LLAPI_LAYO...NDEX_RESET(3)

✨ LLAPI_LAYOUT_OST_INDEX_RESET ✨

okay so bestie, this is a page from the Lustre Library Functions manual (section 3, the library-call girlies) and it's literally about pressing the "undo" button on which OSTs your file lands on. let's get into it 💅

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🌸 NAME 🌸

llapi_layout_ost_index_reset — reset the OST index of all the Lustre file components. every single one. no crumbs left. 🧹

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🦋 SYNOPSIS 🦋

#include <lustre/lustreapi.h>

int llapi_layout_ost_index_reset(struct llapi_layout *layout);

one function, one argument, zero drama. iconic honestly. ✨

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💖 DESCRIPTION 💖

so like, here's the tea: llapi_layout_ost_index_reset() resets the starting ost_index number of all components in the file layout you hand it, and it sets them all to LLAPI_LAYOUT_DEFAULT. ✨

and why would you want that? because it lets the MDS automatically allocate the objects for each file component to the best OSTs available at that time. it's giving "let the algorithm pick, I trust her". 👑

this is your girl when you're copying an existing file layout — like one you retrieved using llapi_layout_get_by_fid(3), llapi_layout_get_by_fd(3), llapi_layout_get_by_path(3), or llapi_layout_get_by_xattr(3). call it so that your OST selection does not get copied exactly from the source layout, if that layout is going to be used with llapi_layout_file_open(3) to create a new file for migration, mirroring, or literally any other replication task. no cap: you don't want the source's exact OST picks riding along to the new file. 🫶

lowkey important: this is a "call it before you reuse that layout" situation. skipping it means the new file just inherits the source's OST choices byte for byte, and that's not what you want. 💀

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🔥 RETURN VALUES 🔥

llapi_layout_ost_index_reset() returns 0 on success — slay — or a negative error if something went wrong, and in that case errno is set appropriately. 😭

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💀 ERRORS 💀

• EINVAL — an invalid argument was specified. you passed something cursed, bestie. 🙈
• ENOENT — the layout does not have any valid components. it's empty. she's got nothing going on. 😭
• ENOMEM — insufficient memory to complete the operation. the vibes ran out of RAM. 💀

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🌈 AVAILABILITY 🌈

llapi_layout_ost_index_reset() is part of the lustre(7) user application interface library, and she's been serving since release 2.7.0. vintage but still main character. ⭐

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🎀 SEE ALSO 🎀

• llapi_layout_alloc(3)
• llapi_layout_file_open(3)
• llapi_layout_ost_index_set(3)
• llapi_layout(7)
• lustreapi(7)

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and that's the whole page, periodt. 💅 this lil' baddie ships as part of the Lustre User API, dated 2024-08-27, and you can find her filed under LLAPI_LAYO...NDEX_RESET(3). go reset some OST indices, you got this 🫶✨🌸