open() in the previous commit. Signed-off-by:
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- 27 Feb, 2020 6 commits
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Al Viro authored
Currently it either returns -E... or puts (nd->path.mnt,dentry) into *path and returns 0. Make it return ERR_PTR(-E...) or dentry; adjust the caller. Fewer arguments and it's easier to keep track of *path contents that way. Signed-off-by: -
Al Viro authored
All callers of follow_managed() follow it on success with the same steps - d_backing_inode(path->dentry) is calculated and stored into some struct inode * variable and, in all but one case, an unsigned variable (nd->seq to be) is zeroed. The single exception is lookup_fast() and there zeroing is correct thing to do - not doing it is a pointless microoptimization. Add a wrapper for follow_managed() that would do that combination. It's mostly a vehicle for code massage - it will be changing quite a bit, and the current calling conventions are by no means final. Right now it takes path, nameidata and (as out params) inode and seq, similar to __follow_mount_rcu(). Which will soon get folded into it... Signed-off-by: -
Al Viro authored
O_CREAT | O_EXCL means "-EEXIST if we run into a trailing symlink". As it is, we might or might not have LOOKUP_FOLLOW in op->intent in that case - that depends upon having O_NOFOLLOW in open flags. It doesn't matter, since we won't be checking it in that case - do_last() bails out earlier. However, making sure it's not set (i.e. acting as if we had an explicit O_NOFOLLOW) makes the behaviour more explicit and allows to reorder the check for O_CREAT | O_EXCL in do_last() with the call of step_into() immediately following it. Signed-off-by: -
Al Viro authored
Only the address of ->total_link_count and the flags. And fix an off-by-one is ELOOP detection - make it consistent with symlink following, where we check if the pre-increment value has reached 40, rather than check the post-increment one. [kudos to Christian Brauner for spotted braino] Signed-off-by: -
Al Viro authored
1) no instances of ->d_automount() have ever made use of the "return ERR_PTR(-EISDIR) if you don't feel like mounting anything" - that's a rudiment of plans that got superseded before the thing went into the tree. Despite the comment in follow_automount(), autofs has never done that. 2) if there's no ->d_automount() in dentry_operations, filesystems should not set DCACHE_NEED_AUTOMOUNT in the first place. None have ever done so... Signed-off-by: -
Al Viro authored
Protection against automount/automount races (two threads hitting the same referral point at the same time) is based upon do_add_mount() prevention of identical overmounts - trying to overmount the root of mounted tree with the same tree fails with -EBUSY. It's unreliable (the other thread might've mounted something on top of the automount it has triggered) *and* causes no end of headache for follow_automount() and its caller, since finish_automount() behaves like do_new_mount() - if the mountpoint to be is overmounted, it mounts on top what's overmounting it. It's not only wrong (we want to go into what's overmounting the automount point and quietly discard what we planned to mount there), it introduces the possibility of original parent mount getting dropped. That's what 8aef1884 (VFS: Fix vfsmount overput on simultaneous automount) deals with, but it can't do anything about the reliability of conflict detection - if something had been overmounted the other thread's automount (e.g. that other thread having stepped into automount in mount(2)), we don't get that -EBUSY and the result is referral point under automounted NFS under explicit overmount under another copy of automounted NFS What we need is finish_automount() *NOT* digging into overmounts - if it finds one, it should just quietly discard the thing it was asked to mount. And don't bother with actually crossing into the results of finish_automount() - the same loop that calls follow_automount() will do that just fine on the next iteration. IOW, instead of calling lock_mount() have finish_automount() do it manually, _without_ the "move into overmount and retry" part. And leave crossing into the results to the caller of follow_automount(), which simplifies it a lot. Moral: if you end up with a lot of glue working around the calling conventions of something, perhaps these calling conventions are simply wrong... Fixes: 8aef1884 (VFS: Fix vfsmount overput on simultaneous automount) Signed-off-by:
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