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optimize: added a tail pointer in mntinfo_add_list #2593

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optimize: added a tail pointer in mntinfo_add_list #2593

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44f9acb
optimize: make mntinfo_add_list O(1) by adding a tail pointer
ankushT369 Feb 7, 2025
bf8c2e8
optimize: added a tail pointer in mntinfo_add_list
ankushT369 Feb 7, 2025
679741f
optimize: added a tail pointer in mntinfo_add_list
ankushT369 Feb 7, 2025
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1 change: 1 addition & 0 deletions criu/include/mount.h
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Original file line number Diff line number Diff line change
Expand Up @@ -90,6 +90,7 @@ struct mount_info {
int deleted_level;
struct list_head deleted_list;
struct mount_info *next;
struct mount_info *tail;
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I think it is better to user the list_head structure here.

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@ankushT369 ankushT369 Feb 8, 2025 •
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You mean instead of mount_info *tail should I make it list_head tail

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I mean we can use the standard list here instead of reinventing a bicycle.

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@ankushT369 ankushT369 Feb 11, 2025 •
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I'm sorry if this conversation is taking long.. the thing is the list_head is of different type in order to store the tail of a struct mount_info* shouldn't we use the struct mount_info* type?? because in the code mount.c (where I have changed code) the struct mount_info *mntinfo was the single linked list as it was told in the comment (file : mount.c, line : 110) and the struct mount_info *new has to traverse the struct mount_info *mntinfo (file : mount.c, line : 122) in order to find the tail of it ( if the *mntinfo wasn't empty) thats why I created a struct mount_info* tail in order to hold the pointer to tail. Any node of type struct mount_info* can have its tail stored in it so that it can fetch in O(1) time. I know its reinventing a bicycle but the thing is I can't understand how can I use the struct list_head cause there is a mismatch in type in order to hold the tail of anything of type struct mount_info*. Maybe I can wrong here by misunderstanding what you tried to say you can rectify me I am a beginner currently learning things.

struct ns_id *nsid;

char *external;
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20 changes: 12 additions & 8 deletions criu/mount.c
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Original file line number Diff line number Diff line change
Expand Up @@ -113,21 +113,25 @@ struct mount_info *mntinfo;

static void mntinfo_add_list(struct mount_info *new)
{
if (!mntinfo)
if (!mntinfo) {
mntinfo = new;
mntinfo->tail = new->tail;
}
else {
struct mount_info *pm;

/* Add to the tail. (FIXME -- make O(1) ) */
for (pm = mntinfo; pm->next != NULL; pm = pm->next)
;
pm->next = new;
mntinfo->tail->next = new;
mntinfo->tail = new->tail;
}
}

struct mount_info *tail_buffer;

void mntinfo_add_list_before(struct mount_info **head, struct mount_info *new)
{
new->next = *head;
if(!*head)
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tail_buffer = new;

new->next = *head;
new->tail = tail_buffer;
*head = new;
}

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